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  • Growth and characterisation of MnSb(0001)/InGaAs(111)A epitaxial films
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-07-10
    P.J. Mousley, C.W. Burrows, M.J. Ashwin, A.M. Sánchez, V.K. Lazarov, G.R. Bell

    MnSb layers have been grown on In x Ga 1 - x As(111)A virtual substrates using molecular beam epitaxy (MBE). The effects of both substrate temperature ( T sub ) and Sb/Mn beam flux ratio ( J Sb / Mn ) were investigated. The surface morphology, layer and interface structural quality, and magnetic properties have been studied for a 3 × 3 grid of T sub and J Sb / Mn values. Compared to known optimal MBE conditions for MnSb/GaAs(111) [ T sub =415 ° C , J Sb / Mn =6.5], a lower substrate temperature is required for sharp interface formation when growing MnSb on In0.48Ga0.52As(111)A [ T sub =350 ° C , J Sb / Mn =6.5]. At high flux ratio ( J Sb / Mn =9.5) elemental Sb is readily incorporated into MnSb films. At higher substrate temperatures and lower flux ratios, (In,Ga)Sb inclusions in the MnSb are formed, as well as MnAs inclusions within the substrate. The Sb and (In,Ga)Sb inclusions are epitaxial, while MnAs inclusions are endotaxial, i.e. all have a crytallographic relationship to the substrate and epilayer. MBE optimisation towards different device structures is discussed along with results from a two-stage growth scheme.

    更新日期:2018-07-12
  • Continuous crystallization of α-form L-glutamic acid in an MSMPR-Tubular crystallizer system
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-07-10
    Zhenguo Gao, Yuanyi Wu, Junbo Gong, Jingkang Wang, Sohrab Rohani

    Continuous crystallization of active pharmaceutical ingredients is of prime significance. A continuous mixed suspension mixed product removal (MSMPR)-tubular crystallizer geometry is designed and optimized to produce the metastable α-form crystals of L-glutamic acid with uniform mean size of 130 microns. The MSMPR is used to produce well-tuned seed crystals that undergo further growth in a series of tubular crystallizers. The effects of the initial supersaturation, stirring speed, nucleation temperature and residence time were optimized in the MSMPR crystallizer to tune the supply of continuous seeds by using the principal component analysis and in-situ particle tracking measurement. The continuous seeds of the desired metastable polymorphic form with specific size ranging from 5.0 to 15.0 microns and number density ranging from 500 to 1500 counts, were transferred to a series of three coiled tubular crystallizers for further growth. In addition, the cooling strategy in the tubular crystallizers was utilized to further optimize the quality of the final crystal product. The crystal size distribution (CSD) in the MSMPR-tubular crystallizer system was compared with a single MSMPR with the same residence time and found to be superior. Finally, a potential scale up strategy of the MSMPR-tubular crystallizer system was proposed for further study.

    更新日期:2018-07-12
  • Anticalcification potential of heparin on hydroxyapatite seeds using a constant composition in vitro model
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-07-11
    Adel F. Badria, Petros Koutsoukos, Cristian D'Alessandro, Sotirios Korossis, Dimosthenis Mavrilas

    Calcification is among the principal causes of biological heart valve substitute failure. Glycosaminoglcans (GAGs) are negatively charged molecules, possessing anticoagulation and anti-inflammatory activity that make them a potential solution against calcification. In the present work, the anticalcification potential of heparin was investigated under constant supersaturation conditions with respect to hydroxyapatite (Ca5(PO4)3OH; HAP). Heparin concentration in the supersaturated solutions was in the range between 0.25-3 ppm, at pH 7.40 and 37°C. Heparin showed inhibitory activity, which was attributed to adsorption at the active crystal growth centres. Heparin concentration as low as ca. 50μM, reduced the rate of HAP crystal growth by more than 80%, while further increase (up to 200 μM) failed to completely inhibit the process beyond 90%. Heparin uptake studies at equilibrium conditions and analysis of the kinetics data in the presence of heparin, strongly suggest that the inhibition is due to the adsorption of heparin onto the HAP crystals, which resulted in the poisoning of the active growth sites.

    更新日期:2018-07-12
  • The influence of the substrate misorientation on the structural quality of GaN layers grown by HVPE
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-07-11
    Z. Liliental-Weber, R. dos Reis, T. Sochacki, M. Bockowski

    The paper describes a Transmission Electron Microscopy study on the structural quality of GaN samples grown by Hydride Vapor Phase Epitaxy (HVPE) on ammonothermal (Am) GaN seeds. The only difference between these samples is the crystallographic direction of misorientation of the Am GaN seeds for the further growth. The studied samples were 1° misoriented in two perpendicular crystallographic directions: the [1100] and the [1120]. Cross-section samples were studied and showed that growth of homo-epitaxial GaN on the substrate tilted toward the [1100] direction appeared to lead to lower defect density than those tilted toward the [1120] direction. This was associated with slow growth on {1011} planes that are oriented “edge-on” for the growth along [1120] direction leading to the formation of facets while the [1100] direction is devoid of such facets. The competition between slow and fast growth rates on particular planes would lead to the change of the crystal shape such as triangle or trapezoidal one. Our present study also found that cracks in the samples tilted toward the [1120] direction are formed and they are the origin for half loops. Moreover, dislocation propagation from these cracks is observed. Such cracks were not observed for the samples tilted toward the [1100] directions, probably due to more uniform growth. There were no dislocations at the sample surface. However, some parasitic growth occurred on the wafer edges for both samples. Cross-section microscopy found high dislocation density in these areas with and a majority of them are edge dislocations.

    更新日期:2018-07-12
  • Synthesis and electrical transport properties of Bi2O2Se single crystals
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-07-04
    Qianhui Mao, Xiaodong Geng, Jinfeng Yang, Junji Zhang, Shuangmei Zhu, Qiongyan Yu, Yuan Wang, Haidong Li, Ruixue Li, Haoshan Hao

    we have reported the synthesis, electrical resistivity ρ(T), Hall coefficient (RH) and magnetoresistance (MR) of Bi2O2Se single crystals with layered tetragonal structure (space group I4/mmm). The lattice parameters obtained after Rietveld refinement are a = b = 3.897Å, c = 12.237Å, respectively. ρ(T) and RH measured in the temperature range from 2 K to 300 K show high carrier concentration extrinsic semiconductor behavior. At higher temperatures (130–300 K), the resistivity is dominated by phonon scattering mechanism, as manifested by ρ(T) ∝T1.5. The magnetic field dependence of resistivity is positive in the whole temperature range. The MR at 2 K increase monotonically with magnetic field and manifest very weak saturate trend up to 9 T where it reaches its maximum value with Δρxx/ρxx≈100%.

    更新日期:2018-07-05
  • Stability of multiple Shockley type basal plane stacking faults in heavily nitrogen-doped 4H-SiC crystals
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-07-04
    Yuina Mannen, Kana Shimada, Chisato Taniguchi, Noboru Ohtani

    The stability of various types of multiple Shockley type basal plane stacking fault in heavily nitrogen-doped 4H-SiC crystals was theoretically investigated on the basis of the quantum well action (QWA) mechanism. The energy levels of confined electrons within multiple Shockley stacking faults (SSFs) were calculated using the simple quantum well model and compared to the experimental values estimated from photoluminescence measurements. The formation energies of the stacking faults were also calculated on the basis of the axial next nearest neighbor Ising (ANNNI) model for SiC polytypes. Based on these physical and electronic parameters, the stability of multiple SSFs in heavily nitrogen-doped 4H-SiC crystals was discussed, and it was revealed that the stacking sequence of multiple SSFs largely affects their stability; SSFs having a cubic stacking sequence of medium thickness (five to six Si-C bilayer thickness) are stable in heavily nitrogen-doped 4H-SiC crystals at the typical growth and device processing temperatures of SiC, i.e., 1500–2600K.

    更新日期:2018-07-05
  • Effects of ampoule coating technology on carbon film and GaSb crystals
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-07-04
    Xiao Gao, Shenqiu Zhai, Juncheng Liu, Donghai Yang, Weicai Zhang

    A carbon film was deposited on the inner wall of a quartz crucible by vacuum evaporation. The effects of gas pressure in the crucible on the carbon film surface morphology and the binding force between the carbon film and the inner wall of the quartz crucible were studied. When the gas pressure was increased from 4 Pa to 12 Pa, the surface roughness of the carbon film increased and large particles appeared on the surface, whereas the binding force between the carbon film and the inner wall of the crucible weakened. When the gas pressure was 12 Pa, the carbon film peeled off. GaSb crystal ingots were prepared by the vertical Bridgman method, and the effects of the carbon film on the ingots’ microstructure and properties were studied. When there was no carbon film on the inner wall of the crucible, the dislocation density of the crystals was the highest, their hardness and resistivity values were the largest, and their carrier mobility was the lowest. When the gas pressure was 4 Pa, the crystal surface was flat and the dislocation density of the crystals significantly decreased. The hardness and resistivity values also decreased and the carrier concentration significantly increased. When the gas pressure was 12 Pa, the hardness and resistivity values of the crystals gradually increased, whereas the carrier mobility gradually decreased.

    更新日期:2018-07-05
  • Interface control by rotating submerged heater/baffle in vertical Bridgman configuration
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-07-03
    A.G. Ostrogorsky, V. Riabov, N. Dropka

    Toroidal flow was used to control the shape of the solid-liquid interface, while growing NaNO3 crystals in vertical Bridgman configuration. The flow was driven by a disk-shaped rotating Submerged Heater/baffle (SH). The flow in the inner melt, below the rotating SH/baffle, closely resembles the flow in Czochralski melts. The experiments were conducted in a transparent furnace which allowed side view to the solid-liquid interface. Without baffle rotation, interface was concave. For zero growth rate, convex interface was obtained typically at 15 rpm. The degree of convexity increased with rotation rate. While growing NaNO3 at 3.5 mm/h and 5.5 mm/h, convex interface was maintained at 45 rpm. Detailed 3D CFD numerical simulations are in solid agreement with the NaNO3 experiments. The rotating baffle process is particularly useful for growing crystals of low thermal conductivity because flow, generated by baffle rotation, carries heat radially out bypassing slow conduction through the crystal.

    更新日期:2018-07-04
  • Te doping of GaAs and GaInP using diisopropyl telluride (DIPTe) for tunnel junction applications
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-07-04
    Gwénaelle Hamon, Nicolas Paillet, José Alvarez, Alexandre Larrue, Jean Decobert

    In this work, we have investigated the growth of highly n-doped gallium arsenide (GaAs) and gallium indium phosphide (GaInP) with tellurium (Te) by metal organic vapor phase epitaxy (MOVPE) using diisopropyl telluride (DIPTe), aiming at fabricating high performances tunnel junctions. A parametric study is performed in order to optimize the n++–type doping. Concentrations above 2.7×1019 cm-3 were achieved in both GaAs and GaInP layers. Using these Te-doped layers, we fabricated both n on p (n/p) and p on n (p/n) tunnel junctions. The p/n tunnel junction required additional annealing steps during growth, due to memory effect and surfactant properties of Te. We characterized GaAs/GaAs, GaAs/AlGaAs and AlGaAs/GaInP tunnel junctions with peak tunneling current densities as high as 250, 3000 and 1500 A/cm2 respectively. These tunnel junction performances are suitable for multijunction solar cells operating under high concentration.

    更新日期:2018-07-04
  • The urea-barbituric acid polymorphic co-crystal system: characterization, thermodynamics and crystallization
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-07-02
    Xiangyang Zhang, Jinsuo Yang, Yanyang Wu, Xinggui Zhou

    Polymorphism in co-crystals is known to have a dramatic effect on physiochemical properties. The current contribution covers the characterization, thermodynamic analysis, and cooling seeded crystallization investigation of the urea-barbituric acid (UBA) polymorphic co-crystal system including urea (UA), barbituric acid (BA), and two polymorphic UBA (Forms I and III). Supramolecular synthesis of UBA Forms I and III have been conducted by cooling crystallization in methanol and then systematically characterized by powder X-ray diffraction (PXRD), thermal analysis (DSC and TGA), Raman and IR spectroscopy. Compared to the TGA results, the exothermic and endothermic peaks shown in DSC curves represent the decomposition of UBA and the melting of BA, respectively. Using the measured solubility data, the UBA polymorphs were found to be an enantiotropic polymorphic system, and the transition points in the water and methanol were determined at 35 oC and 33 oC, respectively. Subsequently, the modified Apelblat equation and van’t Hoff model were used to correlate the experimental data and to calculate the dissolution enthalpy and entropy of the different system. Moreover, cooling seeded crystallization of two polymorphic co-crystals in methanol was carried out to investigate the influence of process variables, such as seed amount, cooling rate, and stirring rate, on the crystal structure and crystal size distribution of final co-crystals.

    更新日期:2018-07-02
  • Preparation of Cu2Sn1-xGexS3 bulk single crystals by chemical vapor transport with iodine
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-30
    Riki Fujita, Nobuo Saito, Kenichiro Kosugi, Kunihiko Tanaka

    Bulk crystals of monoclinic Cu2Sn1-xGexS3 were prepared by chemical vapor transport with iodine. The samples were investigated using electron-probe microanalysis, transmission electron microscopy, Raman spectroscopy and X-ray diffraction (XRD). All of the samples had a Cu-rich and S-poor composition. As the Ge content increased, the XRD peaks shifted to higher angle, the Raman peaks shifted to higher wavenumber, and the lattice constants decreased. Selected-area electron diffraction patterns showed that the samples were single crystal and had a monoclinic structure.

    更新日期:2018-07-01
  • Determination of the Crystallographic Orientation of SrI2 Crystals
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-30
    G. Calvert, S. Swider, F. Ruta, George Rossman, R.S. Feigelson

    Single crystals of strontium iodide (SrI2), an important material for nuclear detector applications, are grown commercially in cylindrical ampoules using the Bridgman self-seeding method. As a result, the axial orientation of Bridgman boules varies from run to run. Most crystal growth methods benefit from the use of oriented seeds, which can be helpful in maximizing growth rates and crystal quality. However, it is very difficult to orient SrI2 crystals because they are deliquescent and their surfaces damage easily during cutting and polishing. In this study, unpolished facets formed on an edge-defined film-fed growth (EFG) boule were used to generate the first Laue patterns. The principal boule used in this study had a square cross section and was grown using a seed cut from along the growth axis of a Bridgman boule. X-ray analysis showed that the EFG boule grown from this seed grew along the b-axis and the side facets were the (100) and (001) faces. This work made possible the fabrication of oriented SrI2 seeds for use in future EFG and Czochralski growth experiments and allowed for the determination of the optic axes using polarized light.

    更新日期:2018-07-01
  • Influence of HVPE Substrates on Homoepitaxy of GaN Grown by MOCVD
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-30
    J.K. Hite, T.J. Anderson, L.E. Lunet, J.C. Gallagher, M.A. Mastro, J.A. Freitas, C.R. Eddy Jr.

    The availability of high quality, free-standing GaN substrates enables new device applications in III-nitrides, especially for vertical device structures. With the introduction of these native substrates, the properties of nitrides are no longer dominated by defects introduced by heteroepitaxial growth. However, additional materials challenges are coming to the forefront that need to be understood and surmounted in order to allow homoepitaxial devices to achieve their full potential. In this paper, 2 μm of UID GaN are grown simultaneously by MOCVD on three commercially sourced 2” HVPE wafers. By doing so, the substrates are exposed to the exact same growth conditions and the influence of the substrate can be unambiguously identified. The results are presented in regards to the effects of the substrates on epitaxial film morphology, uniformity, impurity incorporation, substrate/epitaxy interface, and electrical properties.

    更新日期:2018-07-01
  • Hydrothermal synthesis of struvite and its phase transition: impacts of pH, heating and subsequent cooling methods
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-27
    A.P. Bayuseno, W.W. Schmahl

    MAP (magnesium, ammonium, and phosphate) precipitation under hydrothermal condition was investigated in the present study. The hydrothermal mediated solution of a MAP in equimolar ratios (1:1:1) was prepared for crystal growth in a reactor autoclave. In the hydrothermal experiments, the reactor was heated in a furnace at varying temperatures (60, 80 and 120 OC) for 24 h, and then followed by (i) air cooling and (ii) water quenching to room temperature. Struvite could be formed in the solution with initial pH values (7-10) when the reactor worked at 60 OC for 24 h and was subsequently air-cooled and water-quenched to room temperature. Working with the temperature of 80 OC and subsequent air cooling yielded struvite, dittmarite, and newberyite in the solution with pH values of 9 and 10. By heating reactor at temperatures of 80 and 120 OC and water quenching, however, a pure dittmarite could be grown in the solution with any pH values (7-10). Dittmarite was also the major phase precipitated in the solution with any pH condition at 120 OC for the longer reaction time (96 h). A small impurity of sylvite was unexpectedly co-precipitated in all processes. SEM micrograph showed that the crystal solids have irregular prismatic-shaped morphology. The optimal pH for MAP crystallization was predicted to be about 9. The present results provided valuable information for the understanding of phosphate recovery from effluent by the hydrothermal treatment.

    更新日期:2018-06-28
  • Real-time in situ observation of shear modulus evolution during Ostwald ripening of colloidal crystallization
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-28
    Hongwei Zhou, Shenghua Xu, Zhiwei Sun

    Real-time in situ observation of evolution of shear modulus during the crystallization and ripening of colloidal particles suspensions was conducted by using reflection spectrum and torsional resonance spectroscopy simultaneously. According to the structural information obtained by reflection spectrum, after the completion of nucleation, the crystallization can be basically divided into four stages: crystallization-dominated stage, crystallization and ripening coexistence stage, ripening-dominated stage and crystallization completion stage. Colloidal particles volume fraction significantly affects the duration of each stage. Our experiments showed that the ripening process is the main cause for the improvement of the mechanical strength (the increase of shear modulus). This observation is supposed to be associated with the diminishing of crystal interface as the result of the increase in crystallites size and the decrease in crystallites number during the ripening process. In addition, a theoretical analysis is given briefly on the softening effect induced by nonaffinity of disordered particles in interface region.

    更新日期:2018-06-28
  • Graph-based investigation of three-dimensional microstructure rearrangement during ternary eutectic directional solidification of Al-Ag-Cu
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-28
    Philipp Steinmetz, Johannes Hötzer, Anne Dennstedt, Christopher Serr, Britta Nestler, Amber Genau

    In order to control macroscopic material properties, it is important to understand the fundamental mechanisms of microstructure evolution during solidification. Varying the solidification velocity in eutectic alloys can result in both a change in microstructural length scale and different patterns. In a structure consisting of rods or fibers aligned in the growth direction, the adjustment mechanisms for this kind of pattern evolution consist of merging and overgrowing events for coarsening, and splitting and nucleation events for refinement. To gain a better understanding of these mechanisms during three-dimensional ternary eutectic solidification, the distribution of these four types of events is quantitatively assessed using graph based analysis of a three-dimensional data set obtained by synchrotron tomography of a solidified ternary eutectic Al-Ag-Cu alloy. The results demonstrate that the amount of microstructural change events is larger for higher growth velocities. It is found that the microstructure adjustment under steady growth conditions, i.e. constant composition, constant solidification velocity and constant temperature gradient, is dominated by splitting and merging events, while the coarsening due to a velocity decrease occurs by rod termination via overgrowth. The comparison of the microstructure rearrangement of samples with different patterns and constant growth conditions show that, depending on the growth velocity, certain microstructure arrangements have a lower tendency to rearrange. The quantitative analysis of the rearrangement mechanisms lead to a better understanding of the microstructure evolution in complex eutectic alloys.

    更新日期:2018-06-28
  • High-Temperature Corrosion of Inconel®Alloy 718, Haynes®282®Alloy and CoWAlloy1&2 in Supercritical Ammonia/Ammonium Chloride Solution
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-25
    Anna-Carina L. Kimmel, Thomas F. Malkowski, Steven Griffiths, Benjamin Hertweck, Thomas G. Steigerwald, Lisa P. Freund, Steffen Neumeier, Mathias Göken, James S. Speck, Eberhard Schluecker

    Corrosion of process equipment during ammonothermal synthesis at high temperature and pressure is still one of the big limitations of this process because of reduced crystal quality and safety issues. In this paper we present preliminary ammonothermal corrosion experiments with two Ni-base superalloys (Inconel®Alloy 718 and Haynes®282®Alloy) and two newly developed Co-base superalloys (CoWAlloy1&2) in a supercritical NH3/NH4Cl-solution (24 h/550 °C/105 MPa). After the experiment, the samples were analyzed by their mass change per initial surface area (specific weight change). Additionally, the morphological and elemental changes of the corrosion layers were evaluated. None of the investigated alloys developed a passivation layer and the corrosion layers were very fragile. In agreement with previous studies, the Ni-base alloys showed intergranular attack with severe general corrosive degeneration. Despite their high potential for high-pressure at high-temperature applications and in contrast to a ternary Co-Al-W-alloy, the investigated multinary Co-base alloys were strongly attacked, too. However, CoWAlloy2 presented the lowest specific weight change of the investigated alloys. Thus, it shows the best potential for application in acidic environment of the investigated alloys. Additionally, CoWAlloy2 proved good stability in a supercritical NH3/Na-solution (24 h/550 °C/93 MPa).

    更新日期:2018-06-27
  • In situ x-ray monitoring of transport and chemistry of Ga-containing intermediates under ammonothermal growth conditions of GaN
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-26
    S. Schimmel, P. Duchstein, T.G. Steigerwald, A.-C.L. Kimmel, E. Schlücker, D. Zahn, R. Niewa, P. Wellmann

    Formation and transport of Ga-containing intermediates are essential for ammonothermal bulk growth of GaN. In this work, in situ x-ray transmission measurements are established as a tool for monitoring face-selective dissolution of GaN crystals as well as the Ga-concentration in the fluid. The accuracy of concentration determination by x-ray transmission measurements is evaluated and the detection limit for dissolved species is estimated. The detection limit is given both as a gallium concentration and as an attenuation coefficient, thus, it can easily be transferred to other materials of interest. Face-selective ammonothermal etching is investigated for both ammonoacidic and ammonobasic mineralizers. Time- and space-resolved monitoring of the concentration of Ga-containing intermediates is demonstrated using NH4F mineralizer. The results are discussed with respect to the formation of Ga-containing intermediates and mechanisms of mass transport. Based on molecular dynamics simulations, the experimentally observed, unexpectedly low diffusion coefficient for the Ga-transporting species is ascribed at least partially to the diffusion of larger [GaxFy]3x-y aggregates.

    更新日期:2018-06-27
  • Catalyst-free Growth of Lateral InAs Nanowires
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-26
    H.L. Wang, W.Q. Wei, J.H. Wang, Q. Feng, S.Y. Wu, H.X. Yang, X.L. Xu, T. Wang, J.J. Zhang

    We demonstrate a catalyst-free method to grow lateral InAs nanowires on GaAs (100) substrate by means of molecular beam epitaxy. By applying pre-surface treatment under oxygen plasma, lateral InAs nanowires with lengths of 1 - 2 um and width of approximately 30 - 80 nm are epitaxial grown along [<img height="14" border="0" style="vertical-align:bottom" width="25" alt="View the MathML source" title="View the MathML source" src="https://origin-ars.els-cdn.com/content/image/1-s2.0-S0022024818302999-si1.gif">11¯0] direction. Stacking faults are not observed in the epitaxial process, which is usually an issue for InAs nanowires grown vertically on (111) substrates. Photo-luminescent measurements were performed for both single and multiple layers of InAs nanowires. A spectrum peak at the wavelength of 1625 nm is observed for a single wire at 5 K and room temperature emission is obtained for three layers of InAs nanowires. In addition, InAsSb nanowires are achieved along [110] direction, with a length of 0.4 - 0.8 μm and a width of 60 - 80 nm.

    更新日期:2018-06-27
  • Compositional control of gold-catalyzed ternary nanowires and axial nanowire heterostructures based on IIIP1-xAsx
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-27
    Vladimir G. Dubrovskii

    Ternary IIIP1-xAsx nanowires and axial heterostructures within such nanowires are perfect building blocks for optoelectronics in an important wavelength range. However, the full control over the morphology and composition of IIIP1-xAsx nanowires as well as the interfacial abruptness of axial In(As)P/InP nanowire heterostructures is not achieved so far. Here, we present a fully self-consistent model for the growth and composition of gold-catalyzed IIIP1-xAsx nanowires and nanowire heterostructures that explains and predicts interesting phenomena. In particular, we find that the phosphorous concentration in the quaternary Au-III-As-P droplet should be much smaller than that of arsenic under the typical growth conditions. This suppresses the indium crystallization rate when passing from the InAs to InP segment, leading to the droplet swelling. Special care should be taken to keep the droplet on top of the InP segment. We show that the InAs/InP interfacial abruptness is challenging, while the reverse InP/InAs switch should always be atomically sharp. The governing equations connecting thermodynamics and kinetics of ternary nanowires based on IIIP1-xAsx are used to formulate clear routes for the necessary compositional control, with possible extensions to other material systems.

    更新日期:2018-06-27
  • Study on the Influence of Lysozyme Crystallization Conditions on Crystal Properties in Crystallizers of Varied Sizes When Temperature is the Manipulated Variable
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-27
    Xi H. Tang, Jing J. Liu, Yang Zhang, Xue Z. Wang

    In this work, crystallization experiments were conducted in three different sizes of crystallizers (5 and 100 ml, and 1 L) to study the influence of temperature on the crystallization of lysozyme. Lysozyme solutions with concentrations of 40 and 30 g L-1 and 10% (w/w) NaCl were used. The temperature was reduced from 20 to 0 °C with various cooling rate and stirring speed. The data indicated that crystallization with cooling but without agitation or with agitation but without cooling led to low yield and inconstancy between batches, whereas that with combined cooling and agitation resulted in tetragonal crystals with high yields. Parameters, including crystallization onset, crystal morphology, crystal size distribution, concentration, supersaturation, and yield were examined by in situ and ex situ observations. The observations within small cooling rate range of 0.030 - 0.111 °C min-1 indicated that minor changes in cooling rate could cause significant differences in these parameters. The comparison with thermostatic experiment showed that cooling could cause the crystal sizes to be widely dispersed. While high cooling rate lead shorter crystallization onset time and higher supersaturation, thereby result in larger crystal size, higher tendency of aggregation and wider crystal size distribution, low cooling rate can pose a great challenge to the temperature control in scale-up crystallization. The work also demonstrated that the crystallization conditions obtained from 5- and 100-ml crystallizers, from which well-defined crystals with high yields were obtained, could successfully be reproduced in 1-L crystallizer.

    更新日期:2018-06-27
  • Crystal Growth and Evaluation of Nitrogen and Aluminum Co-Doped N-type 4H-SiC Grown by Physical Vapor Transport
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-20
    H. Suo, K. Eto, T. Ise, Y. Tokuda, H. Osawa, H. Tsuchida, T. Kato, H. Okumura

    N-type 4H-SiC crystals were grown by the physical vapor transport (PVT) method with nitrogen and aluminum (N–Al) co-doping. By using aluminum carbide powder preannealed in nitrogen gas atmosphere as an aluminum doping source, we obtained highly N–Al co-doped crystals with a nitrogen concentration higher than that in nitrogen-only-doped crystals. The dislocation densities of N-Al co-doped crystals with a high aluminum concentration (> 1 × 1019 cm-3) were found to become higher than those with a low aluminum concentration (< 1 × 1019 cm-3). Moreover, we investigated the expansion velocities of double Shockley-type stacking faults (DSFs) in the N–Al co-doped and the nitrogen-only-doped crystals. We found that the DSF expansion velocities in the N–Al co-doped crystals were lower than those in the nitrogen-only-doped crystals. This difference in the DSF expansion velocity is discussed with respect to the quantum well action model.

    更新日期:2018-06-22
  • Growth and physical properties of Bi2Sr2CaCu2O8+x crystals grown by a simple pressure technique and comparison with regrowth self-flux technique
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-21
    Neeraj K. Rajak, Trupti S. Gaikwad, Amrutha Mukundan, P. Manju, Arya Mohan, Dharmendra K. Singh, A. Thamizhavel, D. Jaiswal-Nagar

    Single crystals of a high temperature superconductor Bi2Sr2CaCu2O8+x (2212) were grown using two different techniques, namely, regrowth technique as well as a pressure technique and the results are compared. Single crystal x-ray diffraction (XRD) performed on crystals grown using both techniques show no impurity or intergrowth phase. However, powder XRD reveals the presence of only Bi2Sr2CuO6+x(2201) intergrowth phase in crystals grown using pressure technique, with additional impurity phases also found in the crystals grown using regrowth technique. Rietveld refinement showed the weight fraction of 2212 as 93% % in crystals grown from pressure technique, confirming the excellent quality of the as-grown crystals. The transition temperature of crystals grown using both techniques was ∼ ∼ 90 K. It was found that pressure technique gives crystals that have a higher superconducting volume fraction (∼ ∼ 100) than that of crystals grown using regrowth technique. Structural and magnetization measurements reveal that the as-grown crystals grown using pressure technique are of high quality, comparable to those grown using traveling solvent floating zone technique. Crystals grown by both the techniques exhibit second magnetization peak anomaly.

    更新日期:2018-06-22
  • Growth Mechanism of Polycrystalline CsI(Tl) films on Glass and Single Crystal Si Substrates
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-21
    Lina Guo, Shuang Liu, Tianyu Wang, Xiaochuan Tan, Rongguo Lu, Shangjian Zhang, Yong Liu, Zhiyong Zhong, Charles M. Falco

    The microstructure morphology and crystal quality of CsI(Tl) films are influenced by the crystal properties of substrates. In this work, CsI(Tl) films on the glass and single crystal silicon substrates are fabricated by vacuum thermal evaporation at a low deposition rate. The microstructure morphology, crystalline quality and scintillation properties of the films were examined by using scanning electron microscopy, X-ray diffraction, photoluminescence and radioluminescent spectrum. To study the growth mechanism of CsI(Tl) films on amorphous and monocrystalline substrates, a growth model based on the classical Volmer-Weber (VW) growth mode are proposed. During the film growing, the wetting and not-wetting phenomena of the clusters appear on the glass and Si(111) substrates respectively. In addition, the microcrystalline columns with different orientations are modeled to explain the surface morphology deteriorate of the CsI(Tl) film with 3 μm thickness on Si(111) substrate.

    更新日期:2018-06-22
  • Numerical investigation of the effect of static magnetic field on the TSSG growth of SiC
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-19
    Lei Wang, Takashi Horiuchi, Atsushi Sekimoto, Yasunori Okano, Toru Ujihara, Sadik Dost

    A set of numerical simulations were conducted to investigate the effect of applied static magnetic field on the convective flows and carbon concentration in the Top-Seeded Solution Growth (TSSG) process of SiC. The applied magnetic field is considered as vertical and cusp in an axisymmetric configuration. Seed rotation was also included in the simulations. The numerical results show that the applications of VMF (vertical magnetic field) and weak CMF (cusp magnetic field) are effective in suppressing Marangoni convection. The application of VMF slows down growth rate but reduces the variation of growth rate towards a more constant rate. Seed rotation appears to be not beneficial in the presence of CMF alone. However, the combined effect of seed rotation with VMF enhances growth and makes the growth rate variation smaller.

    更新日期:2018-06-20
  • Nucleation and islands growth of CdZnTe(001) epitaxial films on GaAs(001) substrates by Close Spaced Sublimation
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-18
    Kun Cao, Wanqi Jie, Gangqiang Zha, Tingting Tan, Yingrui Li, Ruiqi Hu

    The early stages of close spaced sublimation growth of CdZnTe(001)/GaAs(001) epilayer were experimentally studied under different substrate temperatures and ambient pressures. SEM, AFM, XRD, EBSD and EDS were used for the characterization of morphology, structure and composition of the films. The films were found to be (001) oriented and epitaxial in nature with zinc blende cubic structure. Deposition models were used to explain the correlation between growth condition and CdZnTe island morphology. Films grown at 350 °C and 1×102 Pa show the best uniform and smooth surface. When increasing substrate temperature to 430 °C or ambient pressure to 1×104 Pa or 3×104 Pa, islands are less compact and exhibit preferential growth along one of <110> directions, which could be resulted from the big lattice mismatch (14.0%) of Cd0.9Zn0.1Te(001)/GaAs(001) heterojunction. For the growth at 430 °C in 3×104 Pa, prior nucleation at defect site was found, and the appearance of regular <010> oriented island edges proposes that steps <010>{100} are more stable for CdZnTe(001)/GaAs(001) epilayer than steps <110>{111}.

    更新日期:2018-06-18
  • Protrusions reduction in 3C-SiC thin film on Si
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-12
    Massimo Zimbone, Marco Mauceri, Grazia Litrico, Eric Gasparo Barbagiovanni, Bongiorno Corrado, Francesco La Via

    We present a study for large defects called protrusions that form during the hetero-epitaxy of SiC on Si. We focus first on surface morphology, size, three-dimensional shape and internal structure, and second on photoluminescence and Raman features. These defects have a peculiar 3D structure similar to inverted square pyramids with a vertex close to the SiC/Si interface. The size of the square and the height of the pyramid are both related to the thickness of the epi-layer and are spatially limited by the stacking faults in the {111} planes. The inner core of the defect consists of nano crystals twinned with respect to the substrate orientation. The defects demonstrate broad peculiar emission band at about 750 nm, while the usual photoluminescence signal from band recombination is at 520 nm. The SiC/Si interface is studied in order to investigate the seed of protrusion defect formation. We found that seeds responsible for the formation of protrusions lie 10 nm above the SiC/Si interface. This indicates that protrusion forms after the carbonization process, in particular in the temperature ramp up after carbonization. Modifying the Si/C ratio and some other growth parameters in the post-carbonization process we succeed in reducing the density of protrusion to less than 10 cm-2.

    更新日期:2018-06-13
  • Effects of Fe-Ni solvent with different Fe contents on the boron concentration in colorless diamonds
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-08
    Liangchao Chen, Xinyuan Miao, Xuemei He, Longsuo Guo, Shuai Fang, Yao Wang, Zhanke Wang, Chao Fang, Hongan Ma, XiaoPeng Jia

    In this paper, high-quality colorless diamonds were successfully synthesized by temperature gradient method (TGM) in China-type cubic anvil high-pressure apparatus (CHPA) at 6.0 GPa and 1340 °C. High-purity graphite was used as carbon source and the Fe-Ni alloys with different Fe contents were used as the solvent-catalyst for diamond synthesis. The effects of Fe content (high-Fe-type and low-Fe-type) on boron concentration were specially investigated. All the colorless diamonds exhibit the typical boron-related absorption peaks of 2802 cm-1 in infrared (IR) absorption spectra, but the boron concentrations are different. Compared with the low-Fe-type alloy solvent, it is more difficult for boron atoms to incorporate into diamond lattice in high-Fe-type alloy solvent system. This work provides a new approach to control the boron concentration in colorless diamonds and synthetic high-purity diamond crystal.

    更新日期:2018-06-08
  • X-ray and Raman determination of InAsSb mole fraction for x <0.5
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-07
    K. Murawski, K. Grodecki, D. Benyahia, A. Wysmolek, B. Jankiewicz, P. Martyniuk

    InAsSb epilayers grown on GaAs substrates by molecular beam epitaxy have been studied using X-ray diffraction and Raman scattering. X-ray diffraction was used to determine the mole fraction of presented samples. In Raman spectrum, we analyzed for each sample not only the position of LO InAs and InSb phonons but also intensities of those. We found correlation between intensities ratio of LO phonons and the mole fraction of measured samples and we proposed a method how to calculate InAsSb mole fraction only using Raman spectroscopy.

    更新日期:2018-06-07
  • Influence of solvent properties and intermolecular interaction between solute and solvent on nucleation kinetics of HMBTAD
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-07
    Yongfan Yang, Ling Zhou, Xia Zhang, Wenchao Yang, Shihao Zhang, Lixuan Xiong, Yu Wei, Meijin Zhang, Baohong Hou, Qiuxiang Yin

    The induction time of HMBTAD was measured in four pure ester solvents and acetone + acetonitrile binary solvent mixtures at 283.15K with different supersaturation. The wide variation of induction time shows the stochastic nature of nucleation process and can be expressed as the Poisson distribution. In ester solvents, the nucleation rate is the largest in methyl acetate and the smallest in isobutyl acetate, with ethyl acetate and propyl acetate in between. Adding acetone to the supersaturated solution of acetonitrile makes the nucleation rate slower. The calculated interfacial energy of HMBTAD in pure ester solvents increases in the order: methyl acetate < ethyl acetate < propyl acetate < isobutyl acetate. In acetone + acetonitrile binary solvent mixtures, the interfacial energy increases with the increase of the mole fraction of acetone. It is interesting to find that the interfacial energy can be correlated to the solubility data and the dielectric constant in different solvents with high accuracy. In addition, the influence of intermolecular bonding between the solute and the solvent on the nucleation difficulty has been further evaluated and analyzed based on the Raman spectra of crystal and saturated solution of HMBTAD.

    更新日期:2018-06-07
  • On questionable ferroelectric and piezoelectric properties in single crystals
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-05
    Zbigniew Tylczyński, Aram M. Petrosyan, Bikshandarkoil R. Srinivasan

    In this short review, a critical analysis of the purported ferroelectric and piezoelectric properties of crystals which have been published is critiqued.

    更新日期:2018-06-06
  • Facile synthesis of α-MnO2 nanorods and their electrochemical performances
    J. Cryst. Growth (IF 1.742) Pub Date : 2007-02-08
    Hong-en Wang, Dong Qian, Zhouguang Lu, Yujie Li, Ruijing Cheng, Wei Zhang

    Single-crystalline α-MnO2 nanorods have been successfully prepared via in situ hydrothermal decomposition of single KMnO4 under different acidic conditions. The as-synthesized products were characterized with X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), selected area electron diffraction (SAED), high-resolution transmission electron microscope (HRTEM), and Fourier transformation infrared spectroscopy (FT-IR). The effects of various experimental conditions on the phase structures and morphology of the final products were investigated. Formation mechanism for the MnO2 nanorods was discussed on the basis of the experimental results. The results show that the usage and kinds of acids used in the experiments can influence the phase of the final products considerably. Phase-pure α-MnO2 nanorods can be obtained in a wide temperature range from 100 to 150 °C. Electrochemical studies of the MnO2 materials prepared at 150 °C for different hydrothermal times indicate that the MnO2 materials prepared for 5 and 8 h show fine capacitive behaviors and high specific capacitances of 83.9 and 79.3 F/g, respectively.

    更新日期:2018-06-03
  • Growth and characterization of directionally solidified eutectic systems for scintillator applications
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-02-27
    Akira Yoshikawa, Kei Kamada, Shunsuke Kurosawa, Yuui Yokota, Akihiro Yamaji, Valery I. Chani, Yuji Ohashi, Masao Yoshino

    Fabrication of scintillating eutectic composites by various directional solidification techniques is introduced and discussed in some details. Number of methods widely practiced for the single crystal growth including Czochralski, Bridgman or vertical zone melting, and micro-pulling-down are also acceptable for the production of eutectic materials. Two types of such materials are considered here. These are (1) composites used for neutron scintillators; eutectic materials that consist of high neutron cross section material and efficient scintillator (they do not require regular micro-structure) and (2) high resolution scintillators; eutectic materials that have well ordered rod/fiber structure of one of the phases immersed into matrix of second phase (one of them should be efficient scintillator). In later one, the wave guiding can be established in one of the phases (either matrix or fibers). The composites with fiber structure are supposed to be very promising substances for detecting initial irradiation with high spatial resolution. LiF/LiYF4 and LiF/CaF2:Eu eutectic composites represent first group of the scintillators, but CsI/NaCl and GdAlO3/α-Al2O3 correspond to the second one.

    更新日期:2018-06-03
  • The role of hydrogen in carbon incorporation and surface roughness of MOCVD-grown thin boron nitride
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-06-02
    Piotr A. Caban, Dominika Teklinska, Pawel P. Michalowski, Jaroslaw Gaca, Marek Wojcik, Justyna Grzonka, Pawel Ciepielewski, Malgorzata Mozdzonek, Jacek M. Baranowski

    Boron nitride films were grown on 2-inch sapphire substrates using the MOCVD technique. The growth was performed using a pulsed source injection mode with triethylborane (TEB) and ammonia (NH3) with a high V/III ratio, which corresponds to the self-terminated growth mode. Two different carrier gases, H2 and Ar, were used to investigate their influence on the growth mechanism, while all the other growth parameters were kept the same. The BN films thus obtained were examined using XRR, SIMS, Raman spectroscopy, ATR spectroscopy, SEM and AFM. A difference was found in the surface roughness. The BN films grown in an H2 atmosphere had a surface roughness three times smoother than those grown in Ar. However, the main difference was brought to light by SIMS measurements. The SIMS measurements revealed that growth under an H2 flow leads to a reduction in carbon concentration by more than four orders of magnitude. It was also shown that the boron distribution in the BN film grown under an H2 flow is very uniform. It is discussed that this mechanism is related to the reactions between TEB and NH3 in the presence of H2. The elimination of carbon by using hydrogen reveals its role in BN growth, which is indeed essential.

    更新日期:2018-06-02
  • Thermal expansion, luminescence, and scintillation properties of CaMoO4 crystals grown by the vertical Bridgman method
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-30
    Shangke Pan, Jianyu Zhang, Jianguo Pan, Guohao Ren, Jooyoung Lee, Hongjoo Kim

    CaMoO4 crystal is a promising scintillator for investigating the neutrinoless double beta decay process and is commonly grown by the Czochralski method. In this study, CaMoO4 single crystals were grown by the vertical Bridgman method using both spontaneous crystallization and seed crystal approaches. The CaMoO4 crystal grown using the spontaneous crystallization approach exhibited yellow, light blue, and deep blue colours (from top to middle part of the ingot). The thermal expansion coefficients, αa and αc, were calculated to be 6.11 × 10-5/°C, and 23.58 × 10-5/°C, respectively. The optical transmission spectra and photo- and thermally stimulated luminescence spectra of the crystals before and after thermal annealing were also investigated. The yellow cubic CaMoO4 crystal showed the highest x-ray-stimulated luminescence intensity and the best light output under the excitation of a 137Cs radioactive source.

    更新日期:2018-05-31
  • Analysis of screw dislocation mediated dark current in Al0.50Ga0.50N solar-blind metal-semiconductor-metal photodetectors
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-30
    Shashwat Rathkanthiwar, Anisha Kalra, Rangarajan Muralidharan, Digbijoy N. Nath, Srinivasan Raghavan

    We report on a billion-fold reduction in reverse-bias leakage current density (11.3 A/cm2 to 8.5 nA/cm2 at 20 V) across Schottky contacts made to Al0.50Ga0.50N epilayers grown on sapphire. Interdigitated back-to-back Ni/Au Schottky contacts were made to unintentionally doped Al0.50Ga0.50N epilayers grown by metal organic chemical vapor deposition to realize photodetectors with metal-semiconductor-metal geometry. Testing on a self-consistent series of samples grown under different conditions revealed that a two-order reduction in screw dislocation density is primarily responsible for the significant reduction in the lateral leakage (dark) current. This observation is validated by conductive atomic force microscopy experiments. Analytical modelling by temperature-dependent current-voltage measurements confirm a screw dislocation mediated carrier transport mechanism. The anomalously high reverse-bias leakage current (μA-mA) in the highly defective samples is found to be dominated by thermionic field emission (TFE) at low biases and Poole-Frenkel emission (PFE) from a deep donor level at high biases. With a significant improvement in the crystalline quality, a solar-blind photodetector with an EQE of 47 %, photo/dark current ratio of 1.4 x 105 and transient characteristics of < 20 ms is demonstrated. This study towards understanding the leakage in Al0.50Ga0.50N is expected to benefit the development of various deep-UV devices and GaN-AlGaN based power transistors.

    更新日期:2018-05-31
  • Crystal growth of off-stoichiometric Co2Cr1-xAl1+x Co 2 Cr 1 - x Al 1 + x Heusler compounds: Avoiding the solid state miscibility gap
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-31
    A. Omar, F. Börrnert, M. Haft, S. Hampel, W. Löser, B. Büchner, S. Wurmehl

    Co2CrAl is predicted as a promising candidate for half-metallic ferromagnetism. Unfortunately, synthesis of the stoichiometric composition is a challenge as the samples prepared so far using various techniques suffer from formation of secondary phases and consequently anomalous physical properties. Off-stoichiometric compounds have been explored as a possible approach to avoid the secondary phase precipitation. The Co2Cr0.8Al1.2 Co 2 Cr 0.8 Al 1.2 , Co2Cr0.6Al1.4 Co 2 Cr 0.6 Al 1.4 and Co2Cr0.4Al1.6 Co 2 Cr 0.4 Al 1.6 compositions were synthesized using Floating Zone (FZ) technique as they melt incongruently. The secondary phase fraction was reduced as Cr was partially substituted by Al. FZ-grown Co2Cr0.4Al1.6 Co 2 Cr 0.4 Al 1.6 was obtained as a single phase, signifying that the composition is out of the two-phase region. Furthermore, combining the data with an earlier work on annealing of spinodally decomposed samples, valuable insight into the extent of immiscibility was obtained.

    更新日期:2018-05-31
  • In-situ growth of CdS nanobelts by anealing Cd foil at H2S atmosphere
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-29
    Zelu Wei, Ziyi Gan, Xingming Yang, Ligang Ma, F.M. Zhang, X.S. Wu

    We report here a simple in-situ methodology to grow CdS nanobelts on Cd foil via annealing under H2S/N2 flux. The maximum size of CdS nanobelt reaches 4μm in width and 200μm in length. CdS nanobelts crystallize in wurtzite structure, growing along (10 View the MathML source 1 ¯ 0) direction. Grain boundaries in Cd foil induce the formation of the mesh pattern structure overwide the surface. And the cluster structure of CdS nanbelts is a result of rapid reaction between H2S and liquid form Cd outpouring through loopholes on the surface.

    更新日期:2018-05-30
  • The preparation and characterization of quasi-one-dimensional lead based perovskite CsPbI3 crystals from HI aqueous solutions
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-28
    Bin-Bin Zhang, Bao Xiao, Songtao Dong, Yadong Xu

    Quasi-one-dimensional lead based perovskite CsPbI3 exhibits increasing interests in quantum dots, solar cells, etc. However, high quality large CsPbI3 bulk crystals are still unexplored. Here we report CsPbI3 crystal growth from HI aqueous solution by tailoring the solubility. The morphology and crystal structure of CsPbI3 are characterized by SEM and XRD, which reveal the stick-like structure with the space group Pnma and lattice parameters a=10.46 Å, b=4.80 Å, and c=17.78 Å. Ultra violet-visible transmission spectra substantiate CsPbI3 being a direct-gap semiconductor with a band-gap ∼2.69 eV. In addition, a broad emission at 550∼580 nm with a large Stokes shift of 0.60∼0.75 eV and the corresponding dissociation energy 7.58 meV was found using temperature and power dependent PL spectra. This emission was attributed to a strong electron−phonon coupling induced “self-trap excitons” in CsPbI3. Our finding shields more light on the crystal growth, structure and optical properties of CsPbI3.

    更新日期:2018-05-29
  • A New Polymorph of Fenofibrate Prepared by Polymer- mediated Crystallization
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-29
    Xiangjun Shi, Yinghua Shao, Xiaoxia Sheng

    The polymer-mediated crystallization is an effective means to control the drug crystal. This project was focusing on a new form of Fenofibrate (Form IV) obtained by polymer-mediated crystallization. Medical polymer materials such as Hydroxy Propyl Methyl Cellulose (HPMC), Sodium Carboxyl Methyl Cellulose (CMC-Na) and Polyvinylpyrrolidone (PVP) were tested in this study. The powder X-ray Diffraction (PXRD), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and Fourier Transform Infrared Spectroscopy (FTIR) were used to differentiate the new form and other known forms. Material studio was applied to solve structures of Form IV. These polymorphic forms present different physicochemical properties. The crystallization conditions of Form IV were also detected. The study disclosed the Form IV has a low melting point of 65 °C and it is more stable compared with other metastable forms. This new form was proved to be more soluble in 0.5% tween-80 solution, which suggested it has highly potential to generate medicinal crystal.

    更新日期:2018-05-29
  • Formation of modulated structures induced by oxygen vacancies in α-Fe2O3 nanowires
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-29
    Tao Li, Honglei Feng, Yiqian Wang, Chao Wang, Wenhui Zhu, Lu Yuan, Guangwen Zhou

    Two modulated structures caused by long-range ordering of oxygen vacancies have been observed in α-Fe2O3 nanowires (NWs) produced after oxidation of Fe, one being ten times ( View the MathML source 30 3 ¯ 0 ) interplanar spacing and the other being six times ( View the MathML source 11 2 ¯ 0 ) interplanar spacing. Both types of oxygen vacancy ordering structures have a similar modulation periodicity of 1.45 or 1.50 nm with corresponding atomic ratios of Fe and O (Fe/O) of 0.7407 and 0.7273, respectively. The Fe/O ratios in the NWs with oxygen-vacancy ordering are very close to that of Fe3O4 (0.7500). The similar Fe/O ratio between NWs and Fe3O4 may explain the similar modulation periodicity of different oxygen-vacancy orderings. Electron energy-loss spectroscopy studies show that the Fe/O ratio of NWs is close to that of Fe3O4 when oxygen atoms are not sufficient, which makes the NWs energetically favorable. The elucidation of the mechanism governing the formation of the modulated structures in α-Fe2O3 NWs is critical for controlling the microstructure and correspondingly physicochemical properties of NWs.

    更新日期:2018-05-29
  • Optimized Optical Vapor Supersaturated Precipitation for Time-Saving Growth of Ultrathin-Walled ZnO Single-Crystal Microtubes
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-29
    Shuopeng Hu, Yinzhou Yan, Qiang Wang, Yue Lu, Yue Wang, Yijian Jiang

    Here we report growth of <0001>-oriented ultrathin-walled ZnO single-crystal microtubes with diameter of 75-250 μm and facet wall of <500 nm in thickness by optimized optical vapor supersaturated precipitation (OVSP). The mechanism of ultrathin-walled microtube formation during OVSP is revealed. The presintering temperature of precursor rod in the range of 600-800°C is found to be critical to achieve the complete hexagonal cross-sectional geometry of microtube. The facet wall is then thinned down to ∼450 nm with the temperature holding time increasing during OVSP under the lamp power of 60%@6000 W. The ultraviolet photoluminescence indicates the exciton-exciton collisions (i.e. p-band) boosted in the ultrathin-walled ZnO microtube boosting. Considering the time-consuming process in presintering of precursor rod in the Molysili furnace, the in-situ optical vapor supersaturated precipitation (IOVSP) is developed, in which the optical presintering is first performed in the image furnace using the lamp power of 30%@6000 W for 6 hours and then the lamp power is directly increased to 60%@6000 W for microtube growth by OVSP. The cooling process and transfer of precursor rod from the Molysili furnace to the image furnace are eliminated and the growth time can therefore be saved 56.7%. The finished microtube demonstrates a perfect hexagonal cross section with smooth surface and thin facet wall of ∼500 nm enhancing exciton-exciton collisions. The present work provides a time-saving in-situ method to grow high-quality ultrathin-walled ZnO single-crystal microtubes served as optical microcavities in the future for the applications in micro/nanophotonics.

    更新日期:2018-05-29
  • Additive induced pseudo-homoepitaxy of nanoneedles on NaCl crystals
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-24
    Melian A.R. Blijlevens, Eleanor R. Townsend, Willem J.P van Enckevort, Jan A.M Meijer, Elias Vlieg

    Additives and impurities often strongly influence the growth and shape of crystals, sometimes in an unexpected way. Heteroepitaxial growth of 3D guest crystals on different substrate crystals leads to a variety of surface patterns as has commonly been reported. Homoepitaxial growth, on the other hand, generally proceeds by layer by layer growth and leads to flat surfaces with steps. In our study we found that applying a droplet of ethanol with traces of triamide additive on a (001) NaCl substrate surface results in a 3D pseudo-homoepitaxial pattern comprising of ultrathin NaCl needles ordered in a “Mondriaan-like” arrangement. This is a consequence of small amounts of water in the ethanol, absorbed from the ambient, dissolving NaCl from the substrate, followed by poisoning the substrate surface by additive adsorption, which inhibits NaCl regrowth later on. At the last phase of droplet evaporation the NaCl supersaturation becomes very high and epitaxial crystal needles develop, starting from several oriented 3D nuclei on the poisoned substrate surface. This leads to a network of epitaxial NaCl needles each pointing toward one of the four perpendicular <100> directions on the (001) NaCl substrate. This peculiar phenomenon of 3D pseudo-homoepitaxy results from a subtle interplay between crystal dissolution, additive blocking and final growth at high supersaturation.

    更新日期:2018-05-25
  • Hall Characterization of epitaxial GaSb and AlGaAsSb layers using p-n junctions on GaSb substrates
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-24
    F Predan, J Ohlmann, S Mrabet, F Dimroth, D Lackner

    The Hall Van-der-Pauw method is widely used to assess the electrical properties of GaSb based semiconductor layers. Semi-insulating GaSb substrates are not available, and therefore, Hall structures are generally grown on semi-insulating GaAs. The lattice mismatch of 7.8 % between GaAs and GaSb results in high defect densities, which may influence the measurement. We investigated an alternative approach for Hall effect measurements using a p-n junction for the electrical isolation of the test layer from layers below. This allows antimonide based test layers with low defect density grown lattice-matched on GaSb substrates to be analyzed. Negligible leakage currents across the p-n junctions are key to ensure significant measurement results. n- and p-GaSb layers show similar carrier concentration if grown on GaSb or semi-insulating GaAs, with the exception of highly n-doped layers > 5 x 1017 cm-3. However, majority carrier mobilities were systematically higher on GaSb substrate, explained by a lower density of structural defects. Furthermore, the sample design with p-n junction enabled Hall effect measurements of quaternary p-Al0.2Ga0.8As0.02Sb0.98 layers, which was impossible for those same layers grown on GaAs due to strain induced phase-separation. The methodology is presented for antimonides, but it is applicable to a wide range of material systems including metamorphic structures.

    更新日期:2018-05-25
  • Single crystal growth and temperature dependent behaviors of melilite type piezoelectric crystal Ca2Al2SiO7
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-25
    Chao Jiang, Yong Long, Fapeng Yu, Lingfeng Kong, Feifei Chen, Shiwei Tian, Lifeng Qin, Xiufeng Cheng, Xian Zhao

    High temperature piezoelectric crystals are desired for sensing at elevated temperatures. In this work, a large size (2 inches) and low cost Ca2Al2SiO7 (CAS) crystal was grown by using the Czochralski pulling method. Thermal expansion coefficients α11 and α33 were measured and found to be on the order of 5.70×10-6/oC and 10.12×10-6/oC, respectively. The electrical resistivities of the CAS crystal along the X- and Z- directions at 700°C were found to be 3× × 107 and 2× × 108Ω Ω ·cm, respectively. The electro-elastic constants were evaluated by using the impedance and pulse-echo methods, where the piezoelectric coefficients d14 and d36 were determined to be 6.7 and 2.8 pC/N at room temperature, respectively. Moreover, the temperature dependence of the electro-elastic properties of the CAS crystal was investigated. The variation of elastic compliances was found to be <6% over the tested temperature range of 20∼700°C. The optimum crystal cuts with the maximum longitudinal and thickness shear piezoelectric coefficients for the CAS crystal were predicted, where the largest longitudinal piezoelectric View the MathML source d 11 ∗ (3.1pC/N) was achieved for the (XYtl)45o/-55o crystal cut, and the largest shear piezoelectric View the MathML source d 26 ∗ (4.7pC/N) was found for the (YXl)45o crystal cut, nearly two times that of α-quartz.

    更新日期:2018-05-25
  • Investigation on crystal growth and characterization of organic nonlinear optical triphenylmethane single crystal by vertical Bridgman technique
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-24
    T. Arivazhagan, S. Siva Bala Solanki, Rajesh Narayana Perumal

    An organic triphenylmethane (TPM) single crystal of length 58 mm and diameter 12 mm was grown by vertical Bridgman technique. The cell parameters of the grown crystal were confirmed by single crystal X-ray diffraction studies. Powder X-ray diffraction analysis was used to determine the crystalline nature of the triphenylmethane crystal. The functional groups of the triphenylmethane crystal were identified by Fourier transform infrared analysis. The linear optical property of the grown triphenylmethane crystal was studied by UV–Vis–NIR spectroscopic analysis which shows that the crystal has low cutoff wavelength at 281 nm and exhibits optical band gap value at 4.15 eV. The fluorescence spectrum indicates that the grown crystal emits blue light. The second harmonic conversion efficiency of the crystal was determined using Kurtz and Perry powder technique. The thermal property of the grown crystal was analysed using thermo gravimetric analysis, differential thermal analysis and differential scanning calorimetry. The dielectric constant, dielectric loss and AC conductivity of the grown crystal was investigated for different frequency range upto 1 MHz at various temperatures. The strength of the crystal was estimated by Vicker’s hardness test and laser damage studies.

    更新日期:2018-05-24
  • Structure, phase composition, and some properties of melt grown GaSe:Er crystals
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-24
    E.B. Borisenko, A.V. Timonina, D.N. Borisenko, V.I. Nikolaichik, A.N. Tereshchenko, N.N. Kolesnikov

    Powder and polycrystals synthesized from Ga, Se, Er components, as well as GaSe and GaSe:Er single crystals grown from melt in argon atmosphere and in vacuum, respectively, are studied. The growth and quenching conditions used in this work provide 2.5 times increase in solubility of erbium in GaSe matrix and a decrease in number of phases to GaSe and Er2Se3, oppositely to multiphase GaSe:Er alloys known from literature. For the first time Er2Se3 phase was detected by XRD in GaSe crystal doped with 1 at%Er. Possible orientation relations are derived for Er2Se3/GaSe epitaxial pair. It has been shown that stretched reflections in electron micro diffraction patterns and scattering of maximums in x-ray diffraction patterns are bound to stacking faults, which appear owing to thin interlayers of δ-GaSe polytype in ε-GaSe matrix of the melt-grown crystals. Morphology of growing crystal surface is studied. Photoluminescence spectra of pure and erbium-doped GaSe display intense photoluminescence bands, which are, presumably, associated with defect states in band gap of GaSe. It is shown that doping with Er has a strong effect on photoluminescence intensity and on its spectral composition. The measured 1.7 times increase in Vickers microhardness (up to 400 MPa) with respect to pure GaSe is due to solid solution hardening and to precipitation.

    更新日期:2018-05-24
  • Solution growth of a deuterated trans-stilbene crystal for fast neutron detection
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-22
    M.L. Carman, A.M. Glenn, A.N. Mabe, F.D. Becchetti, S.A. Payne, N.P. Zaitseva

    The paper reports results on growth and characterization of the first deuterated analog of the trans-stilbene crystal. The high optical quality stilbene-d12 single crystal was grown by application of the solution technique using specially synthesized raw material and an aromatic solvent (anisole). Optical, physical, and scintillation properties of the new material are compared to those of the regular trans-stilbene crystal. The new deuterated material is promising for use in fast neutron spectroscopy without the need for time-of-flight measurements.

    更新日期:2018-05-23
  • The temperature dependence of the pre-exponential factor and interfacial energy for aqueous glycine solutions based on the metastable zone width data
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-18
    Lie-Ding Shiau

    The metastable zone width (MSZW) data for aqueous glycine solutions at various saturation temperatures 308-328K are experimentally measured using the turbidity probe in this work. The integral model based on classical nucleation theory is applied to determine the pre-exponential factor and interfacial energy using the measured MSZW data. It is found that the MSZW data of aqueous glycine solutions are fitted well to the integral model. The results indicate for glycine that the interfacial energy decreases with increasing temperature while the pre-exponential factor increases with increasing temperature. For comparison, self-consistent Nyvlt-like equation and classical 3D nucleation theory approach are also applied to determine the nucleation kinetics of glycine from the measured MSZW data.

    更新日期:2018-05-18
  • Effect of MACE Parameters on Length of Porous Silicon Nanowires (PSiNWs)
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-18
    Nisha Singh, Mihir Kumar Sahoo, P.G. Kale

    Silicon nanowire-based devices have properties such as optical, electronic, and physical that can outperform their traditional counterparts in various ways because the silicon nanowires (SiNWs) have a high surface Si area to volume ratio and unique quasi-one-dimensional (1D) electronic structure. A variety of approaches are being classified into top-down and bottom-up methods to fabricate SiNWs. The present work demonstrates the synthesis of porous SiNWs (PSiNWs) through the metal-assisted chemical etching (MACE). The MACE produces PSiNWs using an aqueous solution composed of hydrofluoric acid (HF) and hydrogen peroxide (H2O2). Effect of MACE parameters such as H2O2 concentration, etching time, and Si wafer resistivity variation on the morphological characteristics (especially length) of PSiNWs are compared and thoroughly discussed. The structure and morphology of PSiNWs are characterized by transmission electron microscopy (TEM), environmental scanning electron microscopy (ESEM), and X-ray diffraction (XRD). The XRD data show the PSiNWs crystal growth direction.

    更新日期:2018-05-18
  • Controlled Growth and Atomic-scale Characterization of Two-dimensional Hexagonal Boron Nitride Crystals
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-17
    Amin Azizi, Mohammed Abu AlSaud, Nasim Alem

    Two-dimensional (2D) hexagonal boron nitride (h-BN) is a fascinating material for variety of applications such as graphene-based devices, transparent/bendable electronics, and deep ultraviolet emitters. However, its technological applications are contingent upon tunable and scalable growth. Here, we demonstrate reproducible and tunable growth of high-quality h-BN crystals on Cu via chemical vapor deposition (CVD) through a precise control of the BN precursor’s flow during growth. We present synthesis of both epitaxially-grown triangular flakes and large-area continuous films with tunable thickness ranging from monolayer to 11-layer thick. Using a combination of electron microscopy imaging, spectroscopy, and diffraction analysis, we thoroughly study morphology, thickness, chemistry, grain size, and atomic structure of the grown h-BN crystals. This study could pave the way for developing controlled and reproducible growth of high-quality h-BN crystals with tunable thickness and morphology.

    更新日期:2018-05-17
  • Low temperature liquid phase growth of crystalline InSe grown by the temperature difference method under controlled vapor pressure
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-15
    Chao Tang, Yohei Sato, Tadao Tanabe, Yutaka Oyama

    Indium selenide (InSe), which is one of the most promising layered III-chalcogenide compounds, is an attractive material for applications in infrared detection, solar energy conversion and high mobility transfer devices etc. In this work, InSe crystals were grown from the liquid phase using the temperature difference method under controlled vapor pressure (TDM-CVP) at a growth temperature of 582 °C, which is lower than that of the melt used in the Bridgman-Stockbarger technique. X-ray diffraction (XRD) and Raman spectroscopy results indicate that the grown crystal was γ-InSe with R3m space group symmetry. Photoluminescence measurements were carried out to determine the optical properties of the grown crystal, from which it was confirmed that the sample had a direct bandgap of 1.32 eV, an indirect bandgap of 1.28 eV and an exciton binding energy of 20 meV.

    更新日期:2018-05-15
  • Effect of Al3+ on Crystal Morphology and Size of Calcium Sulfate Hemihydrate: Experimental and Molecular Dynamics Simulation Study
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-15
    Hao Fan, Xingfu Song, Tianjie Liu, Yanxia Xu, Jianguo Yu

    Changes of crystal morphology and size of calcium sulfate hemihydrate (HH) by Al3+ ions, synthesized by hydrothermal method, were carried out to understand the interaction mechanism between the metal ion and crystal surface. The preferential adsorption of Al3+ on the top crystal surface was confirmed by XPS and ICP-OES, and the interaction mechanism was evaluated by molecular dynamics (MD). It was observed that the Al3+ ions significantly inhibited the HH growth along c-axial. The shape of HH crystal with the increasing of Al3+ ions concentration (0 to 10 mM), changed from whiskers to short rod-like. The position of Al3+ ions into the structure by molecular dynamics simulation showed preferential adsorption on active sites of (002) face, which inhibited the growth rate and leaded to the formation of short rod-like HH. This provided a guide for the research of calcium sulfate whiskers preparation from industrial gypsum.

    更新日期:2018-05-15
  • Anomalous eutectics in intermediately and highly undercooled Ni-29.8at.%Si eutectic alloy
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-15
    Fan Zhang, Cun Lai, Jianbao Zhang, Yachan Zhang, Qing Zhou, Haifeng Wang

    The transition from regular eutectics to anomalous eutectics is a well-known non-equilibrium phenomenon for undercooled eutectic alloys, the mechanism of which has been studied extensively but is still controversial. In this work, a Ni-29.8at.%Si eutectic alloy, as an ideal modeling system whose eutectic products are two stoichiometric intermetallic compounds, whose rapid solidification does not suffer any phase-selection and whose transformation path does not include any solid-state phase transformation, was undercooled by a melt fluxing technique and observed in-situ by a high-speed camera. A common transition from uncoupled eutectics to anomalous eutectics and a unique transition from uncoupled coarse lamellar-eutectics to anomalous eutectics were found at intermediate and high undercooling, respectively. The formation of coarse lamellar-eutectics is highly related to the abrupt increase of growth velocity at ΔT≈149 K, which is accompanied by a transition from dual-recalescence to single-recalescence. An electron back-scattering diffraction analysis shows that epitaxial growth of the second δ-Ni2Si phase on the primary γ-Ni31Si12 phase follows a particular eutectic orientation relationship. Anomalous eutectics were concluded to be formed by uncoupled eutectic growth with the reduction of interfacial energy but not chemical superheating as the driving force.

    更新日期:2018-05-15
  • Improved quality of In0.30Ga0.70As layers grown on GaAs substrates using undulating step-graded GaInP buffers
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-14
    Kuilong Li, Wenjia Wang

    High quality In0.30Ga0.70As layers on GaAs substrates were obtained using compositional undulating step-graded Ga1-xInxP (x=0.48-0.78) buffers grown by metal-organic chemical vapor deposition. The density of threading dislocation is about 4.0×106 cm-2 and the root-mean-square roughness is only 5.20 nm, which is much better than those grown on the conventional step-graded metamorphic buffer. On one hand, the reversed GaInP layers reduce the distribution imbalance of α dislocations between the (111) and (-1-11) slip planes, which promote dislocation glide. On the other hand, the inserted tensile strained GaInP layers change the direction of dislocation glide and facilitate dislocation annihilations, which effectively confine the threading dislocations in the buffer. Overall, this work provides a promising way to obtain virtual substrates for the achievement of desired metamorphic devices.

    更新日期:2018-05-15
  • Assessing the growth window of stannous oxide by ion beam sputter deposition (IBSD)
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-12
    M. Becker, F. Michel, A. Polity, P.J. Klar

    SnOx films were fabricated on soda-lime glass and sapphire substrates by reactive ion beam sputter deposition (IBSD). A detailed growth series on c -plane sapphire was prepared using heater temperatures from room temperature to 600° 600 ° C with different oxygen-to-argon ratios to investigate the impact of those parameters on thin film characteristics. By applying X-ray diffraction analysis and Raman spectroscopy an operating window was defined, in which SnO was grown without inclusions of parasitic Sn-related phases. The chemical bonding of the films was examined by X-ray photoelectron spectroscopy (XPS). Only a very narrow regime of oxygen flux was found with a composition close to stoichiometry. Furthermore, variation of the composition in SnO1±δ SnO 1 ± δ as well as the growth temperature were found to influence the morphology of the grown layer. The surface morphology was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). An average grain size of ≈10 ≈ 10 -50 nm was revealed for films grown at 200° 200 ° C, which increases for annealed samples and samples grown at elevated temperatures. In addition to the expected influence on grain growth and surface roughness, disintergation of the SnO crystallites was found for inappropriate oxygen flux and heater temperature, giving way to incorporation of Sn or SnO2 species.

    更新日期:2018-05-12
  • Rapid synthesis of alpha calcium sulfate hemihydrate whiskers in glycerol-water solution by using flue-gas-desulfurization gypsum solid waste
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-10
    Weili Teng, Jinshu Wang, Junshu Wu, Yucheng Du, Xin-Jian Jia, Hongyi Li, Tianning Wang

    The feasibility of fabricating alpha calcium sulfate hemihydrate (α-CSH) whiskers by using flue-gas-desulfurization (FGD) gypsum as source materials was studied. Crystal phase- and morphology-controlled crystallization of gypsum were realized in the designed glycerol-water reaction system. L-glutamic acid was found to accelerate the conversion of calcium sulfate dihydrate (CSD) into α-CSH whiskers by intercalating into layered CSD structure. The time-dependent experiments indicate rod-like CSD first splits into layered structure and then fascicular structure and finally single crystals. The splitting crystallization owing to lattice expansion of CSD generates α-CSH whiskers with a high aspect ratio (∼1:200). The facile method to convert FGD gypsum solid waste into CSD and finally α-CSH whiskers may prove particularly useful in the design of recyclable FGD gypsum with significant environmental impact, and it is particularly important in environmental remediation and green economics.

    更新日期:2018-05-10
  • The effect of ultrasonic treatment on the mechanisms of grain formation of as-cast high purity zinc
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-09
    B. Nagasivamuni, Gui Wang, David H. StJohn, Matthew S. Dargusch
    更新日期:2018-05-09
  • Molecular dynamics simulation of interfacial growth of SiC from Si–C solution on different growth planes
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-07
    Taka Narumi, Yasushi Shibuta, Takeshi Yoshikawa

    A critical issue in solution growth of 4H–SiC crystal is to control the morphology at the growth interface. We conducted a molecular dynamics simulation of interfacial growth of SiC from Si–C solution to understand the atomic-scale growth behavior on the different growth planes of 3C–SiC, 4H–SiC and 6H–SiC. The growth rates on the basal plane were smaller than those on the other planes. To understand the growth modes on the growth planes, calculations of growth behavior on the 4H–SiC View the MathML source { 0001 } , View the MathML source { 10 1 ‾ 0 } and View the MathML source { 10 1 ‾ 2 } were performed with larger cells. The growth interface of 4H–SiC View the MathML source { 10 1 ‾ 0 } and View the MathML source { 10 1 ‾ 2 } tended to become rough, whereas 4H–SiC View the MathML source { 0001 } maintained a flat interface. Possible growth modes were estimated from a correlation between the growth rate and the crystal structure.

    更新日期:2018-05-07
  • Influence of Substrates and Rutile Seed Layers on the Assembly of Hydrothermally Grown Rutile TiO2 Nanorod Arrays
    J. Cryst. Growth (IF 1.742) Pub Date : 2018-05-05
    Julian Kalb, James A. Dorman, Alena Folger, Melanie Gerigk, Vanessa Knittel, Claudia S. Plüisch, Bastian Trepka, Daniela Lehr, Emily Chua, Berit H. Goodge, Alexander Wittemann, Christina Scheu, Sebastian Polarz, Lukas Schmidt-Mende

    Rutile TiO2 nanorod arrays (NRAs) are applicable in various prospective technologies. Hydrothermal methods present a simple technique to fabricate such NRAs. In this report, we present the fabrication of seed layers for the hydrothermal growth of rutile TiO2 nanorods via sputter deposition, electron-beam evaporation, and sol-gel method and study the influence of each on growth behavior. To satisfy the requirements of numerous applications, p-type silicon, platinum, levitating carbon membranes, a template made of polystyrene spheres, and commercial fluorine tin oxide (FTO) were employed as substrates. We document the structural properties of the TiO2 seed layers and describe the relationship between the characteristics of the seed crystals, the growth evolution, and the appearance of as-grown nanorods. Various growth stages of rutile TiO2 nanorods are compared depending on whether they are grown on polycrystalline TiO2 or FTO seed layers. In both cases, a homogenous TiO2 bottom layer is formed at the seed layer/substrate interface, which is essential for electronic applications such as hybrid solar cells. Detached NRAs illustrate the effect of rutile FTO and TiO2 on the porosity of this bottom layer. Further details about the formation process of this layer are obtained from the growth on confined seed layers fabricated by electron-beam lithography.

    更新日期:2018-05-06
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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