Room temperature near-field photoluminescence of zinc-blend and wurtzite ZnO structures

Near-field photoluminescence (PL) was measured from ZnO film, composed of nanocrystallites with zinc-blend (ZB) and wurtzite (W) structures, on a sapphire (0 0 0 1) substrate at room temperature (RT). The size of nanocrystallites was in the range of 30–50 nm. Using a fiber probe with aperture size of 80 nm, two near-field emission peaks attributed to one ZB and one W structures were observed. The difference in the emission energies was 0.10 eV close to the calculated bandgap difference between ZB andWstructures. The intensity of emission peak from ZB structure with lower energy was stronger than that from W structure, which is supposed to be resulted from the quenched excitonic effect of W structure