Formation of potential barriers at grain boundaries in multicomponent ZnO-based transparent thin films

The article discusses the reasons for the deterioration of the electrical characteristics of ZnO-based thin films in conditions of both high humidity and high ambient temperatures. Based on the standard damp heat test, in which thin samples subjected to temperature 85°C and relative humidity 85 % for 1000 h, it is shown that the stability of electrical performances of the transparent ZnO-based films may be increased with an increase in the temperature of their deposition, which, in turn, leads to the formation of denser compact films. It is shown that the porous structure formed in ZnO-based films, which leads to poor thermal stability, is due to the relatively low mobility of adatoms on the growing surface during film deposition at relatively low substrate temperatures. The analysis of the obtained data shows that the key factor determining both the composition and state of grain boundaries (GBs) in nanocrystalline ZnO-based films, as well as the formation of potential barriers at the GBs is the possible segregation of impurity materials at the GBs, which depends on the arrangement of impurity atoms with respect to Zn in the series of metal activity. The conditions for the amorphization of complex composite oxide structures are considered. © 2022, John Wiley and Sons Inc. All rights reserved.