Influences of growth conditions to morphology of ZnO thin films electrolessly deposited on Pd catalyst

ZnO films were electrolessly deposited in the aqueous solution of zinc nitrate and dimethylamine-borane (DMAB). ZnO was deposited on the Pd catalyst layer grown by sputtering on the quartz substrate. The influences of the growth conditions to the morphology of the ZnO films have been examined. Amorphous gel-like deposits were observed at 30 degrees C. Both amorphous gel and ZnO crystals were deposited at 40 degrees C. Above 55 degrees C, ZnO mono-particulate films with few particles being observed on them were obtained. The morphology of the ZnO depended on the concentration of Zn (0.01-0.5 mol center dot dm(-3)). In a low Zn concentration, spindle-shaped particles composed of fibers were deposited. In a high Zn concentration, platelet deposits of a few micrometers were observed. For deposition of hexagonal shape ZnO, the Zn concentration of 0.05 mol center dot dm(-3) was suited. The concentrations of DMAB (0.001-0.05 mol dm(-3)) did not influence the morphology of the deposits. At 55 degrees C, the deposition began just after soaking in the solution. Initially, the agglomerated particles of about 200 nm composed of small particles (10-30 nm) were deposited. According to the particle growth, the particles became hexagonal in shape. The hexagonal ZnO particles grew to micron sizes by the reaction for 4 h. At high reaction temperatures, the initial nucleation density was higher, and ZnO films of finer particles were obtained in a short period. After the catalyst layer was covered by ZnO, the growth rate became slow, but the growth continued due to the thermal decomposition of DMAB.