Correlation between intrinsic defect and carrier transport in ZnO thin films by confocal Raman spectroscopy

An electric current through a transparent 80 nm ZnO thin film produces relevant changes on its Raman spectrum. The electrical current affects the vibrational modes of ZnO that are associated with intrinsic defects. A reversible Raman intensity decrease of the band centered at ∼578 cm−1 with the electrical current in the thin film is measured. The Raman peak decreases without a measurable energy shift, ruling out anharmornic contributions related to temperature increasing. The most probable mechanism is through a barrier height reduction with the applied electric field, producing a decrease of the charge at the crystallites interface or grain boundaries. The reported experiment is a direct proof of the significant role that intrinsic defects play on the electrical transport through ZnO thin films.