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Facet-Dependent Optical Properties of Semiconductor Nanocrystals
摘要： Recent observations of facet-dependent electrical conductivity and photocatalytic activity of various semiconductor crystals are presented. Then, the discovery of facet-dependent surface plasmon resonance absorption of metal–Cu2O core–shell nanocrystals with tunable sizes and shapes is discussed. The Cu2O shells also exhibit a facet-specific optical absorption feature. The facet-dependent electrical conductivity, photocatalytic activity, and optical properties are related phenomena, resulting from the presence of an ultrathin surface layer with different band structures and thus varying degrees of band bending for the {100}, {110}, and {111} faces of Cu2O to absorb light of somewhat different wavelengths. Recently, it is shown that the light absorption and photoluminescence properties of pure Cu2O cubes, octahedra, and rhombic dodecahedra also display size and facet effects because of their tunable band gaps. A modified band diagram of Cu2O can be constructed to incorporate these optical effects. Literature also provides examples of facet-dependent optical behaviors of semiconductor nanostructures, indicating that optical properties of nanoscale semiconductor materials are intrinsically facet-dependent. Some applications of semiconductor optical size and facet effects are considered.
关键词： surface band bending,semiconductors,facet-dependent properties,cuprous oxide,nanocrystals
更新于2025-09-19 17:15:36
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Depth-resolved electronic structure measurements by hard X-ray photoemission combined with X-ray total reflection: Direct probing of surface band bending of polar GaN
摘要： We have developed high-throughput depth-resolved electronic structure measurements using hard X-ray photoelectron spectroscopy (HAXPES) combined with X-ray total reflection (TR). By utilizing a steep change of the X-ray attenuation length around the TR condition, we controlled the effective inelastic mean-free-path of photoelectrons from >2 to >12 nm in HAXPES. We applied this method to probe the surface band bending of n-type polar GaN and found the different band bending behaviors in the Ga- and N-polar surfaces. This result is related to the surface contaminations and crystal quality near the surfaces of polar GaN.
关键词： hard X-ray photoelectron spectroscopy,surface band bending,depth-resolved electronic structure,polar GaN,X-ray total reflection
更新于2025-09-04 15:30:14