Temperature Dependence of Electrical Conductivity and Variable Hopping Range Mechanism on Graphene Oxide Films

Rapid development of optoelectronic applications for optical-to-electrical conversion has increased the interest in graphene oxide (GO) material. Here, graphene oxide films (GOF) were used as source material in an infrared photodetector configuration and temperature dependence of the electrical conductivity was studied. GOF were prepared by double-thermal decomposition (DTD) method at 973 K, as fixed carbonization temperature (TCA), in a pyrolysis system, under a controlled nitrogen atmosphere, over quartz substrates. Graphene oxide films were mechanically supported in a photodetector configuration on bakelite substrates and electrically contacted with copper wires and high-purity silver paint. Vibrational characteristics were studied employing Raman spectroscopy and it was determined the typical graphene oxide bands. GOF were used to discuss the effect of temperature on the film’s electrical conductivity. Current-voltage (IV) curves were taken for several temperatures varying from 20 to 300 K and the electrical resistance values were obtained from 142.86 to 2.14 kΩ. The GOF electrical conductivity and bandgap energy (E g ) were calculated and it was found that when increasing temperature, the electrical conductivity increased from 30.33 to 2023.97 S/m, similar to a semiconductor material, and E g shows a nonlinear change from 0.33 to 0.12 eV, with the increasing temperature. Conduction mechanism was described mainly by 3D-variable range hopping. Aditionally, measurements of voltage and electrical resistance, as a function of wavelength were considered, for a spectral range between 1300 nm and 3000 nm. It was evidenced that as the wavelength becomes longer, a greater number of free electrons are generated, which contribute to the electrical current. The EQE was determined for this proposed photodetector prototype, obtaining a value of 40%, similar to those reported for commercial semiconductor photodetectors. This study provides a groundwork for further development of graphene oxide films with high conductivity in large-scale preparation.