Semiconductor nanocrystals possessing broadly size- and facet-dependent optical properties

Cu2O cubes, octahedra, and rhombic dodecahedra have been shown to exhibit continuous light absorption and emission band shifts with increasing particle sizes from 10 nm to sub-microcrystals. They also possess clear facet-dependent optical properties. Ag3PO4, Ag2O, SrTiO3, and CeO(2)crystals show similar optical size and facet effects. Thus, spectral shifts over a broad size range far beyond the quantum-size regime should be generally observable in many semiconductor materials. Facet-dependent optical properties of a semiconductor can be understood to arise from the presence of an ultrathin surface layer with subtle bond and orbital level variations for different crystal faces. Although these optical features seem unexpected, they should be the general behaviors of semiconductor crystals. As more examples of these optical effects are available, we will find that these intrinsic properties of semiconductors have been ignored in the past. Furthermore, if valence and conduction band positions are broadly tunable by particle size, the knowledge should have tremendous impacts on the applications of semiconductors, where band energies are important to efficient interfacial charge transfer.

Automated summary

Cu2O cubes, octahedra, and rhombic dodecahedra, as well as other semiconductor materials like Ag3PO4, Ag2O, SrTiO3, and CeO(2), exhibit continuous light absorption and emission band shifts with increasing particle sizes, indicating potential for broad spectral shifts beyond quantum-size regime. Facet-dependent optical properties of semiconductors are believed to originate from subtle variations in bond and orbital levels on different crystal faces, suggesting a previously overlooked intrinsic property of semiconductor materials that could have significant impacts on semiconductor applications.