On the diamond-cubic to hexagonal phase transformation in silicon

An analysis of electron diffraction data from silicon wafers implanted with 80 keV As+ at high dose rates has shown the presence of a hexagonal phase of Si (a one-element wurtzite structure). The hexagonal silicon consists of small rod-like particles with an orientation relationship to the diamond-cubic (d.c.) silicon lattice given approximately by ⟨0001⟩hex|⟨110⟩d.c. and ⟨0110⟩hex|⟨001⟩d.c.. This hexagonal silicon may also be produced by indenting the wafer surfaces at about 500 to 600°C (Eremenko and Nikitenko 1972) which produces large platelets with {115}d.c. habit planes. A phase transformation scheme is proposed for the silicon dc to hexagonal transformation. It is argued that the transformation may be induced by a uniaxial compressive stress and therefore represents a stress-relief mechanism. A structure model of the dc-hexagonal interface is proposed which consists of five- to seven-membered atomic rings without dangling bonds. © 1981 U.S. Government.