Anionic Precursors, cat ionic precursors and a complexing agent are needed for a controlled synthesis of a thin film. In CBD they are taken together and subjected to thermal energy by some means to release the respective ions to favour the reaction. In Silar the precursor solutions are seperately kept in different beakers and ions are adsorbed on to substrate seperately and made to react. In modified SILAR both precursor solutions are kept in a single beaker, adsorbed simultaneously and made to react. In solgel a gelating agent is added to the precursor solutions and transferred to a substrate by spin or any means and collected by seperating the gel. For ZnO, films Zinc sulphate, Zinc Chloride, Zinc Nitrate or zinc acetate may be cationic precursor. For combustion involved synthesis methods nitrate may be prefered. All the best