Zinc-oxide thin film transistors (TFTs) with heavy metal cations such as indium zinc oxide (IZO)[1–3], zinc tin oxide (ZTO)[4–6], and indium gallium zinc oxide (IGZO)[7] offer an alternative to amorphous Si TFTs, due to their high mobility, high stability, and transparency. Among them, amorphous IGZO has been investigated for use as an active-channel layer since the first report on its use by Nomura et al.[8]. Recently, flexible and transparent TFTs were fabricated by depositing the IGZO channel layer on a polymer substrate by using pulsed laser deposition (PLD) and were found to exhibit moderate mobility [9]; however, their electrical properties need to be improved for practical applications. In ad-