The Influences of Thickness on the Optical and Electrical Properties of Dual-Ion-Beam Sputtering-Deposited Molybdenum-Doped Zinc Oxide Layer

The thickness of transparent conductive oxide (TCO) layer significantly affects not only the optical and electrical properties, but also its mechanical durability. To evaluate these influences on the molybdenum-doped zinc oxide layer deposited on a flexible polyethersulfone (PES) substrate by using a dual-ion-beam sputtering system, films with various thicknesses were prepared at a same condition and their optical and electrical performances have been compared. The results show that all the deposited films present a crystalline wurtzite structure, but the preferred orientation changes from (002) to (100) with increasing the film thickness. Thicker layer contains a relative higher carrier concentration, but the consequently accumulated higher internal stress might crack the film and retard the carrier mobility. The competition of these two opposite trends for carrier concentration and carrier mobility results in that the electrical resistivity of molybdenum-doped zinc oxide first decreases with the thickness but suddenly rises when a critical thickness is reached.