chapter  2
80 Pages

Structure and properties of silicon

Silicon (Si) is a chemical element, located at number 14 in the periodic table of elements. The outer electron shell structure is 3s23p2, so the silicon atoms are characterized by the state of sp3-hybridization of the orbitals and the manifestation of the oxidation state +4 or –4 in all chemical compounds except silicon monoxide SiO. Si atoms usually crystallize in the cubic structure of the diamond – the symmetry of the unit cell – a facecentred cubic F, the space group Fd 3 m (No. 227), the edge of the cell a = 0.54311 nm (Int. Tables, 2006). In the crystalline form Si has a slightly shiny dark gray color, density 2.33 g/cm3 and a melting point of 1415ºC. Since silicon has been used for a long time as the basic material of solidstate electronics, its properties in the crystalline and amorphous phases are very well studied, and the characteristics of these materials can be found in virtually all modern textbooks on solid state physics, where Si is considered as a reference sample, along with the classic diamond and semiconductors,

as well as in different directories of semiconductor materials. The properties of crystalline silicon are detailed, for example, in a large multi-author book, edited by R. Hull (Hull, 1999), dedicated only to this material, and the properties of amorphous silicon are described in detail in the book by Street (1991). Quite a lot of physical and chemical properties of silicon can be easily obtained, for example, on the Internet at the National Institute of Standards and Technology USA (http://srdata.nist.gov/gateway/, http://www.nist.gov/srd/), giving access to multiple databases. It should be said that the characteristics of silicon in the nanosized state are not so unambiguous and clear as the characteristics of the bulk crystals of Si, so they still continue to be studied and refined, which is reflected in numerous publications appearing in the last two decades in the periodic scientific literature, as well as in the continuously published monograph literature on this subject (see, e.g. Canham, 1997; Kumar, 2007; Khriachtchev, 2009; Pavessi & Turan, 2010).