  Natural silicon consists of three stable isotopes with atomic mass 28
(92.21%), 29 (4.70%) and 30 (3.09%). To present day, isotopic enrichment of Si
was used in electronics for two goals: (i) fabrication of substrates with high
level of doping and homogeneous distribution of impurities and (ii) for
fabrication of substrates with enhanced heat conduction which allows further
chips miniaturization. For the first purpose, enrichment of Si with Si-30 is
used, because after irradiation of a Si ingot by the thermal neutron flux in a
nuclear reactor, this isotope transmutes into a phosphorus atom which is a
donor impurity in Si. Enrichment of Si with Si-30 allows one to increase the
level of doping up to a factor of 30 with a high homogeneity of the impurity
distribution. The second purpose is achieved in Si highly enriched with isotope
Si-28, because mono-isotopic Si is characterized by enhanced thermal
conductivity. New potential of isotopically engineered Si comes to light
because of novel areas of fundamental and applied scientific activity connected
with spintronics and a semiconductor-based nuclear spin quantum computer where
electron and/or nuclear spins are the object of manipulation. In this case,
control of the abundance of nuclear spins is extremely important. Fortunately,
Si allows such a control, because only isotope Si-29 has a non-zero nuclear
spin. Therefore, enrichment or depletion of Si with isotope Si-29 will lead to
the creation of a material with a controlled concentration of nuclear spins.
Two examples of nano-devices for spintronics and quantum computation, based on
isotopically engineered silicon, are discussed.

Materials Science;Mesoscale and Nanoscale Physics