RF-sputtering of doped zinc oxides thin films, the effect of low substrate heating deposition

Abstract

Zinc Oxide (ZnO) has been studied since 1930’s as a candidate for the electronic applications, as it possesses a wide bandgap of 3.4 eV. While in the last 3 decades the technology of thin films were more interested in Doped zinc oxide (ZnO) for their promising potential for many applications including thin film transistors (TFTs), transparent conductive electrodes (TCEs), and thin-film photovoltaic solar cells. Mainly Indium doped and Gallium doped-zinc-oxide (IZO), (GZO) and (IGZO) thin films have drawn researchers’ attention due to their remarkable electrical, optical properties, making them good candidate for the next generation flexible optoelectronic applications. This thesis work studies the effect of deposition parameters on the crystallinity and optical properties of the thin films. In addition, the chemical composition, electrical and morphological properties of the thin films were studied in a comparative form between room temperature (RT)-grown thin films and those gown with substrate heating at 200 °C. First, a series of doped ZnO thin films were deposited by radio frequency RF-sputtering at (RT), as a function of pressure, plasma power, and argon (Ar) flow. Then a chosen deposition recipe was tested with substrate heating. Well-adhered, uniform, smooth and highly transparent films were observed. Although Literature has shown that IZO thin films exhibit amorphous nature at RT-deposition, in this work it was observed that IZO thin films exhibits crystalline nature at RT. Results indicated that low substrate heating has affected both of IZO and GZO more than it has to IGZO Thin films. The low heat effect was more effective on the crystallinity and optical characteristics of these thin films more than its effect on their other characteristics, as it will be demonstrated as we go over each characteristic. Thicker films of (~1m) were grown in order to evaluate the mechanical properties, including film hardness (H) and Young’s Modulus (E).