DC sputtered ZrO₂/Zn_(1−x)Sn_(x)O thin-film transistors and their property evaluation

A bottom gate staggered 30 nm Zn_(1−x)Sn_(x)O (x = 0.14) (TZO)-based thin-film transistors (TFTs) were fabricated using DC magnetron reactive sputtering method. Highly transparent 120 nm dc sputtered ZrO₂ was used as a gate dielectric. The oxygen flow rate was varied from 20 to 24% during channel layer (TZO) coating and its effect on structural, morphological, optical, chemical, and electrical parameters were systematically studied. A nano scale roughness was noticed by atomic force microscopy (AFM), and ultra-smooth nature in root mean square roughness (RMS) was observed with an increment in the oxygen flow ratio. The increase in the oxygen-related defects with increase in the oxygen flow ratio in channel layer was evident from X-ray photoelectron spectroscopy (XPS). The electrical characterization of gate dielectric was carried out for Al–ZrO₂–Al structure. The high capacitance density ~ 121.9 nF/cm² for 120 nm ZrO₂ was obtained from the capacitance–voltage (C–V) measurement. The fabricated TFTs operated in n-channel depletion mode and indicated pinch-off region at lower source–drain voltages. In addition, the transfer characteristics of TFTs confirmed I _on/I _off ratio of 10⁵, with a field effect mobility of 23 cm²/V.s. This low temperature processed TFT unlocks the possibility of use in the next generation foldable display technology.