Characterization of ZnO Thin Films Prepared by Thermal Oxidation of Zn

Abstract

Zinc oxide thin films were prepared by thermal oxidation of zinc films at a temperature of 500°C for 2 h. The Zn films were deposited onto glass substrates by magnetron RF sputtering. The sputtering time varied from 2.5 min to 15 min. The physico-chemical characterization of the ZnO films was carried out depending on the Zn sputtering time. According to x-ray diffraction, ZnO films were polycrystalline and the Zn-ZnO phase transformation was direct. The mean transmittance of the ZnO films was around 80% and the band gap increased from 3.15 eV to 3.35 eV. Photoluminescence spectra show ultraviolet, visible, and infrared emission bands. The increase of the UV emission band was correlated with the improvement of the crystalline quality of the ZnO films. The concentration of native defects was found to decrease with increasing Zn sputtering time. The decrease of the electrical resistivity as a function of Zn sputtering time was linked to extrinsic hydrogen-related defects.

Insight on Photocatalytic and Photoinduced Antimicrobial Properties of ZnO Thin Films Deposited by HiPIMS through Thermal Oxidation

“…As the oxidation temperature increases, the crystallinity of the ZnO thin films can be enhanced, revealed by decreasing the full-width at half maximum (FWHM) of the principal diffraction peak [ 28 ]. This result is consistent with previous observations of ZnO films prepared by thermal oxidation of Zn [ 27 , 52 , 53 ].…”

“…The residual stress involves thermal and intrinsic components, while intrinsic stress could be triggered by the film deposition parameters such as temperature, applied power, and pressure [ 57 ]. The intrinsic stress could generate defects like twins, precipitates, disoriented grains, grain boundaries, and microcracks [ 27 ]. The various sputtering powers are responsible for such a morphological difference, which will be discussed later.…”

“…One approach to address this issue utilizes the post thermal oxidation method, which grows a thin layer of oxides on the surface of the substrate. Post thermal oxidation method generates ZnO films from the metallic Zn layers, which takes advantage of its simplicity and noticeable economy of the process [ 27 ].…”

“…Recently, several studies have reported developing ZnO films using thermal oxidation from sputtered Zn metal films [ 27 , 28 , 29 , 30 , 31 ]. The layered structure of the deposited Zn layers is changed from metal to Zn oxide phase by thermal oxidation, which involves the direct heating of a variety of metal substrates at a temperature in the range of 300–800 °C in the presence of air [ 32 ].…”

Zinc Oxide Defect Microstructure and Surface Chemistry Derived from Oxidation of Metallic Zinc: Thin‐Film Transistor and Sensor Behavior of ZnO Films and Rods

“…This type of texture formation in ZnO films obtained from oxidation of metallic zinc is not completely unprecedented, but such reportsa re rare. [29,30] Mostly,p referentialg rowth in the (002) direction [31,32] or random orientation of grains [33,34] have been reported. These differences are presumably attributablet ot he employed reaction conditions, as the texture can be controlled by the residual oxygen in the deposition process of the zinc metal and the presenceo fm oisture during the oxidation in air.T his is in accordancewith suggestions that polar surfaces in ZnO are stabilized by point defects or surface adsorbates.…”