Stress-induced splitting and shift of infrared absorption lines of platinum-hydrogen complexes in Si

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 1943.0cm^-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)°, the LVM of (Pt-H ₁)°, the symmetric-stretching mode of (Pt-H₂)°, LVMs of (Pt-H₃)^- and (Pt-H₃)°, and the LVM of an unidentified platinum-hydrogen complex, respectively. The peaks of (Pt-H₁)° and (Pt-H₂)° split into two components under (100) compressive stress, while those of (Pt-H₃)^- and (Pt-H₃)° did not split. We measured the stress dependence of the two split components of the (Pt-H₁)° peak. The low-wavenumber component shifted by -3.2cm^-1/GP&, 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-H ₁ 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 (110) symmetric axis with C_1h symmetry.