High-Performance and Flexible Neodymium- Doped Oxide Semiconductor Thin-Film Transistors With Copper Alloy Bottom-Gate Electrode

In this letter, copper alloy Cu-0.3 wt.% Cr-0.2 wt.% Zr film was used as bottom-gate electrode for flexible neodymium-doped InZnO thin-film transistor (TFT) applications. The results showed that the sputtering power and annealing temperature of a Cu–Cr–Zr film on a polyimide (PI) substrate greatly affect the resistivity and the adhesion of the gate electrode. And the lowest resistivity as well as the best adhesion was obtained by increasing power and annealing temperature to 150 W and 350°, respectively, which was compatible with the optimum annealing temperature of Nd.IZO channel. Transmission electron microscopy showed the aggregation and migration of Cr and Zr in the Cu–Cr–Zr layer, which results in a high adhesion strength and conductivity. As a result, the Nd.IZO TFT with the Cu–Cr–Zr bottom-gate electrode was fabricated on the PI substrate and demonstrated a saturation mobility ( \mu _{\text {sat}} ) of 27.0 cm 2 / \text {V}\cdot \text {s} , an ON/OFF current ratio ( {I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}} ) of 10 7 , a threshold voltage (V th ) of −0.1 V, and a subthreshold swing of 0.28 V/decade (no significant deterioration after 10k times repetitive bending stress). Furthermore, it exhibited a good mechanical bending stability of only a \Delta \text{V}_{\text {th}} shift of −0.3/0.43 V after 10k times repetitive bending stress under negative/positive gate bias stress conditions for 5400 s. mymargin