Investigation on the doping dependence of solution-processed zinc tin oxide thin film and thin-film transistors

The effect of the tin (Sn) concentration in zinc tin oxide (ZTO) films fabricated using a spin-coating process and its effect on ZTO channel thin film transistors (TFT _s) with various Sn concentrations were examined. Spin-coated ZTO films with various Sn concentrations were nanocrystalline and had high transmittance (>85%) in the visible region. As the Sn concentration increased, the carrier concentration and resistivity of the nanocrystalline ZTO (nc-ZTO) films ranged from 9.6 × 10 ¹⁴ cm ^-3 to 2.2 × 10 ¹⁶ cm ^-3 and from 1.5 × 10 ³ Ω-cm to 1.6 × 10 ² Ω-cm, respectively. The nc-ZTO channel TFTs that were deposited as a function of Sn and Zn concentrations exhibited a subthreshold gate voltage swing (S) of 1.1-1.2 V decade ^-1, an on/off ratio of 10 ⁵-10 ⁶, a threshold voltage (V _th) of -0.8-1.7 V, and a μ _FE value of 2.4-2.6 cm ² V ^-1 s ^-1. The threshold voltage shift toward the negative gate bias as the Sn concentration in the nc-ZTO TFTs increased indicates the existence of sufficient charge carriers needed to form conductive channels.