Alloys which contained C were studied by using self-consistent charge density-functional based tight-binding calculations. The causes of experimentally observed C-induced vibrational peaks near to 475, 607 and 810/cm were analyzed on the basis of theoretical calculations. The stabilities, vibrational frequencies, lattice relaxations and energy-gap variances of substitutional, interstitial single-C and di-C complexes in crystalline samples were calculated. All of the impurities introduced severe lattice relaxations of adjacent Si atoms. The peak near to 475/cm originated from the lattice relaxation of Si atoms, up to second-nearest neighbour, from C impurities. The peak near to 605/cm unexpectedly originated mainly from mid-bond interstitial C, whereas high-energy peaks near to 810/cm resulted from the formation of C complexes.

Structural and Vibrational Properties of Carbon Impurities in Crystalline Silicon. X.Y.Zhu, S.M.Lee, J.Y.Kim, Y.H.Lee, D.C.Chung, T.Frauenheim: Semiconductor Science and Technology, 2001, 16[5], R41-9