Grain and Grain Boundary Conduction Channels in Copper Iodide Thin Films

Abstract

Due to the textured nature of random in‐plane orientation of sputtered γ‐CuI (111) thin films, the crystalline grains and grain boundaries (GBs) influence charge carrier transport. Herein, current probe atomic force microscopy (cp‐AFM) measurements for differentiation and correlation of these morphological features and their contribution to electrical conductivity are presented, thus showing a clear difference between the conductive behavior of grains and GBs. A localized high and linearly voltage‐dependent current at the boundaries as well as a rectifying behavior between the platinum‐coated AFM tip and the grain surfaces is observed. Also, a different temporal evolution of voltage‐dependent conductivity is observed for grains and GBs. Further, the charge carrier transport through the surface vanishes with time. It is suspected that atmospheric oxygen causes these time‐dependent surface changes because accelerated degradation of the conductivity after oxygen plasma treatment is also measured.