Electrical and Structural Analyses of Solution-Processed Li-Doped ZnO Thin Film Transistors Exposed to Ambient Conditions

We report the electrical and structural features of various Li-doped ZnO thin-film transistors (TFTs) grown via a chemical solution process at low temperature. The time-dependent transfer curves for the 10 at. % Li-doped ZnO TFTs, including second-order lowered off-current magnitude, exhibited only a negative shift of $-1.07$ V for 25 days, compared with a $-21.83$ V negative shift of undoped ZnO TFTs. Secondary ion mass spectroscopy and X-ray photoelectron spectroscopy observations clearly demonstrated the structure of Li dopants and the reduction of oxygen vacancies after appropriate doping processes. Finally, the nature of improved stability in the Li-doped ZnO TFTs is described.