Study on fluorination and hydrogenation in transparent conducting zinc oxide thin films#

Abstract

Fluorination and hydrogenation are known as two methods for enhancing crystalline structural and electrical properties of ZnO material. The ZnO thin films normally require a low resistivity and a high transmittance for using as high-performance transparent electrodes in optoelectronic applications. In this study, we report successful preparation of fluorinated and hydrogenated ZnO thin films (FZO and HFZO) by using d.c. magnetron sputtering technique. The hydrogenation was carried out by depositing the films in hydrogen plasma atmosphere, while a highly-sintered body of ZnO and ZnF₂ compound was employed as a sputtering target for the fluorination. The results showed that the strong improvements in carrier concentration, mobility and resistivity of the FZO and HFZO films as compared to the pure ZnO films. The carrier concentration increased to 2x10²ᴼ cmˉ³ which is mainly due to the hydrogenation. The effect combination of the fluorination and the hydrogenation was responsible for enhancing the mobility up to 43 cm₂ /Vs. These results gave rise to two-order reduction in resistivity, from 0.06 Ωcm (ZnO) to 7.5 x 10ˉ⁴ Ωcm (HFZO), which could be a good choice for thin-film electrode application. In addition, the crystalline structure and optical transmission of the films are also discussed.