Mg-doped ZnO films prepared by chemical bath deposition

Abstract

A simple, low-temperature route for the chemical bath deposition of Mg-doped ZnO films, based on low-cost, abundant and non-toxic materials was developed. The film growth mechanism, the resulting morphology and texture were investigated in detail by scanning electron microscopy and X-ray diffraction measurements. It was found that substantial film growth is only possible in a narrow solution pH window due to the Zn(OH)2 supersaturation as driving force for the film deposition. Different amounts of Mg in the solution cause distinct (0001), (101 ¯ 0) or (101 ¯ 1) ZnO crystal textures. Speciation modelling helped to understand the solution chemistry and explain the occurrence of different textures by face-selective adsorption of Mg species onto specific ZnO faces. The amount of incorporated Mg into the ZnO lattice, determined by inductively coupled plasma atomic emission spectroscopy, was limited to 2.1 mol%. Optical band gaps, calculated from transmittance spectra, showed an increase with higher amounts of incorporated Mg and ranged between 3.41 and 3.55 eV.