Comprehensive Study on Electrical and Hydrogen Gas Sensing Characteristics of Pt/ZnO Nanocrystalline Thin Film-Based Schottky Diodes Grown on n-Si Substrate Using RF Sputtering

This paper presents a comprehensive study on the electrical characteristics of Pt/ZnO thin film Schottky contacts fabricated on n-Si substrates by RF sputtering, and its application as a Hydrogen sensor. The basic structural, surface morphological, and optical properties of the ZnO thin film were also been explored. Pt/ZnO thin film junction was characterized using current-voltage (I-V) and capacitance-voltage (C-V) measurements at room temperature, exhibiting rectifying behavior with barrier height, ideality factor and series resistance of 0.71 eV (I-V) /0.996 eV(C-V), 2.5 and ~95 Ω respectively. The lack of congruence between the values of Schottky barrier heights calculated from I-V and C-V measurements is interpreted. Cheung's method and modified Norde's functions were employed along with the conventional thermionic emission model, to incorporate the impact of series resistance in the calculation of diode parameters. We unveiled, the Hydrogen sensing characteristics displayed by the Pt/ZnO thin film-based sensor to different concentrations (200-1000 ppm) of Hydrogen at 350 °C. The sensor has exhibited good recoverable transient characteristics under a series of Hydrogen exposure cycles with a maximum sensitivity of 57% at 1000 ppm of Hydrogen.