Fig. 1: Depletion layer engineering of metal oxide NCs via tuning of structural and electrical properties.
From: Control of electronic band profiles through depletion layer engineering in core–shell nanocrystals
The morphology of the nanocrystal (NC) is illustrated by a semi-circle with its extension \({{{R}}}\) in the abscissa (in nm) and the energy in the ordinate (in eV). In each panel, the left side of the sphere represents the flat-band potentials in the non-equilibrium condition, while the right side reports the band bending due to the Fermi level pinning (with the shaded region indicating the depletion width, \({{{W}}}\)). Band profiles were calculated by numerically solving the Poisson’s equation. a Tuning of surface state potentials (\({{{{E}}}}_{{{{S}}}}\)). Increasing the \({{{{E}}}}_{{{{S}}}}\) results in the expansion of the depletion width, \({{{W}}}\) (progressively from blue to red). b Impact of different materials on \({{{W}}}\) at fixed \({{{{E}}}}_{{{{S}}}}\). c Expansion of \({{{W}}}\) and double bending of the depletion layer in a core–shell structure of ITO-In2O3 with a core radius (\({{{{R}}}}_{{{{core}}}}\)) of 5.5 nm and varying shell thickness (\({{{{t}}}}_{{{{s}}}}\,{{{=}}}\,{{{0}}}{{{,}}}{{{1}}}{{{,}}}{{{2}}}{{{,}}}{{{3}}}{{{,}}}{{{4}}}\) nm, i.e., blue, light blue, orange, red and dark red, respectively). d Multiple shell system by combining an ITO core (\({{{{R}}}}_{{{{core}}}}\)= 5.5 nm) with a In2O3 and ZnO shell, with total radius \({{{R}}}\) = 9.5 nm. The band shows a complex profile with a triple bending (green curve). The gray curves illustrate the previously reported case of a uniform ITO NC (dark gray) and an ITO-In2O3 core–shell NC (light gray) with total radius \({{{R}}}\) = 9.5 nm for comparison.
