An understanding of key factors affecting the fabrication of ZnO thin films using CBD Process

The nano structured ZnO thin films are currently attracting considerable attention due to their size dependent properties and further applications in opto-electronic devices, sensors, solar cells, lasers, QLEDs, biomedical field etc. Thin film chemical deposition techniques are of special interest being relatively simple and convenient for large area deposition. Better grain structure with improved orientation of crystallites may be achieved by controlling the rate of reaction. Out of Chemical deposition techniques chemical bath deposition (CBD) is an inexpensive and energy efficient technique, as it does not require any high voltage equipment, works at low temperature and is widely used for deposition of various good quality metal chalcogenide thin films on a variety of substrates. In this article the basic principle underlying this process and film deposition mechanism has been described in detail. The effect of the factors affecting the ZnO film growth and morphology of the crystallites e.g. pH of the bath, nature and concentration of the precursors, effect of counter ion, nature and concentration of the complexing agent, thermal annealing, temperature of the bath, material of substrate and growth time has been analyzed. Various methods of seed layer deposition along with their benefits have been discussed at length.