Effects of cooling rate and oxygen partial pressure in flowing Ar on ultraviolet (UV) emission of In-doped ZnO nanodisks grown by carbothermal reduction at 1000 deg C were studied. The In doping favored the growth of ZnO nanodisks instead of ZnO nanowires. Air-cooled ZnO nanodisks showed a strong green emission, while furnace cooling in conjunction with introducing O_2, around 1.0 percent, into flowing Ar during growth significantly enhanced the growth and UV emission of ZnO nanodisks. The causes can be attributed to the reduction of oxygen vacancies and surface defects in ZnO nanodisks. However, higher oxygen partial pressure in flowing Ar resulted in a decrease in the Zn vapor and thus suppressed the growth and UV emission of ZnO nanodisks.
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