Transparent P-type Conductive Ternary Oxide Films Prepared by Reactive Sputtering Method

点击翻译按钮获取中文摘要

Cu-Al-O films were prepared on quarts substrates at 500〜700℃ by sputtering alternately the Cu and the Al targets on atomic-layer-scale under Ar-diluted O_2(5〜20%) gas atmosphere, and then annealed at 1050℃ under the nitrogen atmosphere. The [Cu]/[Al] ratio was controlled by changing Cu and Al deposition periods. Composition of as-deposited films corresponded to the slightly oxygen-rich region of the CuO-CuAl_2O_4-Al_2O_3 system. Films as-deposited at 500℃ had amorphous structure, while films as-deposited at 700℃ had CuAl_2O_4 and CuO phases. After thermal annealing, the film composition approached to the Cu_2O-CuAlO_2-Al_2O_3 system line, causing noticeable appearance of CuAlO_2 delafossite phase along with absences of the CuAl_2O_4 and CuO phases. Cu-rich and Al-rich annealed films had additionally Cu_2O phase and amorphous Al_2O_3 phase, respectively. All annealed films exhibited p-type conductivity. The annealed films with [Cu]/[Al]【approximately equal】1 had the absorption edge corresponding to the energy gap of CuAlO_2. These results indicate the change of Cu ion from di-valence to mono-valence through the annealing process, which results the preparation of transparent conductive films dominated by CuAlO_2. We also tried to irradiate the as-deposited films in order to crystallize the amorphous structure to CuAlO_2 delafossite structure by using a KrF laser in the power range of 10〜10^3 mJcm^<-2>. However, we observed no changes of the amorphous structure. At the power more than about 10^2 mJcm^<-2>, laser ablation of the films was observed.