A heterostructure containing several sheets of CdSe fractional monolayer quantum dots with nominal coverages of 0.5 and close to 0.25 of a monolayer (ML) embedded in a ZnSe matrix was successfully grown by a combination of submonolayer epitaxy and molecular beam epitaxy. Due to surface reconstruction properties of cation- and anion-terminated surfaces, one complete Cd–Se alternate source exposure cycle

Van der Waals layered GeTe/Sb2Te3 chalcogenide superlattices have demonstrated outstanding performance for use in dynamic resistive memories in what is known as interfacial phase change memory devices due to their low power requirement and fast switching. These devices are made from the periodic stacking of nanometer thick crystalline layers of chalcogenide phase change materials. The mechanism for

In this paper, the properties of Pd-based p-contacts on GaN-based laser diodes are discussed. Pd is often the metal of choice for ohmic contacts on p-GaN. However, for Pd/p-GaN ohmic contacts, nanovoids observed at the metal/semiconductor interface can have a negative impact on reliability and also reproducibility. The authors present a thorough analysis of the microstructure of the Pd/p-GaN interface

Managing the interaction of materials with insertion layers and nonconventional molecular beam epitaxy growth conditions allows for interfaces that are more precise but requires judicious examination of the multiple possible design variables. Here, we show a comparison between As- and Sb-containing insertion layers between Al and two binaries with different group V elements and demonstrate that antimonide

Recently, chalcogenide materials have exhibited ovonic threshold switching characteristics, improving their suitability as selector devices to effectively depress the sneak current in the cross-point array (CPA) structures. However, chalcogenides must be subjected to a firing process before they can exhibit the threshold switching behavior. The firing process causes operation problems with respect

AlN/GaN double-barrier resonant tunnel diodes have been grown by rf-plasma assisted molecular beam epitaxy at temperatures between 760 and 860 °C on metalorganic chemical vapor deposition-grown GaN templates with sapphire substrates. Room temperature negative differential resistance (NDR) was observed for all samples despite the presence of higher densities of threading dislocations in the device layers

Nanoimprint lithography (NIL) is one of the most promising nanofabrication techniques. Soft NIL has inherent advantages for conformal contact and uneven substrates. The demolding process of soft NIL is critical for obtaining high-fidelity replicas, especially of multidirectional nanostructures. In this paper, a demolding device for soft NIL is proposed to separate the polymer replica from the mold

Block copolymer (BCP) directed self-assembly (DSA) has been presented as a potential economically attractive enhancement to extend the capabilities of optical lithography for semiconductor manufacturing. One concern in DSA is the level of defectivity that can be achieved in such a process. Although entropic effects will always lead to some degree of defectivity, highly ordered structures with a low

The authors propose the use of a low-energy (sub-keV/atom) bismuth cluster ion beam for time-of-flight secondary ion mass spectrometry (TOF-SIMS). 2 keV Bi3+ at an incident angle of 65° generated bismuth-adducted secondary molecular ions [M + Bi]+, which are not observed under normal TOF-SIMS conditions. This low-energy Bi primary ion beam was used for the depth profiling of Irganox1010/Irganox1098

The authors drive a plasma-induced reduction reaction of the gold precursor by alternating current (AC)-driven atmospheric pressure plasma at the plasma-liquid interface. They systematically study the plasma-induced reaction at the plasma-liquid interface and observe that the reduction reaction is a proportionality relationship to the root mean square current of AC-driven atmospheric pressure plasma

Field emission scanning probe lithography (FE-SPL) is based on the exposure of a resist covered substrate with low energy electrons emitted from an ultra-sharp tip placed in close vicinity to a sample. GaN nanowires (NWs) present high mechanical stability, suitable geometry for FE-SPL, and controllable electrical properties achieved by adjusting dopant concentration. Here, the authors will present

The effect of metallic Mg insertion into the CoFeB/MgO/CoFeB-based magnetic tunnel junction (MTJ) on tunnel magnetoresistance (TMR) properties was investigated using synchrotron x-ray diffraction (XRD) in the out-of-plane geometry. For the MTJ without metallic Mg insertion, both low resistance area product (RA) and TMR ratio tend to decrease as the MgO barrier becomes thinner. When the 0.1-nm-thick

The apparent improvement of the depth resolution in secondary ion mass spectrometry depth profiles using cluster secondary ions (Me2+, Me3+) as compared to single ion profiles (Me+) is explained to be an artifact caused by an attractive interaction enhancing cluster formation. Successful application of the mixing-roughness-information depth model shows how different profiles are interconnected and

A new laser ionization method for sputtered neutral mass spectrometry (SNMS), which the authors call “dual-laser SNMS,” was developed to increase the ionization probability and improve sensitivity. In this technique, pulsed IR and UV lasers irradiated sputtered atoms simultaneously, while the additional UV laser pulse enhanced the ionization process. The useful yields of the target elements increased

Using ellipsometry for curved-surface characterization requires the knowledge of the surface normal vector in order to determine material-related surface parameters like refractive index, layer thickness, or birefringence of the surface material at the incidence point, because the recorded signal depends on both the (unknown) surface normal vector n → and material-related surface characteristics. It

The biggest advantage of time-of-flight secondary ion mass spectrometry (TOF-SIMS) is imaging performance. TOF-SIMS is the only surface analysis technique which can provide the elemental and molecular ion images with high spatial resolution and high sensitivity. However, acquiring accurate images of uniform intensity from three-dimensional (3D) objects having curved surfaces is challenging because

Secondary ion emission with MeV heavy ions provides a unique opportunity for insight into ion collisions and material analysis. MeV-energy ion beams excite electrons near the surface and enhance the ionization of high-mass molecules, enabling the acquisition of secondary ion mass spectrometry (SIMS) spectra of ionized molecules with suppressed fragments. The SIMS technique with MeV-energy heavy ions

The authors present a quantitative secondary ion mass spectrometry (SIMS) analysis of the useful ion yield of magnesium dopant in a gallium nitride matrix. A quadrupole SIMS instrument was used to analyze an Mg-doped GaN sample grown by metal organic chemical vapor deposition. Oxygen (O2+) was used as the primary ion beam and its energy was varied in the range from 0.5 to 5 kV with and without oxygen

Hydrogen behavior in tantalum and tantalum oxide thin films was examined using the in situ oxidation secondary ion mass spectrometry (in situ oxidation SIMS) method previously developed by the authors. Oxidation of Ta films by the introduction of O2 into the sputter deposition chamber immediately after film growth was found to reduce the amount of H absorbed in the Ta films by 2.7 times for samples

Due to their electrical and physical properties, Si1−XGeX materials are widely used in microelectronic devices. In particular, the Ge component found within Si1−XGeX compounds is important for enhancing carrier mobility and altering the lattice constant of metal-oxide-semiconductor field-effect transistors. In this study, magnetic sector secondary ion mass spectrometry (magnetic sector SIMS) and time-of-flight

Self-aligned double patterning (SADP), or spacer lithography, is a widely used technique in the semiconductor industry for high-throughput nanoscale pattern definition and thus is of great significance for very-large-scale integration, large-area photonic device fabrications, and other applications. In a standard SADP flow, chemical vapor deposition or atomic layer deposition is used to deposit a conformal

In nanoimprint lithography, a release agent on the mold surface is usually necessary for easy demolding between the mold and the imprinted (thermal) resist. In this work, the thermal stability of 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS) monolayers is studied using x-ray photoelectron spectroscopy. The FDTS monolayers are deposited on Si (100) substrates via vapor phase reactions. Significant

The use of any materials in particle accelerators requires a rigorous evaluation of their behavior in vacuum, especially when used at cryogenic temperatures. Laser treated copper substrates offer unquestionable advantages for electron-cloud mitigation purposes due to their low secondary electron yield. Here, the author investigates their vacuum behavior for the occurrence of small temperature transients

Recent studies have shown that it is possible to use ToF-SIMS to identify and quantify mosquito insecticides, such as permethrin and deltamethrin, on mosquito netting. The insecticide in those studies was incorporated in the netting fiber. Permethrin treated fabric is in common usage to provide mosquito repellent clothing and is the only approved insecticide for apparel. The insecticide is applied

Chemical imaging, such as mass imaging, provides a distribution image of a particular matter and is crucial for analyzing the chemical and physical mechanisms of a sample. However, methods that provide molecular or elemental distribution do not always have sufficiently high spatial resolution to evaluate the nanosized structures in a sample. To address this issue, a multimodal data analysis method

Although germanium (Ge) is a semiconductor frequently used in many facets of materials science, its optical applications are limited because of an indirect band structure, which significantly diminishes absorption and emission efficiency. However, sufficiently high levels of tin (Sn) alloying enable an indirect-to-direct band structure crossover, resulting in improved optical properties. Moreover,

Polypyridine-based ruthenium complexes are among the most interesting photoactive molecular systems, in virtue of a number of outstanding (photo)physicochemical properties. To exploit such properties in solid-state applications, such as molecular electronics, optoelectronics, and photovoltaics, tailored experimental strategies are needed for the anchoring of such complexes on surfaces. At the same

To facilitate the design of heterostructure devices employing hexagonal (sp2) boron nitride, x-ray photoelectron spectroscopy has been used to determine the valence band offsets (VBOs) at interfaces between amorphous hydrogenated sp2 boron nitride (a-BN:H) and atomic-layer-deposited high-dielectric-constant (high-k) aluminum oxide (Al2O3) and hafnium oxide (HfO2). After consideration of the effects

The demand for new biomaterials in several biomedical applications, such as regenerative engineering and drug delivery, has increased over the past two decades due to emerging technological advances in biomedicine. Degradable polymeric biomaterials continue to play a significant role as scaffolding materials and drug devices. Polyphosphazene platform is a subject of broad interest, as it presents an

The authors study the effect of etch chemistry and metallization scheme on recessed Au-free Ohmic contacts to AlGaN/GaN heterostructures on silicon. The effect of variation in the recess etch chemistry on the uniformity of Ohmic contact resistance has been studied using two different etch chemistries (BCl3/O2 and BCl3/Cl2). Experiments to determine the optimum recess etch depth for obtaining a low

An etching system based on the interaction of electrons extracted from a direct current hollow cathode (HC) Ar plasma and injected toward an Si3N4 covered silicon substrate located in the downstream reactive environment created by an additional remote CF4/O2 plasma source was developed and evaluated. By controlling the properties of the injected beam electrons, this approach allows to deliver energy

AlGaN polarization-doped field-effect transistors were characterized by DC and pulsed measurements from room temperature to 500 °C in ambient. DC current-voltage characteristics demonstrated only a 70% reduction in on-state current from 25 to 500 °C and full gate modulation, regardless of the operating temperature. Near ideal gate lag measurement was realized across the temperature range that is indicative

The composition of III–V semiconductor alloys with multiple group V elements results from a complex interaction of each group V species with each other and with group IIIs. Molecular beam epitaxy growth conditions, such as the group V absolute fluxes and flux ratios, substrate temperature, group III growth rate, the presence of surfactants, and the alloy's strain state, all affect the composition of

Ar-gas-cluster ion beam (GCIB) sputter collecting method was developed and applied for multiple organic analysis methods of a polymer thin layer. By using this method, a polyvinylpyrrolidone thin layer (50 nm thick) on a polyethylene terephthalate substrate film could be selectively collected and analyzed by pyrolysis-gas chromatography-mass spectrometry. Furthermore, it was also applied to molecular

Bi cluster ions are among the most utilized primary sources for time-of-flight secondary ion mass spectrometry (TOF-SIMS). Although Bi clusters have advantages over larger clusters, such as C60+ and Arn+, TOF-SIMS is less sensitive for macromolecules when Bi clusters are used as primary ions. Matrix-enhanced SIMS is a more sensitive technique for large molecules, because the matrix limits fragmentation

The authors report on phase resolved optical emission spectroscopy (PROES) measurements of pulsed capacitive coupled plasmas (CCPs) through argon. The PROES results indicate that under some conditions, the electron heating mechanism can be changed substantially from that dominant in continuous CCPs. The normally dominant α heating mode of electropositive plasmas can be aided by a drift-ambipolar (DA)

Low-temperature aluminum nitride (AlN) depositions were studied under low gas pressure conditions of 0.1 Pa. In order to operate under 0.1 Pa sputter-conditions, the magnetic mirror-type magnetron cathode (M3C) has been developed in the authors' studies. The plasma light-emission distributions generated by the M3C were observed at an input RF power of 5–100 W and an Ar gas pressure of 0.1–0.65 Pa.

Time of flight-secondary ion mass spectrometry (ToF-SIMS) has been used to obtain the composition in depth of a few nanometers thick layer of lanthanum aluminate prepared by molecular beam epitaxy. The electrical properties of the films were probed by piezoresponse force microscopy (PFM) and Kelvin Force Microscopy (KFM). From PFM images, the sample under study behaves exactly as if it was ferroelectric

Noncontact band edge thermometry based on diffuse reflectance was used to monitor and control the substrate temperature rise during the MBE growth of niobium nitride transition metal nitrides on transparent, wide-bandgap silicon carbide substrates. Temperature transients as large as 135 °C are induced by changing the main substrate shutter state. The growth of niobium nitride films as thin as ∼5 nm

GaP-based alloys can be grown lattice-matched to Si, making them an attractive choice for use in Si-based multijunction solar cells. This work focuses on the growth of GaP on Si with the aim to improve the surface quality of GaP. The Si wafers used in this study were of precise (001), (001) 4° offcut toward [110], and (001) 6° offcut toward [110] orientations. GaP of high crystalline quality was grown

This report introduces a method for fabricating graphene at low temperatures via chemical vapor deposition enabled by ultrathin (∼1 nm) nickel-gold (Ni-Au) catalysts. The unique combination of high carbon (C) solubility Ni, low C solubility Au, and an ultrathin layer of a catalyst demonstrates the effectiveness to produce graphene at 450 °C with the layer number independent of growth duration. In contrast

Titanium dioxide (TiO2) has a range of applications including catalysis, hydrogen production, and water purification. In this work, anatase TiO2 was annealed in vacuum at 800 °C, resulting in a conductive thin film. Exposure to subgap laser light (532 nm wavelength) caused a seven order-of-magnitude increase in resistance. Laser-irradiated regions showed an increase in optical transmission, consistent

Transition metal dichalcogenides such as MoS2 and WS2 are low-dimensional semiconductor materials. MoS2 and WS2 nanotubes and flakes were grown by a chemical transport reaction under a temperature gradient. I2 was used as a transport agent for previously synthesized MoS2 and WS2, respectively. These multilayered nanotubes are indirect bandgap semiconductors with a bandgap depending on their diameter

Transfer technology is now becoming very attractive not only for new technologies such as flexible technology but also for solid state technologies when performances are limited by technological barriers that have to be overcome. In this last context, the transfer of high electron mobility transistors (HEMTs) on diamond substrates represents an opportunity to improve the thermal dissipation when the

Resonant laser sputtered neutral mass spectrometry can greatly enhance the ionization efficiency of specific neutral sputtered atoms through resonant excitation using tunable laser(s). However, the laser beam cannot irradiate the entire volume where sputtered particles are moving, because the laser beam is focused. In contrast, for an extremely low concentration of target elements, it is necessary

We describe a technique for the fabrication of arrays of elastomeric pillars whose top surfaces are treated with selective chemical functionalization to promote cellular adhesion in cellular force transduction experiments. The technique involves the creation of a rigid mold consisting of arrays of circular holes into which a thin layer of Au is deposited while the top surface of the mold and the sidewalls

In order to detect diseases like cancer at an early stage while it still may be curable, it's necessary to develop a diagnostic technique which can rapidly and inexpensively detect protein and nucleic acid biomarkers, without making any sacrifice in the sensitivity. We have developed a technique, based on the use of bioactivated microfluidic channels integrated with electrodes for electrical sensing

We describe a high throughput patterning process used to create arrays of molecular-scale features for the study of cytoskeletal protein binding interactions. The process uses a shadow-evaporated metal mask to facilitate lift-off of features defined by nanoimprint lithography. This simple and robust approach alleviates difficulties in pattern transfer of ultra-small features and results in arrays of

We introduce a new scheme of nanocontact printing that fabricates nanoarrays using stamps generated by ultraviolet nanoimprint lithography. Array patterns can be generated by this printing technique in a high-density (number of features per unit area) fashion with a feature size as low as 30 nm and period of 100 nm. Sub-500 nm alignment accuracy for multilayer printing has been obtained using a traditional

Cells can secrete biotherapeutic molecules that can replace or restore host function. The transplantation of such cells is a promising therapeutic modality for the treatment of several diseases including type 1 diabetes mellitus. These cellular grafts are encapsulated in semipermeable and immunoisolative membranes to protect them from the host immune system, while allowing the transport of nutrients

The mechanical properties of a cell's environment can alter behavior such as migration and spreading, and control the differentiation path of stem cells. Here we describe a technique for fabricating substrates whose rigidity can be controlled locally without altering the contact area for cell spreading. The substrates consist of elastomeric pillar arrays in which the top surface is uniform but the

The authors report a polymeric based rib waveguide with U shape self-align fiber couplers system using a simple micromolding process with SU8 as a molding material and polydimethysiloxane as a waveguide material. The material is used for its good optical transparency, low surface tension, biocompatibility, and durability. Furthermore, the material is highly formable. This unique fabrication molding