Thermo-Electrical Properties of Composite Semiconductor Thin Films Composed of Nanocrystalline Graphene-Vanadium Oxides

Abstract

This paper presents an experimental comparative study involving the characterization of the thermo-electrical and structural properties of graphene-based vanadium oxide (graphene-VOx) composite thin films on insulating and conducting surfaces (i.e., fused quartz and acrylic resin-impregnated graphite) produced by a sol-gel process via dipping-pyrolysis. A combination of FE-SEM and XPS analyses revealed that the graphene-VOx composite thin films (coated onto fused quartz) exhibiting the microstructure of 2-graded nanowire arrays with a diameter of 40-80 nm were composed of graphene, a few residual oxygen-containing functional groups (i.e., C-O and C=O), and the VO2 Magnéli phase. The temperature-dependent electrical resistance measured on the as-deposited thin films clearly demonstrated that the graphene-VOx composite nanowire arrays thermally grown on fused quartz act as a semiconductor switch, with a transition temperature of 64.7 degrees C in the temperature range of -20 degrees C to 140 degrees C, resulting from the contributions of graphene and graphene oxides. In contrast, the graphene-VOx composite thin films deposited onto acrylic resin-impregnated graphite exhibit a superlinear semiconducting property of extremely low electrical resistance with negative temperature coefficients (i.e., approximately four orders of magnitude lower than that of the fused quartz), despite the similar microstructural and morphological characteristics. This difference is attributed to the synergistic effects of the paramagnetic metal feature of the tightly stacked nanowire arrays consisting of hexagonal V2O3 on the intrinsic electrical properties of the acrylic resin-impregnated graphite substrate, as revealed by FE-SEM, EDX, AFM, and XRD measurements. Although the thermo-sensitive electrical properties of the graphene-VOx composite thin films are very substrate specific, the applicability of graphene sheets can be considerably effective in the formation of highly planar arrays of VOx nanowires to enhance carrier transport.

Analysis of Entropy Generation in Mixed Convective Peristaltic Flow of Nanofluid

“…Table 1. Thermophysical parameters of water and nanoparticles [42,43]. The conditions are u ± β 1 S xy = 0, at y = ±η,…”

CNT suspended CuO+H2O nano fluid and energy analysis for the peristaltic flow in a permeable channel

“…Using above mentioned relation, properties of the nanofluid can be calculated and be applied to the governing equations. Thermal physical properties of water and nanoparticles are defined as [26][27][28][29][30] (see Table 1). …”

“…Further related literature can be viewed through Refs. [19][20][21][22][23][24][25][26][27][28][29][30].…”

Synthesis and Characterization of Graphene Oxide/Zinc Oxide (GO/ZnO) Nanocomposite and Its Utilization for Photocatalytic Degradation of Basic Fuchsin Dye

“…The energy gap depends on oxidization degree of graphene and species of oxygen containing groups. Preparation of graphene oxide (GO)/semiconductor and graphene/semiconductor composites have attracted much interest due to their superior properties for different application areas …”