Optical characterization of ZnO thin films deposited by RF magnetron sputtering method

Abstract

This study investigated the process parameter effects on the structural and optical properties of ZnO thin film using radio frequency (RF) magnetron sputtering on amorphous glass substrates. The process parameters included RF power and working pressure. Results show that RF power was increased to promote the crystalline quality and decrease ZnO thin film defects. However, when the working pressure was increased to 3 Pa the ZnO thin film crystalline quality became worse. At a 200 W RF power and 1 Pa working pressure, the ZnO thin film with an optical band gap energy of 3.225 eV was obtained.ZnO thin films, RF magnetron sputtering, XRD, ultraviolet transmission spectrum ZnO is a kind of hexagonal wurtzite structure (hexagonal system, unit cell parameters: a=0.3249 nm, c= 0.52056 nm, c/a=1.602). ZnO is a novel material for II-VI wide band gap semiconductor material. It has a large room temperature band gap of 3.37 eV and a high binding energy of 60 meV which is much more higher than any other wide bandgap semiconductor materials (GaN: 25 meV, ZnSe: 22 meV). Its high exciton binding energy (60 meV at room temperature), which is much higher than room temperature heat energy (26 meV), will theoretically favor efficient UV emission processes at room temperature. Consequently, ZnO is a potential candidate for applications in optoelectronic device and receiving more and more important attention. ExperimentalThe ZnO thin films were deposited on amorphous glass substrates by RF magnetron sputtering using Zn (99.999%) target and varying working pressures (1, 1.5, 2, 3 Pa) [1] . The distance between sputter target and substrate was 90 mm. Ar was used as the sputtering gas and O 2 was used as the reactive gas. The thin films were investigated by X-ray diffraction (XRD) [2] and ultraviolet spectrophotometer [3] . XRD studiesThe Glancing Angle (3°) X-ray Diffraction was used to analyze the ZnO thin films [4] . Figure 1 shows the XRD pattern of different sputtering power ZnO films [5] by 1 Pa working pressure. XRD measurements showed that ZnO thin films deposited under different conditions all gave strong (0 0 2) diffraction peaks. Other peaks with much less intensities were observed, indicating that the films are oriented with their c axis perpendicular to the substrate plane.In this experimental, substrate could not be heated so RF power not only made the neutral gas in the vacuum chamber glow discharge, but also raised the temperature of the substrate and the vacuum chamber. As a result, the RF power improved the reaction between the Zn atoms and O atoms. Because of the RF power affected the sputter rate and the temperature of the substrate and vacuum chamber, both of the sputter rate and the temperature affected the thin films, so the power of the RF power affected the quality of the thin films. The less of the FWHM means the films are oriented with

Exploration of Wettability and Optical Aspects of ZnO Nano Thin Films Synthesized by Radio Frequency Magnetron Sputtering

“…The crystallinity was improved as deposition time was increased. Tang et al [14] reported evolution of only the (002) peak of ZnO at different deposition pressures of 1.0, 1.5, 2.0 and 3.0 Pa at constant RF power of 200 W. They observed that the intensity of the (002) peak for ZnO increased up to a pressure of 2.0 Pa. After a pressure of 3.0 Pa was reached, the intensity of the (002) peak decreased. We have also observed in our experiment that the intensity of various peaks of ZnO decreases when pressure is increased beyond 3.5 Pa.…”

Effect of sputtering pressure on the structure and properties of SiO 2 films prepared by magnetron sputtering

“…The film's structure and properties prepared with magnetron sputtering can be significantly affected by the sputtering pressure and other process parameters. Tang et al [12] prepared ZnO film with radio frequency (RF) magnetron sputtering and observed that the increase of sputtering pressure led to the grain size's increase, while its quality would decrease when the pressure was too high. Moon et al [13] investigated the effect of sputtering pressure on optical properties of aluminium‐doped ZnO thin film, and reported that the density and transmittance of the film increased with the decrease of pressure.…”

Characterization of Zinc oxide Nanostructures prepared by hydrothermal method with Antibacterial property

“…ZnO has wide band gap (3.37 eV), higher melting point (2248 k), large excitation binding energy (60 meV), ZnO NSs having hexagonal structure Wurtzite with lattice spacing constants (a = 0.325nm) and (c = 0.521 nm) [2] and has been widely used in many applications such as gas sensors, transparent conductive films, varistors, efficient photo catalysts, electrical and optical devices and antibacterial application [3][4][5][6]. Many different methods are used to synthesizes it; such as pulsed laser deposition (PLD) [7], sputtering [8], sol-gel [9], and metal organic chemical vapor deposition (MOCVD) [10] hydrothermal synthesis [11] etc. Among these methods, the hydrothermal method is more popular because of its simplicity, inexpensive, accuracy and repeatability.…”