Controlling the extremely preferred orientation texturing of sol–gel derived ZnO thin films with sol and heat treatment parameters

In this article, material and process variables of sol–gel method are considered to investigate the texturing growth model of ZnO thin film in order to achieve ordinary, highly, and extremely preferred ZnO thin films. All the samples were fabricated by deposition of newly developed sol on conventional glass substrate via spin coating method and were further heat treated at various patterns. In sol variable, increasing the molar ratio of triethylamine to Zn increases preferred orientation along c-axis without using special heat treatment pattern. Various heat treatment parameters including drying and calcination are studied. The results demonstrate that drying at 300 °C is essential for achieving highly preferred ZnO thin film. In addition, calcination time, temperature, and repetition leads to more preferred sample to some extent. Furthermore, increasing the drying time at 300 °C causes significant increase of c-axis orientation and extremely preferential growth. In general, selection of an appropriate heat treatment pattern together with an accurate sol composition is necessary to achieve extremely preferred ZnO thin film with less energy conservation without using any special substrate. This is noteworthy that all the ZnO thin films are highly transparent in visible region and their band gap was around 3.3 eV.