透明導電ZnO-SnO2薄膜的成長及物理特性

Abstract

本論文研究的是以反應性直流磁控濺鍍法在Al2O3 (0001)基板上成長ZnO-SnO2透明半導體薄膜，並藉由改變薄膜的成份探討其光電性質。從薄膜的結構分析為及成份分析看來，初步斷定其為SnO2摻雜Zn。當薄膜的Zn摻雜量最少時(2 at.%)，可得到最低的電阻率ρ= 3.73×10-2 Ω-cm、最高的載子濃度n = 1.26×1019 cm-3、及最大的遷移率μ= 13.3 cm2V-1S-1；隨著Zn摻雜量增加到33 at.%，電阻率升高到4.03×10-1 Ω-cm、；載子濃度降至3.24×1018 cm-3。在溫度300 oC、真空(10-6 torr)下退火，可以有效的改善薄膜電性。薄膜在可見光區範圍內，平均透光率在90%以上。由吸收光譜圖可以知道能隙值隨著提高Zn摻雜量而變大。由低溫光激螢光光譜可得知薄膜可以發光，為可見光範圍的藍綠光。

In this thesis, the electrical and optical properties of ZnO-SnO2 transparent conducting thin films fabricated on Al2O3 (0001) by reactive DC magnetron sputtering were studied by modulating the Zn/Sn ratio. The phase of these samples was preliminary deduced to be Zn doped SnO2 by the structural and compositional analyses. At the minimum Zn doping (2 at.%), an optimal condition of the minimum resistivity of 3.73×10-2 Ω-cm with the maximum carrier concentration of 1.26×1019 cm-3 and the maximum mobility of 13.3 cm2V-1s-1 was obtained. When the doping concentration of Zn was increased to 33 at.%, the resistivity increased to 4.03×10-1 Ω-cm and the carrier concentration decreased to 3.24×1018 cm-3. On the other hand, the electrical properties of films were enormously improved by annealing at 300oc with 10-5 torr vaccum. An average transmittance above 90% in the visible range was obtained. The absorption specta also showed that the optical band gap of the materials became larger as the Zn content increased. The low temperature photoluminescence showed that the films were radiative in the visible range.