Ohmic-to-Schottky Modification of Zno-Metal Contact Modulated by Film Thickness

This work investigated the charge transport behavior at the interface between a Pt-Ir metal contact and transparent zinc oxide (ZnO) electrodes with one, four, and eight ZnO layers. Electrostatic force microscopy (EFM), Kelvin probe force microscopy (KPFM), and conducting atomic force microscopy (c-AFM) techniques were employed to explore the nanoscale surface electrical properties. The variation in thickness led to changes in the type of contact formed between metal and semiconductor, which went from ohmic to rectifier with the increase in the number of layers. The modulation in the type of contact formed was mainly due to the presence of grain boundaries (GB) during film formation. The influence of the thickness synthesis parameter on the optoelectronic and charge transport properties of conductive and transparent ZnO electrodes is demonstrated, and its importance in the formation of metal- semiconductor (M-S) contacts that make zinc oxide a versatile semiconductor.