Channel modification engineering by plasma processing in tin-oxide thin film transistor: Experimental results and first-principles calculation

In this paper, we investigated the effects of oxygen plasma treatment on tin oxide (SnO_x) thin film transistors (TFTs). By using oxygen plasma treatment on SnO_x active channel layer, excess oxygen was incorporated to the channel layer and converted oxygen-deficient SnO_x to oxygen-rich SnO_2-x, which in turn causes the device operation from p-type to n-type. Tuning the different exposure time of oxygen plasma, the optimal TFT device exhibits n-type properties with an on/off current ratio of 2.6 × 10⁴, a very high field-effect mobility of 89 cm² V^-1 s⁻¹, and a threshold voltage of −0.95 V. Furthermore, the effects of oxygen plasma treatment on band structure, density of states and electron density difference of the SnO_x channel layer were performed by the first-principles calculation using density functional theory. The results show that the oxygen plasma treatment approach has high potential for high-performance TFT applications.