Effects of uniaxial stress on local vibration of a platinum-hydrogen complex in silicon

We have studied stress-induced splitting and shift of an infrared (IR) absorption line at 1880.7 cm^-1 of the Pt-H₁ complex in Si by Fourier-transform IR (FT-IR) spectroscopy at 10K combined with the application of uniaxial compressive stress up to 0.4 GPa. The line was split into two and three components under 〈100〉 and 〈111〉 stresses with intensity ratios of low- to high-wavenumber components being 1:2 and 1:1:2, respectively. These results are consistent with C_1h symmetry in the piezospectroscopic theory of Kaplyanskii and the ESR results observed by Mchedlidze et al. Under 〈110〉 stress, however, the line was split only into two components, contradicting C_1h symmetry. Such inconsistency may be due to insufficient magnitude of stress. The split components were shifted linearly with increasing stress in the three directions. The isotope effects were observed for the Pt-H₁ complex. By replacing H with D, the IR line was shifted to 1358.5 cm^-1 and the 〈100〉 stress dependence of peak wavenumbers of two split components was weakened by a factor of 0.7.