SYNTHESIS OF ZNO SINGLE-CRYSTALS BY THE FLUX METHOD

Zinc oxide (ZnO) single crystals have been grown at temperatures ranging from 450-900-degrees-C and for 1-12 h, using hydrous KOH and NaOH melts as fluxes. For a KOH flux, brown ZnO single crystals with diameter 0.5 mm x 7.5 mm were grown under conditions of 500-degrees-C for 20 h and white crystals of diameter 0.5 mm x 7 mm were grown at 800-degrees-C for 20 h, using a small crucible (average 50 ml). When a large crucible (average 400 ml) was used, ZnO single crystals with diameter 0.5 mm x 8 mm were formed at 900-degrees-C for 30 h. When using a KOH + NaOH (1 : 1) flux, light-brown and long crystals with diameter 1.0 mm x 18 mm could be grown. The grown ZnO single crystals were bounded with only both p- and m-faces. It seems that crystal qualities were good under conditions of 900-degrees-C for 30 h. The following mechanisms of dissociation and formation of ZnO single crystal from KOH (or NaOH) + ZnO melt seemed to occur KOH(or NaOH) --> K+ (or Na+) + OH-ZnO + 2 OH- --> ZnO22- + H2O, ZnO22- --> ZnO + O2-.