Influence of Oxygen Gas Ratio on the Properties of Aluminum-Doped Zinc Oxide Films Prepared by Radio Frequency Magnetron Sputtering

Abstract

Aluminum-doped zinc oxide (AZO) thin films were deposited on glass and polyimide substrates using radio frequency magnetron sputtering. We investigated the effects of the oxygen gas ratio on the properties of the AZO films for Cu(In,Ga)Se2 thin-film solar cell applications. The structural and optical properties of the AZO thin films were measured using X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and UV-Visible-NIR spectrophotometry. The oxygen gas ratio played a crucial role in controlling the optical as well as electrical properties of the films. When oxygen gas was added into the film, the surface AZO thin films became smoother and the grains were enlarged while the preferred orientation changed from (0 0 2) to (1 0 0) plane direction of the hexagonal phase. An improvement in the transmittance of the AZO thin films was achieved with the addition of 2.5-% oxygen gas. The electrical resistivity was highly increased even for a small amount of the oxygen gas addition.

<span>Effect of limited oxygen gas flux on properties of Al-doped ZnO films</span>

“…The band gap slightly increases when the oxygen gas rates increase due to the shift of the absorption edge to shorter wavelengths (see figure 3a), which could be explained by Burstein -Moss effect (Cao et al, 2014). (1) The resistivity of n-type AZO thin films increases with increasing in oxygen flux, which is in good agreement with the previous work (M. Kim et al, 2016). Carrier concentration values are 1.72 ×10 19 cm -3 , 1.87 ×10 19 cm -3 , 2.19 ×10 19 cm -3 , and 2.13 ×10 19 cm -3 for samples 1, 2, 3 and 4, respectively.…”