Analysis on the temperature dependent electrical properties of Cr/Graphene oxide-Fe3O4 nanocomposites/n-Si heterojunction device

https://doi.org/10.1016/j.diamond.2020.107933Get rights and content

Highlights

  • The GO-Fe3O4 nanocomposite films were fabricated and characterized by XRD, SEM and AFM analysis.

  • The Cr/n-Si/Al and the Cr/GO-Fe3O4/n-Si/Al heteojunction devices were fabricated and their device performances were studied.

  • The device performance of Cr/GO-Fe3O4/n-Si/Al heterojunction was evaluated by the analysis of I-V characteristics.

  • The Cr/GO-Fe3O4 /n-Si/Al heterojunction device has a high potential to be used in thermal sensor applications.

Abstract

In this study, the Cr/n-Si/Al and Cr/Graphene oxide-Fe3O4 nanocomposites (GO-Fe3O4)/n-Si/Al heterojunction devices were fabricated and their Schottky diode performances were studied comparatively. In the first step, the GO-Fe3O4 nanocomposites were synthesized and the film characterization was carried out via XRD, SEM and AFM analysis methods. The results showed that the performance of the Cr/GO-Fe3O4/n-Si/Al device was better than that of Cr/n-Si/Al. For example, experimental ideality factors and the barrier heights were determined as 3.75 and 0.70 eV for Cr/n-Si/Al while they were found as 1.28 ve 0.63 eV for Cr/GO-Fe3O4/n-Si/Al heterojunction device. Next, we examined the electronic properties of the Cr/GO-Fe3O4/n-Si/Al heterojunction device as a function of temperature and the device performance of Cr/GO-Fe3O4/n-Si/Al heterojunction was evaluated by the analysis of I-V characteristics. To examine the electrical features of Cr/GO-Fe3O4/n-Si/Al heterojunction device, I-V measurements were studied between 100 K and 360 K in steps of 20 K. Next, the device parameters such as barrier height, ideality factor and series resistance were calculated by using Thermionic Emission (TE) and Cheung method. As a result of these measurements, it was found that the barrier height and ideality factor of the Cr/GO– Fe3O4/n-Si/Al heterojunction were depended on temperature, in which the barrier height increases while the ideality factor decreases with increasing temperature. According to calculations done by TE, the barrier height and ideality factor of Cr/GO-Fe3O4/n-Si/Al heterojunction device were found to be 0.26 eV and 2.46 eV at 100 K to 0.73 eV and 1.28 eV at 360 K. Additionally, the capacitance-voltage characteristics of the mentioned structure were analyzed at room temperature.

Introduction

Graphene is composed of a single layer of carbon atoms in two-dimensional hexagonal lattice. It has been found various applications in diverse areas since it shows the desired properties of the ideal materials for sensing applications rather than any other materials owing to its large surface area. In the electrical studies, graphene is a rising-star material as it is naturally compatible with thin film processing. Moreover, since graphene has low contact resistance (100 Ωμm) compared to the common metals like Ni, Cr and Ti, it enables to form rectifying junctions with several semiconductor materials such as Graphene/Si Schottky type devices [[1], [2], [3], [4]].

The properties of graphene make it an important material to be studied in future in the fields of photovoltaics [5,6], electronics [7], optoelectronics [8], photodetectors [9,10] and different types of sensors [11,12]. Therefore, the studies on Schottky contacts between graphene and different types of semiconductors have focused on the fabrication of devices that the electrical circuits of which includes graphene and other semiconductor materials [13]. Graphene oxide (GO) which is a graphene-based material has been discovered much earlier than graphene [14]. It has taken attentions of scientists due to high specific surface area, thermal properties, high flexibility and additional some properties leading it to be the two-dimensional support material for hosting metallic and bimetallic nanoparticles. GO has various functional groups such as, epoxy, hydroxyl, carboxylic and carbonyl groups. These functional groups enable the solubility and easy modification of GO material. π - π attractions between GO sheets lead different applications in material science [15]. Furthermore, GO is a hydrophilicity property and it is of a chemical stability [16], low cost due to being obtained from inexpensive graphite, abundant, soluble in water and mechanical strength [17]. Due to its excellent aqueous processability property, it can be used in biological applications [18].

Graphene oxide can be reduced to graphene-like layers by removing oxygen-containing groups. On the other hand, unlike graphene, graphene oxide contains structural defects and covalently bound defects and for this property, it is atomically rough [19]. This feature allows it to create heterojunction devices with various semiconductors. Furthermore, it is a candidate material for various application areas such as gas sensing [20], cancer therapy [21], energy storage [22], field effect transistor (FET) [23], solar cells, chemical sensors [24].

Graphene oxide can be synthesized via the Hummers method including the chemical oxidation and exfoliation of graphite flakes, which is schematically illustrated in Fig. 1[25].

In recent studies, scientists have given great importance to research on the half-metallic conductors to enhance the patterns and some electrical properties of the electronic devices. As known, only electrons having one spin direction are placed at the Fermi level of half metal substances. Namely, the spin of electrons in a half metal yields metallic behavior while the others are insulating [26]. For this purpose, they have utilized magnetite (Fe3O4) which is an applicable half-metallic conductor. This material has been started to use in engineering fields owing to its electrical properties such as strong spin polarization at Fermi level (EF), the high Curie temperature, the half-metallicity, the low electrical resistivity, and the stability. In this respect, Fe3O4 has received great attention of the scientists studying in the field of electronics since it has a high potential to be applied in many electronics devices owing to its featured properties. It has been reported that Fe3O4 can improve the performance of polymer electrolyte fuel cells (PEFCs) [27]. Till now, Fe3O4 has been fabricated on many substrates in a successful way such as on silicon (Si), platinum (Pt), aluminum oxide (Al2O3) and quartz [28].

On the other hand, as an interfacial layer, carbon-based polymers have had great field of applications especially in electrical or electronics devices technology. These polymers have been detected to be in a structure such as a mixed bond characteristic of graphite-like (sp2) and diamond like (sp3) [28]. In the synthesis processes of these materials, the studies dealing with structure, shape, composition and size of these materials have brought new paths of application in new potential areas [29].

Recently, the attempt of integrating GO or reduced GO (rGO) and Fe3O4 which are thin films, nanorods forms, into a single nanocomposite has been a center of focus in research studies because of combining the advantages of two component materials in one hand [[30], [31], [32]]. Furthermore, in addition to GO, graphene and Fe3O4 can be combined with different materials to work on triple composite structures. For example, Kumar et al. [33] have been developed rGO/PEDOT/Fe3O4 triple composite and they have studied the contribution of this composite structure to the green energy generation of air cathode microbial fuel cells.

The separation convenience of magnetic properties and the high surface area of heterogenous nature can be handled in the process of integrating magnetic nanoparticles into GO [34]. Besides of drug delivery, energy storage, contaminant removal; GO layers composed with Fe3O4 NPs have had potential of application in many different fields [35,36]. In this regard, we reported the synthesis of GO–Fe3O4 nanocomposites and the study of their device application in Au/GO–Fe3O4 nanocomposites/n-Si/Al configuration. Several electrical measurements of the devices were performed by evaluating the current-voltage (Isingle bondV) and capacitance voltage (Csingle bondV) characteristics at room temperature. In consequence, at lower and higher voltages, the ohmic and SCLC (space charge limited current) conduction mechanisms have been realized, respectively. Furthermore, it has been seen that the Isingle bondV measurements have been detected to be depend on the presence of the interface layer of the junction device [30]. This study is mainly about using GO-Fe3O4 nanocomposites as an alternative material to inorganic semiconductors in heterojunction devices possessing low cost, easy fabrication and etc. Furthermore, unlike many organic or inorganic materials, this study also offers the opportunity to work in a wide temperature zone without deterioration of GO-Fe3O4 nanocomposites. This implies that GO-Fe3O4 nanocomposites can be used in various electronic devices without any deterioration at low temperature ranges. In summary, one of the main elements of the study is that the GO-Fe3O4 layer creates a Silicon-compatible heterostructure and an improvement in device performance with respect to the metal/silicon Schottky device.

In this study, we have focused on a detailed analysis of the Isingle bondV and the Csingle bondV measurements of Cr/GO-Fe3O4/n-Si/Al junction device such that I-V measurements have been carried as a function of temperature performed between 100 K and 360 K in steps of 20 K. The transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis have been performed before forming the device. Temperature dependent device parameters such as barrier height, ideality factor and series resistance were calculated. Moreover, some basic parameters such as the ionized donor density, the barrier height, the Fermi energy level, the diffusion potential were studied by using the Csingle bondV measurements at 500 kHz frequency, at room temperature.

Section snippets

The preparation of n-Si wafer

The purity of n-Si wafer surface is an important for the successful fabrication of optical and electronics devices. This situation influences the device performance dramatically when there is any oxygen or other contaminations on the wafer surface. These processes were carried out in order to clean the surface of the n-Si. Firstly, n-Si wafer was cleaned with acetone and methanol for 15 min, respectively. Then, it was cleaned by using RCA1 cleaning procedure. RCA1 is a 6H2O:NH4OH:H2O2 (10 min,

The characterization of the GO–Fe3O4 nanocomposites

By using our well-established high-temperature thermal decomposition protocol [36], monodisperse Fe3O4 NPs were synthesized successfully and then assembled on GO nanosheets to yield GO-Fe3O4 nanocomposites by using liquid phase self-assembly method [29]. Since we reported the detailed structural analysis of GO-Fe3O4 nanocomposites elsewhere [29,36], only TEM, powder XRD and FTIR analysis of the GO-Fe3O4 nanocomposites were reported herein. As clearly seen by Fig. 3 that the representative TEM

Conclusion

In summary, the GO-Fe3O4 nanocomposites were synthesized by using a two-step procedure comprising the synthesis monodisperse Fe3O4 nanoparticles and their assembly onto the GO sheets. The characterization of this material was done by high quality techniques. Next, n-Si wafer was taken into the process of chemical cleaning. Then, the ohmic contact was handled by evaporating Al to the back of n-Si substrate before annealing. The bright side of n-Si was covered with GO-Fe3O4 film via the method of

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The financial support by “Atatürk University Scientific Research Project Coordination Council (Project No: FAD-2019-7025)” is gratefully acknowledged. The authors would like to thank Dr. Zakir Caldiran and Hatice Kacus for their technical support.

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