Surface-dependent band structure variations and bond deviations of GaN

Abstract

Density functional theory (DFT) calculations on tunable number of GaN (0001) planes give invariant band structure, density of states (DOS) diagram, and band gap of GaN unit cell. Dissimilar band...

Aqueous Phase Photocatalytic Hydroxylation of Arylboronic Acids Using Polyhedral Cu2O Crystals

“…Interestingly, Ag 2 O crystals show an opposite facet-related photocatalytic activity trend . These facet-dependent observations can be understood to arise from the presence of a face-specific surface layer with slight variations in atom positions from bond length and direction deviations, leading to changes in the charge transfer ability across different crystal surfaces. − Initial X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis on Cu 2 O and SrTiO 3 polyhedra supports the existence of such slight lattice deviations between the surface and the crystal bulk. , In fact, the band structure of a crystal surface can be tuned through conjugated molecular functionalization, making Cu 2 O cubes possess an excellent photocatalytic activity. − Upon light absorption by semiconductor crystals to generate conduction band electrons and valence band holes, the electrons migrate to the crystal surface and reduce dissolved oxygen to form superoxide anion radicals (O 2 •– ), while holes oxidize water/hydroxide to give hydroxyl radicals ( • OH) . The radicals then decompose organic molecules.…”

Facet-dependent optical and electrical properties of SrTiO3 wafers

“…[7][8][9][10][11] Density functional theory calculations have suggested that there is a facet-specific surface layer with variations in bond length and bond direction causing the surface band structure changes. [12][13][14] Thus, different surfaces should have dissimilar barriers to charge transport to produce the electrical facet dependence. Surface trap states may also be related to the electrical facet effect.…”

Morphological evolution of cadmium oxide crystals showing color changes and facet-dependent conductivity behavior

“…[16][17][18][19][20] These facet-dependent behaviors, as revealed by density functional theory (DFT) calculations on Cu 2 O, Si, Ge, GaAs and GaN, result from the presence of a thin surface layer with dissimilar band structures for different surface planes. 5,[21][22][23][24][25] The band structure changes are linked to slight deviations in bond length and bond direction within the surface layer. [21][22][23][24][25] This surface layer naturally accounts for the observation of facet-related absorption and emission band shifts in various semiconductor nanocrystals including Cu 2 O, SrTiO 3 , CsPbX 3 and Ag 2 O.…”

“…5,[21][22][23][24][25] The band structure changes are linked to slight deviations in bond length and bond direction within the surface layer. [21][22][23][24][25] This surface layer naturally accounts for the observation of facet-related absorption and emission band shifts in various semiconductor nanocrystals including Cu 2 O, SrTiO 3 , CsPbX 3 and Ag 2 O. 2,19,[26][27][28][29] In addition to the optical facet effect, the absorption band, and hence band gap, can shift continuously from quantum nanostructures to very large particles.…”