ZnO thin-film transistors (ZnO-TFTs) on flexible substrates with SiO
2/TiO
2 buffer layers were fabricated at room temperature process. A SiO
2 layer of 200nm as a bottom oxide buffer was grown on PEN plastic substrates by an electron beam deposition. A 50nm TiO
2 buffer layer and a 40nm ZnO film were grown by a pulsed laser deposition (PLD) in continuously at room temperature. The TiO
2 thin layer between the ZnO thin film and the SiO
2 buffer layer provided a better adhesion, and demonstrated absence of in-plane disoriented grains without cracks. Top-gate type ZnO-TFTs were fabricated using the SiO
2/TiO
2 buffer layer, a transconductance,
gm of 1.7mS/mm, a drain current on/off ratio of 2.4 × 10
6 and a threshold voltage
VTH of -1.1V were obtained for a gate length
LG of 2μm. When compared with a SiO
2 buffer layer, a threshold voltage shift was about 1V in a positive direction, a higher voltage operation
VDS of 5V and a gate leakage current
IG of a few pA were obtained from a SiO
2/TiO
2 buffer layer ZnO-TFT. Furthermore, the ZnO-TFT was measured with bent to a curvature radius of 8.5mm. The
I-V characteristics were therefore not changed drastically by bending and after returning. In order to improve the
gm, the bottom-gate type ZnO-TFTs were also fabricated. The
gm of 12.5mS/mm was obtained at gate length
LG of 20μm. A transconductance,
gm was improved by applying the bottom-gate type TFT, that is the
gm became larger about 10times than that of the top-gate type TFT. From results of the bending experiments at curvature radius of 10mm, 20mm and 30mm. it was confirmed that the characteristics were not changed despite the bending and after returning for a short gate length devices.
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