Low-temperature aqueous solution processed fluorine-doped zinc tin oxide thin-film transistors
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Low-temperature aqueous solution processed fluorine-doped zinc tin oxide thin-film transistors Jun-Hyuck Jeon, Young Hwan Hwang, JungHo Jin and Byeong-Soo Bae, Laboratory of Optical Materials and Coating (LOMC), Department of Materials Science and Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Korea Address all correspondence to Byeong-Soo Bae at [email protected] (Received 18 October 2011; accepted 10 January 2012)
Abstract Novel fluorine-doped zinc tin oxide (ZTO:F) thin-film transistors (TFTs) have been fabricated using an aqueous solution process. Exploiting hydrolysis and condensation reactions in an aqueous solution process, organic-free ZTO:F thin films were fabricated at a low temperature of 250 °C. The fabricated TFT device shows a field-effect mobility of 2.85 cm2/V s, on-to-off current ratios exceeding 107, and sub-threshold swings of 0.83 V/dec. The ZTO:F TFT also displays high operational stability of ΔVth = 1.73 V despite incorporation of a large amount of fluorine and use of a low-temperature annealing process. This is attributed to effective passivation of oxygen vacancy diffusion by metal fluoride bonds at the ZTO:F channel/gate dielectric interface.
Amorphous metal oxide semiconductors have attracted much attention as candidates for the backplanes of active-matrix organic light-emitting diode displays owing to their high field-effect mobility.[1] To date, outstanding progress has been made in the area of solution processing for oxide semiconductors, [2–4] as researchers attempt to meet the requirements of low-cost fabrication and printed electronics. Recently, a highperformance InZnO semiconductor fabricated under 250 °C using metal alkoxide precursors was reported.[4] However, fabrication steps requiring anhydrous conditions are very expensive and complicated.[5] Recently, solution processed ZnSnO (ZTO) thin films have been investigated for low-cost fabrication of oxide thin-film transistors (TFTs). Amorphous ZTO semiconductor exhibits excellent semiconducting properties and enables low-cost fabrication without an indium composition.[6] The conventional solution process for producing ZTO semiconductors utilizes a non-aqueous solvent such as acetonitrile or 2-methoxyethanol and metal chloride precursors. However, non-aqueous solutions with chloride precursors have a high decomposition temperature of more than 400 °C in order to obtain good electronic characteristics and also effect of chlorine residue is vague.[7,8] In this study, we report a low-temperature-processed, novel fluorine-doped zinc tin oxide (ZTO:F) TFT using a simple aqueous solution process. The aqueous solution process utilizing rapid hydrolysis and condensation reactions enables the lowenergy kinetics of M-O-M network formation without any organic residues. In particular, we emphasize that the overall fabrication cost is cheap for several reasons: (i) the process uses an inexpensive solvent (water) and affordable metal precursors and (ii) all ZTO:F film fabrication steps including
stirring, spin coating,
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