Abstract

Silicon nanocrystals exhibit unique optical and electrical properties due to their quantum size and charging effects, respectively. In the 1990s, for the first time, it was observed that nanostructured silicon in the form of porous silicon emitted efficiently visible light even at room temperature. Later, it was also observed that silicon nanocrystals with sizes smaller than the Bohr radius of the exciton in bulk silicon could also emit visible light. These observations triggered enormous efforts by the scientific community to use silicon nanostructures for optoelectronic applications, as this material could be integrated in an all-silicon chip containing optoelectronic components. Beyond their applications in optoelectronics, silicon nanocrystals showed potential use in sensors, photonics, and solar cells. The most recent report on 100% internal quantum efficiency of light-emitting silicon nanocrystals has revived interest in silicon nanocrystals as an efficient light-emitting material that could replace the toxic Cd- and Pb-based quantum dots in many biological and medical applications. On the other end, the charging effects observed in silicon nanocrystals have already been exploited in embedded nonvolatile memories in microcontrollers. In this chapter, we give a brief historical account on this field, present methods of growing silicon nanocrystals, and review their optical and electrical properties as well as the prospects for their applications in electronics, sensors, photonics, photovoltaic devices, biology, and medicine.