Aging dynamics of solution-processed amorphous oxide semiconductor field effect transistors

This study determined the aging characteristics of solution-processed amorphous In?Ga?Zn oxide (a-IGZO) layers as amorphous oxide semiconductors (AOSs) for transparent, flexible thin-film transistor (TFT) applications. The work function of a-IGZOs upon exposure to air immediately after vacuum annealing was monitored using Kelvin probe force microscopy (KPFM). An increase was observed in the work function with time. Additionally, X-ray photoelectron spectroscopy combined with the KPFM results revealed two competing factors responsible for the aging characteristics: adsorption of oxygen molecules on the nanopore surfaces within the films, and the creation of defects, including oxygen vacancies and zinc interstitials. Although the former was reversible by alteration of ambient conditions, the latter was irreversible. On the basis of modified band theory, we proposed an operative mechanism for solution-processed AOS TFTs based on both the nature of porous amorphous structures and the aging dynamics. The perspectives reported here may be useful in designing and fabricating advanced, flexible AOS TFTs for device operations in stable ambient conditions.