Study of gallium doping and substrate temperature effects on structural, electrical and optical properties of ZnO semiconductor layers

Abstract

In the present study, zinc oxide doped gallium thin films (ZnO:Ga) at different percentage (0.0, 1.0, 3.0 and 5.0 at.%) were deposited on glass substrates by magnetron sputtering technique using nanocrystalline particles elaborated by sol-gel method. The effect of Ga concentration and the deposition temperature on the structural, electrical and optical properties of the ZnO:Ga thin films were investigated. In the first step, the nanoparticles were synthesized by sol-gel method using supercritical drying in ethyl alcohol. The structural properties studied by X-ray diffractometry indicates that Ga doped ZnO has a polycrystalline hexagonal wurtzite structure with a grain size of about 30 nm. The transmission electron microscopy images have shown that the synthesized GZO is a nanosized powder. Then, thin films were deposited onto glass substrates by rf-magnetron sputtering at various substrate temperatures. The as deposited films with a thickness of about 300 nm were polycrystalline with a hexagonal wurtzite structure and preferentially oriented in the (002) crystallographic direction. The crystallite size ranged from 25 to 33 nm, depending on the deposition temperature and Ga at.%. Under particular growth conditions, the investigation shows that the Zn 0.97 Ga 0.03 O sample presents the best properties for potential use in various optoelectronic applications, namely: a single wurtzite phase, low surface roughness (Ra * 5 nm), a high transparency of 90 % in the UV-Vis-NIR, a wide band gap of 3.65 eV and a resistivity of *2.20 9 10 -3 X cm.

Structural Characterization of ZnO Thin Films Deposited onto Silicon Substrates using Cathodic Magnetron Sputtering

“…The films have a thickness of a few micrometers and a well-defined crystal structure on the substrate surface (Figure 10.c). These findings suggest that the sputtering synthesis method used in this study is effective for producing high-quality ZnO thin films with good crystalline properties [27].…”