Reactive Radiofrequency Sputtering-Deposited Nanocrystalline ZnO Thin-Film Transistors

• Published in: Chinese physics letters Vol. 29; no. 1; pp. 018501 - 1-018501-4
• Main Authors: LI, Shao-Juan, HE, Xin, HAN, De-Dong, SUN, Lei, WANG, Yi, HAN, Ru-Qi, CHAN, Man-Sun, ZHANG, Sheng-Dong
• Format: Journal Article
• Language: English
• Published: 01.01.2012
• Subjects: Grain size; Nanocrystals; Radiofrequency; Semiconductor devices; Thin film transistors; Transistors; Zinc; Zinc oxide
• ISSN: 0256-307X; 1741-3540
• DOI: 10.1088/0256-307X/92/1/018501

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 (pO sub(2)) is low, the grain size abruptly decreases to a few nanometers as pO sub(2) increases to a critical value, and then becomes almost unchanged with a further increase in pO sub(2). In addition, the resistivity of the ZnO films shows a non-monotonic dependence on pO sub(2), including an abrupt transition of about, seven orders of magnitude at the critical pO sub(2). Thin-film transistors ( TFTs) with the nanocrystalline ZnO films as channel layers have an on/off current ratio of more than 10 super(7) an off-current in the order of pA, a threshold voltage of about 4.5 V, and a carrier mobility of about 2 cm super(2)/(V times s). The results show that radiofreqnency sputtered ZnO with a zinc target is a promising candidate tor high-performance ZnO TFTs.