Hydrogen gas sensing properties of Pd/ZnO thin films grown on n-Si<100> substrates at room-temperature by thermal evaporation and sol-gel techniques: A comparative study

Jit, Satyabrata ; Yadav, Aniruddh Bahadur; Periasamy, C

Abstract

The present paper compares the room temperature hydrogen (H2) gas sensing properties of two Pd/nanocrystalline-ZnO thin film based Schottky contacts grown on n-type silicon (100) substrates by thermal evaporation and sol-gel techniques. The structural, surface and optical properties of the ZnO thin films under consideration are also presented. The Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) measurements have been carried out to study the surface morphologies and elementary compositions of the ZnO films,respectively. The X-ray diffraction (XRD) analysis shows that the ZnO thin films grown by both the methods are polycrystalline in nature with a hexagonal wurtzite structure. The optical band gaps of the films are estimated from the photoluminescence (PL) spectroscopy as 3.26 eV and 3.28 eV for thermal evaporation and sol-gel techniques, respectively. The current–voltage (I-V) measurements have been carried out to study the electrical and hydrogen (H2) sensing characteristics of Pd/ZnO Schottky contacts fabricated on the ZnO thin films grown by the two methods under consideration. Both the Pd/ZnO contacts under consideration are observed to have a good Schottky behaviour under dark condition and a high response to H2 gas with relatively short response and recovery times. Device fabricated by thermal evaporation shows better performance.

Keyword(s)

Nanocrystalline ZnO thin films, Palladium catalyst, H2 gas sensor, Schottky contacts, thermal evaporation, Sol-gel

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