Thermal effects in photoemission from Bi(1 1 1) films on Si(1 1 1)-(7 × 7)

An angle-resolved photoemission study of epitaxied Bi(1 1 1) film on Si(1 1 1)-(7 × 7) surface has been carried out at a temperature from 10 K to 210 K. The results show that there exists strong temperature dependence in the valence band of Bi(1 1 1) film. The variations in the spectral intensity and shape indicate the importance of phonon-assisted indirect transition in the photoemission process. The thermal sensitivity coefficients and effective Debye temperatures for main spectral peaks are determined from the experimental data.