Transparent conducting Si-codoped Al-doped ZnO thin films prepared by magnetron sputtering using Al-doped ZnO powder targets containing SiC

Abstract

Transparent conducting Al-doped ZnO (AZO) thin films codoped with Si, or Si-codoped AZO (AZO:Si), were prepared by radio-frequency magnetron sputtering using a powder mixture of ZnO, Al2O3, and SiC as the target; the Si content (Si∕[Si+Zn] atomic ratio) was varied from 0to1at.%, but the Al content (Al∕[Al+Zn] atomic ratio) was held constant. To investigate the effect of carbon on the electrical properties of AZO:Si thin films prepared using the powder targets containing SiC, the authors also prepared thin films using a mixture of ZnO, Al2O3, and SiO2 or SiO powders as the target. They found that when AZO:Si thin films were deposited on glass substrates at about 200°C, both Al and Si doped into ZnO acted as effective donors and the atomic carbon originating from the sputtered target acted as a reducing agent. As a result, sufficient improvement was obtained in the spatial distribution of resistivity on the substrate surface in AZO:Si thin films prepared with a Si content (Si∕[Si+Zn] atomic ratio) of 0.75at.% using powder targets containing SiC. The improvement in resistivity distribution was mainly attributed to increases in both carrier concentration and Hall mobility at locations on the substrate corresponding to the target erosion region. In addition, the resistivity stability of AZO: Si thin films exposed to air for 30min at a high temperature was found to improve with increasing Si content.