The Effect of Doping on the Structure of Zinc Oxide Obtained by Atomic Layer Deposition

Abstract

Zinc oxide (ZnO) is an interesting inexpensive transparent conductive oxide for use as a transport layer in multilayer solar cells. We present the results of a study of the effect of aluminum doping on the structure of 50-65 nm thin films of zinc oxide obtained by atomic layer deposition (ALD) on different substrates (glass, sapphire with a-plane and c-plane orientations). Analysis of thin films by IR spectra and X-ray diffraction showed the effect of doping on the crystallographic texture of films grown by the ALD method by comparing substrates of simple glass, c-plane Al2O3 and a-plane Al2O3. We found that when doping zinc oxide, the orientation of the substrate plays a substantial role, which affects the mechanism of interaction of zinc oxide with a doping agent, leading to changes in the structure and properties of ZnO due to the interaction between ZnO molecules and water to form a Zn-O-H bond. Doping with aluminum leads to a strain stress, resulting in distortion of the structure and a decrease in the concentration of oxygen vacancies. This is turn facilitates the flow of water molecules into the interlayer space and an increase in the density of the positive charge on the metal cation, which leads to an increase in the coordination number, i.e. to an increase in the number of hydroxyl groups.