Paper TF-ThP26
Transparent Conducting Si-co-doped AZO Thin Films Prepared by Magnetron Sputtering Using AZO Powder Targets Containing SiC

Thursday, October 23, 2008, 6:00 pm, Room Hall D

Transparent conducting impurity-doped ZnO thin films are the best, and only practical, indium-free candidate suitable as a substitute for indium-tin-oxide (ITO) thin films used as transparent electrodes in liquid crystal displays (LCDs). However, they have not yet been used practically in LCD applications because of important obstacles such as a spatial distribution of resistivity and insufficient stability of resistivity in impurity-doped ZnO thin films prepared on low temperature substrates by conventional magnetron sputtering depositions. For the purpose of resolving these problems, we have demonstrated a new sputtering deposition technique that was developed to improve both the spatial distribution and the stability in resistivity; transparent conducting Al- and Si-co-doped ZnO (AZO:Si) thin films were prepared on glass substrates at approximately 200^oC by rf magnetron sputtering using a powder mixture of ZnO, Al₂O₃ and carborundum (SiC) as the target. The SiC content was varied, but the Al₂O₃ content was held constant. It was confirmed that the Al and Si contents (Al/(Al+Zn) and Si/(Si+Zn) atomic ratios) in the deposited thin films are approximately equal to those of the powder targets used, but carbon was not detected in all the deposited films. It was found that the spatial distribution of resistivity improved as the Si content of deposited films was increased up to approximately 0.75 at.%; the resistivity of deposited films decreased at the location on the substrate surface corresponding to near the erosion area on the target. This decrease in resistivity is attributed to increases of both carrier concentration and Hall mobility. Thus, the improvement of resistivity distribution obtained in the newly developed sputtering deposition technique may be due to a reducing effect originating from the carbon produced by sputtering the SiC containing AZO target during the film deposition. In addition, it was found that the stability of resistivity during long term tests at a high temperature in a highly moist environment of Si-co-doped AZO thin films is better than that of non-Si-co-doped AZO films prepared with the same thickness under the same deposition conditions.