GALYUM KATKILI ÇİNKO OKSİT İNCE FİLMLERİN KARAKTERİZASYONU VE ÜRETİM PARAMETRELERİNİN İNCE FİLMLERE OLAN ETKİLERİNİN İNCELENMESİ

Abstract

Transparent conductive oxide (TCO) thin films are materials with low resistivity values as well as high optical transmittance. Thanks to these outstanding features, they pave the way for many high-tech applications such as optoelectronics, thin film transistors, solar cells, liquid crystal displays (LCD), touch screens and energy saving windows. Indium tin oxide (ITO), owing to its wide application area, different techniques of production, chemical stability, good electrical conductivity and high optical transparency, has become the most preferred TCO thin film material. Recently, even though its popularity among the TCO research society, alternative TCO thin films are being tried to be developed because of inadequate indium sources, its high cost and toxicity. With this motivation, studies on gallium (Ga) doped zinc oxide (ZnO) TCO thin films have gained importance from day by day due to its high optical transparency, good electrical conductivity, non-toxicity and low cost. Ga-doped ZnO thin films can be produced by many production techniques such as RF magnetron sputtering. In this method, deposition parameters directly influence the final characteristics of the thin films. Studies on this subject are mainly focused on investigating the effects of these deposition parameters such as RF power, Argon pressure during the process, distance between the target and the substrate, substrate temperature, deposition temperature and deposition rate on thin films and hence defining the optimal deposition parameters. In the scope of this thesis, Ga doped ZnO films deposited by RF magnetron sputtering technique by different RF power and Ar pressures are characterized. To understand the optical, electrical and structural properties of the thin films, atomic force microscope (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible spectrophotometry (UV-VIS), focused ion beam (FIB) and four-point probe characterization equipments are used. As a result of characterizations, thin film with an RF power of 230 W and Ar pressure of 0.4 Pa is found to have best characteristics for TCO applications. This Ga-doped ZnO film, with a deposition rate of 14.37 nm/min and 430 nm of film thickness, has optical transmittance of 83.2 % within the wavelength range of 400-800 nm. In addition, it is found to have an average of 120 grains with 32.5 (±18.8) nm crystallite size, 8.96 nm of surface roughness, 1.51×E-4 Ω.cm resistivity, 7.19×E21 cm-3 carrier concentration 5.72 cm2/V.s of Hall mobility. Atomic percentages of the elements of Zn, O and Ga in the film are found to be 49.54 %, 46.11 % and 4.35 %, respectively. In the light of this information obtained from the characterization results, the effect of RF power and Ar process pressure on the resulting thin film characteristics is well understood, and bridging over the production of better optimized high quality doped ZnO thin films is aimed.