Stress-Induced Splitting and Shift of Infrared Absorption Lines of Platinum–Hydrogen Complexes in Si

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We have studied the stress-induced splitting and shift of infrared (IR) absorption lines of platinum–hydrogen complexes in Si by Fourier-transform IR (FT-IR) spectroscopy at 10 K combined with the application of uniaxial stress. We observed several peaks at 1873.0, 1880.7, 1891.8, 1922.3, 1929.9, and 1943.0 cm-1. These peaks may be due to the previously observed local vibrational modes (LVMs) of various platinum–hydrogen complexes, that is, the antisymmetric-stretching mode of (Pt–H2)0, the LVM of (Pt–H1)0, the symmetric-stretching mode of (Pt–H2)0, LVMs of (Pt–H3)- and (Pt–H3)0, and the LVM of an unidentified platinum–hydrogen complex, respectively. The peaks of (Pt–H1)0 and (Pt–H2)0 split into two components under $\langle 100 \rangle$ compressive stress, while those of (Pt–H3)- and (Pt–H3)0 did not split. We measured the stress dependence of the two split components of the (Pt–H1)0 peak. The low-wavenumber component shifted by $-3.2$ cm-1/GPa, and the high-wavenumber component shifted by 4.2 cm-1/GPa. We show that these wavenumber shifts are equal to the piezospectroscopic tensor elements, A1 and A2, respectively. We propose a structural model of the Pt–H1 complex, where a hydrogen atom is bonded to one of four Si neighbors of the Pt atom in the {110} mirror plane perpendicular to the $\langle 110 \rangle$ symmetric axis with $C_{1h}$ symmetry.
2008-06-25