Preparation and characterization of indium zinc oxide thin film by sol-gel spin-coating technique

Transparent conducting oxide (TCO) films have been extensively researched for a variety of optoelectronic devices such as displays, solar cells, and low-e windows [1,2].Among the TCO films, ITO (Sn-doped indium oxide) is well known as the most commonly used materials with low resistivity and high optical transparency in the visible region.However, there is a growing demand for less expensivematerials (e.g., Zn O, In2O3 –Zn O , and SnO2) because of the high cost of ITO films. In particular, the In2O3 –ZnO system has attracted considerable interest. Moriga et al. studied the phase relations and physical properties of homologous compounds in a bulk In2O3 –ZnO system [3]. They identified nine homologous compounds of ZnkIn2Ok+3 (k =3,4,5,6,7,9,11, 13, and 15), which do not include ZnkIn2Ok+3 (k =1,2)that is unstable at the bulk phase. While In2O3 –ZnO thin films have been prepared by metal organic chemical vapor deposition [4], sputtering [5–7], and laser deposition [8], thin films prepared by sol–gel method are rare. The sol–gel method offers many advantages such as highly homogeneous thin films, large area coating, absence of the need for vacuum , low cost, and high flexibility. In this paper, by using this sol–gel technology, In2O3 –ZnO thin films were fabricated and their electrical and optical properties were investigated for several atomic ratios of Zn/(Zn+ In) (abbreviated as x). In addition, the effects of post-annealing condition on the properties of Zn2In2O5 (a homologous compound ZnkIn2Ok+3 where k =2) thin film were examined for oxidizing, inert, and reducing atmospheres