Fabrication and characterization of reduced graphene oxide/silicon back-to-back schottky diode

Abstract

Graphene-based back-to-back Schottky diode (BBSD) is a simple device yet possesses promising attributes for applications such as chemical sensor and photodetector. Nevertheless, experimental work on graphene BBSD is relatively limited, where most of the works utilized graphene made from chemical vapor deposition and epitaxial growth. This work investigated the possibility of fabricating the BBSD using low-cost reduced graphene oxide (rGO) and simple fabrication techniques, namely vacuum filtration and chemical reduction via ascorbic acid. Understanding the capability and limitation of these fabrication techniques is important before they can be employed. Formation of graphene oxide (GO) thin film via vacuum filtration with different GO dispersion volume (50, 100, 150 and 200 ml) and concentration (0.4, 0.8, 1.0 ppm) were investigated. Thin films morphology and thickness were characterized using atomic force microscopy. The GO film thickness could be controlled from 30 to 160 nm by varying dispersion volume and concentration. As for reduction process, the correlation between reduction degree with reduction parameters, namely ascorbic acid concentration, duration and process sequence, were analyzed. The reduction degree was assessed by means of Raman spectroscopy and sheet resistance measurement. The lowest sheet resistance at 3.58 MΩ/sq was obtained for rGO film reduced before and after film transfer using 13.6 mg/ml ascorbic acid for 12 hours. Based on the result from vacuum filtration and chemical reduction processes, an rGO/silicon BBSD device was fabricated. The fabricated device was characterized by current-voltage measurement at different temperatures. A nonlinear curve was observed indicating the formation of double Schottky barrier at rGO/silicon junction. Barrier height, ideality factor and series resistance were extracted directly from the measured characteristics. The barrier height inhomogeneity was also assessed. The rGO/Si junction has average barrier height of 1.26 eV with standard deviation of 0.167 eV. In conclusion, the result from this work confirmed the feasibility of fabricating rGO BBSD using a low-cost graphene derivatives and fabrication technique. This is favorable towards mass production of graphene-based chemical sensor and photodetector.