Influence of Annealing Temperature on the Properties of ZnGa2O4 Thin Films by Magnetron Sputtering

Abstract

Zinc gallate (ZnGa2O4) thin films were grown on sapphire (0001) substrate using radio frequency (RF) magnetron sputtering. After the thin film deposition process, the grown ZnGa2O4 was annealed at a temperature ranging from 500 to 900 °C at atmospheric conditions. The average crystallite size of the grown ZnGa2O4 thin films increased from 11.94 to 27.05 nm as the annealing temperature rose from 500 to 900 °C. Excess Ga released from ZnGa2O4 during thermal annealing treatment resulted in the appearance of a Ga2O3 phase. High-resolution transmission electron microscope image analysis revealed that the preferential crystallographic orientation of the well-arranged, quasi-single-crystalline ZnGa2O4 (111) plane lattice fringes were formed after the thermal annealing process. The effect of crystallite sizes and lattice strain on the width of the X-ray diffraction peak of the annealed ZnGa2O4 thin films were investigated using Williamson-Hall analysis. The results indicate that the crystalline quality of the deposited ZnGa2O4 thin film improved at higher annealing temperatures.

Zinc Gallium Oxide—A Review from Synthesis to Applications

“…The reason behind their lower luminescent intensity is the optical confinement of light due to planar interfaces [73]. Enhancing crystallinity of thin films then becomes an important issue and as a result of this issue, investigation of various parameters such as growth temperature, substrate species, oxygen pressure, and annealing temperature has taken place [74].…”

“…PLD exhibits significant advantages, such as the stoichiometry of deposited films close to that of the target, high deposition rate, low contamination level [71], precise arrival rates of atoms for compound films, and the ability to operate in high-pressure reactive gases [77]. In fact, RF magnetron sputtering has been the most successful among the various growth techniques for wide-area applications due to its easy controllability of the growth parameters, excellent packing density [74], strong adhesion, excellent film thickness uniformity, and relatively low running cost [78]. Polycrystalline or amorphous film structures are usually obtained by the RF magnetron sputtering method, which significantly affects the optoelectronic properties of the material [74].…”

“…In fact, RF magnetron sputtering has been the most successful among the various growth techniques for wide-area applications due to its easy controllability of the growth parameters, excellent packing density [74], strong adhesion, excellent film thickness uniformity, and relatively low running cost [78]. Polycrystalline or amorphous film structures are usually obtained by the RF magnetron sputtering method, which significantly affects the optoelectronic properties of the material [74].…”

“…Annealing is a popular method to enhance the crystallinity of ZnGa 2 O 4 thin films, although this method is accompanied by Zn depletion and oxygen deficiencies in the films, thus resulting in the deformation of the ZnGa 2 O 4 compound into its constituents (ZnO and Ga 2 O 3 ). Wang et al reported the influence of annealing temperature on the ZnGa 2 O 4 thin films on a c-plane sapphire substrate using RF magnetron sputtering [74]. The films were deposited at a substrate temperature of 400 • C and annealing temperature was increased from 500 to 900 • C in order to improve the crystallinity of the films.…”

Brillouin zone center phonon modes in ZnGa2O4

“…15 While ZGO has been grown and researched as a single crystal grown from flux [16][17][18] since the late 1960's, most previously published work focused on thin films, ceramics, and polycrystalline samples. 13,[19][20][21][22] Phonon modes are of basic interest for understanding carrier and heat transport, or photo excitation processes, for example. While some information on infrared (IR)-active as well as Raman-active modes was reported, a complete set of IR-active transverse (TO) and longitudinal optical (LO) phonon modes in ZGO is not available yet.…”