Semiconductor nanocrystals can be fabricated using a number of technologies, differing in the environment in which nanocrystals appear, growth conditions, size range, and size distribution, as well as physical and chemical stability and reliability. Nanocrystals can be developed in inorganic glasses and crystals, in liquid solutions and polymers, or on a crystalline surface. In this chapter we provide a brief overview of these techniques and give a synopsis of nanocrystals developed by various techniques.

Nanocrystals in inorganic matrices

Glass matrices: diffusion-controlled growth

Fabrication of nanocrystals embedded in a glass matrix by means of diffusion-controlled growth is based on commercial technologies developed for fabrication of color cut-off filters and photochromic glasses. Color cut-off filters produced by Corning (United States), Schott (Germany), Rubin (Russia), and Hoya (Japan) are just glasses containing nanometer-size crystallites of mixed II-VI compounds (CdSxSe1−x). Empirical methods of diffusion-controlled growth of semiconductor nanocrystals in a glass matrix have been known for decades or even centuries (in the case of color stained glasses). Commercial photochromic glasses developed in recent years contain nanocrystals of I-VII compounds (e.g., CuCl, CuBr, AgBr). Typically, silicate or borosilicate matrices are used with the absorption onset near 4 eV (about 300 nm), thus providing optical transmission of the semiconductor inclusions to be studied over the whole visible range.

Growth of crystallites results from the phase transition in a supersaturated viscous solution.