Investigation of WO3/ZnO thin-film heterojunction-based Schottky diodes for H2 gas sensing

Abstract

A comparative study of Schottky diode hydrogen gas sensors based on Pd/WO3/Si and Pd/WO3/ZnO/Si structure is presented in this work. Atomic force microscopy and X-ray photoelectron spectroscopy reveal that the WO3 sensing layer grown on ZnO has a rougher surface and better stoichiometric composition than the one grown on the Si substrate. Analysis of the I-V characteristics and dynamic response of the two sensors when exposed to different hydrogen concentrations and various temperatures indicate that with the addition of the ZnO layer, the diode can exhibit a larger voltage shift of 4.0 V, 10 times higher sensitivity, and shorter response and recovery times (105 s and 25 s, respectively) towards 10,000-ppm H2/air at 423 K. Study on the energy band diagram of the diode suggests that the barrier height is modulated by the WO3/ZnO heterojunction, which could be verified by the symmetrical sensing properties of the Pd/WO3/ZnO/Si gas sensor with respect to applied voltage.

The photovoltaic properties of a good rectifying Al/n-ZnO/p-Si/AL Schottky diode used in solar cell

“…Through the last decades, ZnO thin films and devices have been extensively investigated due to their potential applications in optoelectronic devices and photovoltaic cells.ZnO has attracted researchers in films and devices [1][2], it has intensively grown onto different substrates,like p-type silicon, InP, graphite, as thin films, Schottkybarrier diodes (SBD) and heterostructures (HS) [3][4][5].The ZnO devices based on ZnO have been fabricated by various methods like sputtering [6], spin coating and spray pyrolysis [7][8].The application of ZnO device are various, like gas sensors and solar cells [9][10].In the aim to prepare a photovoltaic device, we fabricate a Schottky diode based on a wide band gap semiconductor ZnO,Eg> 3 eV with a good rectifying behavior. The study's aim is to replace standard Schootky diode by those based on wide band gap oxide semiconductor.…”

Facile synthesis and gas sensing properties of In2O3–WO3 heterojunction nanofibers

“…Consequently, a simple method is needed to detect the concentration of acetone. In recent years, gas sensors based on metal oxide semiconductor nanomaterials, such as WO 3 [7][8][9], SnO 2 [10][11][12]40,41], ZnO [13,14], In 2 O 3 [15] and TiO 2 [16][17][18][19], have attracted much attention for the gas detection, due to its high response to the target gases and simplicity in preparation. WO 3 (Tungsten oxide) and In 2 O 3 (Indium oxide) are two kinds of great technologically important materials due to their excellent electronic, chemical and optical properties.…”

Porous silicon filled with Pd/WO3–ZnO composite thin film for enhanced H2 gas-sensing performance

“…56 In ambient air, the oxygen species adsorbed at the grain boundaries of WO 3 and ZnO and shield the WO 3 /ZnO heterojunctions such that the conducting electrons being trapped, and the composite layer become more resistive. 55,57 This results to create the barrier height at the WO 3 /ZnO heterojunction. Thereaer, the exposed H 2 gas molecules will reduce the adsorbed oxygen species on the surface.…”