Spectroscopic studies of the plasma for the preparation of Al-N co-doped ZnO films

Using optical emission spectroscopy measurements, the plasma formed for the preparation of zinc and aluminum co-doped ZnO films is studied. The O-2/N-2 mixed gas is excited by electron cyclotron resonance microwave discharge, generating an oxygen-nitrogen plasma. A zinc plume and an aluminum plume are induced by pulsed laser ablation of a zinc target and an aluminum target. The expansion of the plumes in the oxygen-nitrogen plasma enhances the excitation of the species of the oxygen-nitrogen plasma, while the ablated zinc and aluminum species are frequently excited at the same time, forming a highly reactive oxygen-nitrogen-zinc-aluminum plasma containing active oxygen- and nitrogen-related species excited from the O-2/N-2 gas and zinc and aluminum species ablated from the zinc and aluminum targets, as well as nitric oxide molecules produced in the plasma. The active oxygen species compose a reactive oxygen-containing gaseous environment for oxide formation, and the active zinc species react with the active oxygen species for ZnO film deposition, while the active nitrogen and aluminum species are in situ co-doped in the growing ZnO film. The optical properties of ZnO films are improved by zinc and aluminum co-doping including blue shifting of absorption edge, widening of band gap and preserving of high transparency. (C) 2017 Elsevier B.V. All rights reserved.