Abstract
TFTs on flexible plastic foils have the potential to enable new applications like electronic skins or smart textiles. Due to the temperature sensitivity of plastic substrates, amorphous In-Ga-Zn-O (a-IGZO) is a promising semiconductor since it provides a carrier mobility ≥10 cm2/Vs when deposited at room temperature. Therefore, a-IGZO TFTs have significantly increased electrical performance compared to organic TFTs, but also suffer from a decreased bendability. Here, focused ion beam (FIB) images are used to identify the gate metal as the dominant factor for the formation of cracks in bent a-IGZO TFTs. Flexible a-IGZO TFTs using a high-k Al2O 3 gate dielectric and different gate contact materials (Cr, Pt, Ti, or Cu) exhibit a similar effective mobility μFE, threshold voltage VTH, and on-off current ratio of: ≈15 cm2/Vs, ≈1 V, and ≥109. Simultaneously, bending experiments confirmed that their bendability depends on the ductility of the gate material. These findings are used to identify Cu as suitable gate material, and to fabricate a-IGZO TFTs on free-standing plastic foil which can be operated at a bending radius of 1.7 mm (1.55% strain), whereas bending shifts μFE and VTH only by + 2%, and - 6 mV.