Effect of annealing ambient on SnO2 thin film transistors

In this study, the effect of annealing ambient on SnO2 thin film transistors (TFTs) is presented. Phase pure SnO2 films have been deposited using solution processed spin coating technique with SnCl2 as the precursor material. The films are annealed at 500 degrees C for 1 h in different annealing ambient conditions with varying N-2:O-2 ratio. Top gate, bottom contact TFTs have been fabricated with SnO2 as the channel layer, silicon as the gate, silicon dioxide as the dielectric and gold as the contact material. XRD patterns reveal the amorphous nature of films. AFM image shows that the spin coated films are pin-hole free with extremely smooth surface morphology. PL and XPS measurements reveal that with increase in N-2% during annealing, the defects in the films increase. However, with increase in nitrogen concentration, the device performance improves, the threshold voltage shifts towards lower values and mobility increases, but very high N-2% is not suitable for device operation, a 70% N-2 + 30% O-2 annealing ambient is found to be suitable with devices showing saturation mobility of 0.23 cm(2)V(-1)s(-1) and threshold voltage of 6.8 V and on/off ratio of 10(6). (C) 2016 Elsevier B.V. All rights reserved.