Versatility of chemical spray pyrolysis technique

The chemical spray pyrolysis technique (SPT) has been, during last three decades, one of the major techniques to deposit a wide variety of materials in thin film form. The prime requisite for obtaining good quality thin film is the optimisation of preparative conditions viz. substrate temperature, spray rate, concentration of solution etc. However, in recent years an emphasis has been given to a variety of atomization techniques such as ultrasonic nebulisation, improved spray hydrolysis, corona spray pyrolysis, electrostatic spray pyrolysis and microprocessor based spray pyrolysis. This is the most critical parameter as it enables control over the size of the droplets and their distribution over the preheated substrates. The enhancement in deposition efficiency and improvement in quality of the thin films can be achieved with these atomization techniques. The detailed processes are discussed in this review. An extensive review of thin film materials prepared during the last 10 years is given to demonstrate the versatility of the chemical SPT The various conditions to obtain thin films of metal oxide, metallic spinel oxides, binary, ternary and quaternary chalcogenides and superconducting oxides are also given. The effects of precursor dopants, substrate temperature, post annealing treatments, solution concentration etc., on the physico-chemical properties of these films are given as well. It is observed that the properties of thin films depend very much on the preparative conditions. The properties of the thin film can be easily tailored by adjusting or optimising these conditions, which in rum are suitable for a particular application. (C) 1999 Elsevier Science S.A. All rights reserved.