Selective Homoepitaxial Growth of ZnO Layers on c(+)-Surface by Solvothermal Reaction in Water–Ethylene Glycol Solvent

Solvothermal deposition of ZnO layers on the c (±)-surfaces of ZnO single crystal substrates in a water-ethylene glycol solvent was investigated. Homoepitaxial growth of nanoparticulate layers was observed on the c (+)-surface. The manner of nanoparticle deposition on the c (+)-surface was similar to that of spherical particles precipitated in the solution, in that both grew through the oriented attachment of small particles during the early growth stage. The growth of the nanoparticulate film on the c (-)-surface was much slower than that on the c (+)-surface. After aging, the top surface of the film on the c (+)-surface transformed into a layer of pyramid-like particles so that the base of the pyramids was directed toward the surface. In contrast, randomly oriented pyramidal particles covered the c (-)-surface. Ostwald ripening through dissolution-recrystallization transformed the nanoparticles into pyramid-shaped particles in the latter stage when they were in contact with the solution. The faster growth on the c (+)-surface than on the c (-)-surface and the pyramidal shape of the particles with c (+)-basal plane deposited on the c (±)-surfaces after aging confirmed that the growth of the c (+)-plane was promoted, whereas the growth of {101̅0} and c (-)-planes was inhibited in this solution.