LI Shao-Juan1,3, HE Xin1, HAN De-Dong1, SUN Lei1, WANG Yi1, HAN Ru-Qi1 , CHAN Man-Sun2, ZHANG Sheng-Dong1,3**
1Institute of Microelectronics, Peking University, Beijing 100871 2Hong Kong University of Science and Technology, Hong Kong 3Shenzhen Graduate School, Peking University, Shenzhen 518055
LI Shao-Juan1,3, HE Xin1, HAN De-Dong1, SUN Lei1, WANG Yi1, HAN Ru-Qi1 , CHAN Man-Sun2, ZHANG Sheng-Dong1,3**
1Institute of Microelectronics, Peking University, Beijing 100871 2Hong Kong University of Science and Technology, Hong Kong 3Shenzhen Graduate School, Peking University, Shenzhen 518055
摘要The structural and electrical properties of ZnO films deposited by reactive radiofrequency sputtering with a metallic zinc target are systematically investigated. While the as-deposited ZnO film is in a poly-crystalline structure when the partial pressure of oxygen (pO2) is low, the grain size abruptly decreases to a few nanometers as pO2 increases to a critical value, and then becomes almost unchanged with a further increase in pO2. In addition, the resistivity of the ZnO films shows a non−monotonic dependence on pO2, including an abrupt transition of about seven orders of magnitude at the critical pO2. Thin−film transistors (TFTs) with the nanocrystalline ZnO films as channel layers have an on/off current ratio of more than 107, an off−current in the order of pA, a threshold voltage of about 4.5 V, and a carrier mobility of about 2 cm2/(V⋅s). The results show that radiofrequency sputtered ZnO with a zinc target is a promising candidate for high-performance ZnO TFTs.
Abstract：The structural and electrical properties of ZnO films deposited by reactive radiofrequency sputtering with a metallic zinc target are systematically investigated. While the as-deposited ZnO film is in a poly-crystalline structure when the partial pressure of oxygen (pO2) is low, the grain size abruptly decreases to a few nanometers as pO2 increases to a critical value, and then becomes almost unchanged with a further increase in pO2. In addition, the resistivity of the ZnO films shows a non−monotonic dependence on pO2, including an abrupt transition of about seven orders of magnitude at the critical pO2. Thin−film transistors (TFTs) with the nanocrystalline ZnO films as channel layers have an on/off current ratio of more than 107, an off−current in the order of pA, a threshold voltage of about 4.5 V, and a carrier mobility of about 2 cm2/(V⋅s). The results show that radiofrequency sputtered ZnO with a zinc target is a promising candidate for high-performance ZnO TFTs.
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2012, Vol. 29 
