However, doped films can be made to have very
stable electrical and optical properties. The electrical
properties of as-deposited films appear to be highly
dependent upon the deposition methods, perhaps due
to different stoichiometries and oxygen chemisorption
on the surface of films and grain boundaries in polycrystalline
ZnO films. Although aluminum-doped ZnO
(ZnO:A1) films can be deposited using many methods,
the sol-gel process is simpler and less expensive and has the general advantage of producing high purity,
homogeneous films at relatively low temperatures.