Excited state properties of Si quantum dots

Silicon is the cornerstone of the semiconductor industry. In the nanoscale, the surface gains considerable significance due to the large surface to volume ratio. Recent theoretical advances in the investigation of the excited state properties of silicon quantum dots (QDs) are reviewed in this article. The origin of optical properties in silicon QDs is attributed to the tetrahedral crystalline structure in the Si nanostructures. Consequently, passivating the surfaces of these Si nanostructures by a suitable species turns out to be the most effective avenue for the retention of their tetrahedral structural symmetry and in turn their photoluminescence (PL) properties. The passivating agent and the extent of surface passivation need to be chosen very judiciously for the purpose of realizing the practical applications of the dots. Structural relaxation in the excited state induces Stokes shift, which varies with the particle size, the degree of surface passivation, and the nature of the passivating species. Stokes shift needs to be minimized for maximizing the PL efficiency of the QDs. All these intermingled issues are briefly addressed in the article. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.