Synthesis, properties, and applications of silicon nanocrystals

Silicon nanocrystals have been widely investigated for several years because of their many interesting properties and their potential use in several applications. This field has grown enormously after the observation of quantum confinement in porous silicon and remains an area of great interest for different reasons. Most importantly, silicon is already widely used in the semiconductor industry, is nontoxic at least in its bulk form, is the second most earth-abundant element in the crust, and is relatively cheap to process. A large number of groups have investigated silicon in the form of nanocrystals, and the authors intend to provide a comprehensive review of their contribution to the field. The author has decided to address first the synthesis and properties of silicon nanocrystals. Several different techniques, such as nucleation in substoichiometric thin films or gas-phase nucleation and growth in silane-containing nonthermal plasmas, have been proposed for the controlled synthesis of silicon nanoparticles. The author outlines the strengths and weaknesses of each approach and identify the research groups that have advanced each particular synthesis technique. The understanding of the properties of silicon nanocrystals has evolved as new synthetic approaches were developed, and for that reason the material properties are discussed together with its production approach. The use of silicon nanocrystals for the development of novel electronic devices, light emitting devices, photovoltaic cells, and for biorelated applications will be discussed. Waste heat recovery and energy storage applications are also discussed.