Characterization of Zinc Oxide Thin Film Gas Sensors Fabricated by Pulsed-Laser Deposition

Abstract

In this work, pulsed-laser deposition (PLD) technique was used to prepare pure ZnO thin films on glass substrates. All prepared films were polycrystalline with hexagonal structure. The grain size and surface roughness were found to increase with increasing number of laser pulses. Optical properties showed that the films have high transmission in the visible region (>80%), in addition to a decrease in the transmittance with increasing number of laser pulses. The energy gap value was nearly 3.25 eV for all films. Based on the grain size of the film, 400 pulses were selected to make a gas sensor from pure ZnO films. These films showed different responses for sensing NO₂ and H₂S gases at three different operating temperatures (100, 150, and 200°C). The pure ZnO film sensor showed a sensing sensitivity for NO₂ gas of 90.24% with a response time of 25.2 s at an operating temperature of 200°C, while the maximum sensitivity for H₂S gas was 22.89% with a response time of 12.6 s at an operating temperature of 150°C.