Photoluminescence (PL) properties of InN dots embedded in GaN were investigated. We observed a systematic blueshift in the emission energy as the average dot height was reduced. The widely size-tunable emission energy can be ascribed to the size quantization effect. Temperature-dependent PL measurements show that the emission peak energies of the dots are insensitive to temperature, as compared with that of bulk film, indicating the localization of carriers in the dots. A reduced quenching of the PL from the InN dots was also observed, implying superior emission properties for the embedded InN dot structures.

Structural and photoluminescence ͑PL͒ properties of InN dots grown on GaN by metal organic vapor phase epitaxy using the flow-rate modulation technique, and their dependence on growth conditions, were investigated. An ammonia ͑NH 3 ͒ background flow was intentionally supplied during indium deposition periods to control the kinetics of adatoms and hence the morphology of InN dots. Samples prepared under lower NH 3 background flows generally exhibit narrower and more intense PL signals peaked at lower emission energies. The authors point out that the NH 3 background flow is an important parameter that controls not only the nucleation process but also the emission property of InN dots.

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We observed that weakly and strongly rubbed polyvinyl-cinnamate surfaces align liquid crystal films perpendicular and parallel to the rubbing direction, respectively. Surface-specific sum-frequency vibrational spectroscopy was used to probe molecular orientations and alignments of the rubbed surfaces and provide a molecular-level understanding of the observation.