Room-temperature BTEX sensing characterization of nanostructured ZnO thin films

P Nagaraju,Y Vijayakumar,M V Ramana Reddy

doi:10.1080/21870764.2019.1579401

P Nagaraju, Y Vijayakumar + Show 1 more

Open Access

https://doi.org/10.1080/21870764.2019.1579401

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Abstract

ABSTRACTNanostructured zinc oxide (ZnO) thin films were deposited on glass substrates using various molar concentrations of zinc acetate dihydrate as the starting precursor at 400°C by the spray pyrolysis technique. The structural, morphological, and optical properties of the samples were investigated. X-ray diffraction studies showed thin films with a polycrystalline nature of the hexagonal wurtzite phase type. The preferred orientation was observed along the (002) direction. The crystallite size increased from 16.18nm to 20.42nm with increases in the molar concentration from 0.1M to 0.3M and then decreased further to 17.85nm at a molar concentration of 0.4M. SEM micrographs showed significant changes in the zinc oxide thin films with increases in the molar concentration of the precursor. Room-temperature Raman spectra confirmed typical electron-phonon coupling in the ZnO thin films. The optical band gap of the zinc oxide thin films was calculated using the Tauc plot. The sensitivity and selectivity of such toxic volatile organic vapors as benzene, toluene, ethylbenzene, and xylene (BTEX) were studied at room-temperature and reported.

Highlights

Zinc oxide (ZnO) thin films have attracted considerable attention in recent years due to their potential applications in the fields of catalysis, biology, and electronic and optoelectronic devices, such as transparent electrodes, thin film transistors [1], gas sensors [2], pressure sensors [3], microbicides [4], photocatalysis [5], blue and ultraviolet (UV) light emitters, room-temperature ultraviolet lasers [6], photovoltaic devices [7], and solar cell windows [8]
The present study examines the deposition of ZnO thin films by a spray pyrolysis technique at various precursor concentrations with optimized deposition parameters
The observed data for all the zinc oxide thin films sprayed at various precursor concentrations are in good agreement with data in a ZnO powder showing standard values obtained from JCPDS data card number 89–0510, which corresponds to a single-phase hexagonal wurtzite-type structure

Summary

Introduction

Zinc oxide (ZnO) thin films have attracted considerable attention in recent years due to their potential applications in the fields of catalysis, biology, and electronic and optoelectronic devices, such as transparent electrodes, thin film transistors [1], gas sensors [2], pressure sensors [3], microbicides [4], photocatalysis [5], blue and ultraviolet (UV) light emitters, room-temperature ultraviolet lasers [6], photovoltaic devices [7], and solar cell windows [8]. ZnO thin films have been deposited by such different methods as sputtering techniques [10,11,12], metal oxide chemical vapor deposition (MOCVD) [13], molecular beam epitaxy (MBE) [14], pulsed laser deposition [15], sol-gel processing [16,17], and spray pyrolysis [18] Among these methods, the spray pyrolysis method has attracted the especially great attention among researchers due to its simpler mechanism, low setup costs, and ability to spray large areas [19]. Volatile organic carbon compounds (VOCs) create significant impacts on the environment The presence of these gases in the atmosphere poses a serious threat to human beings and may lead to extreme health issues, and sometimes to death. Showing the influence of the precursor concentrations on their microstructures is systematically reported, and the films are exposed to different concentrations (in ppm) of benzene, toluene, ethylbenzene, and xylene to measure their sensitivity and selectivity as sensors

Experimental techniques

Structural characterization

Optical properties

Gas sensing properties

Conclusions