Abstract

We have investigated the temperature dependence of second-harmonic generation (SHG) from clean Si (111) 7×7 and Si (100) 2 × 1 surfaces. We find a strong influence of temperature on the second- order nonlinear susceptibility ${\text{χ}}_5^{{}^{(2)}}$ for both surfaces. In particular, changes in the SH signals by more than an order of magnitude have been observed over the temperature range of 200-1400 K. The data for the Si(111) 7 × 7 surface also display a sharp and pronounced jump at the temperature of the Si (111) 7 × 7 →1 ×1 order-disorder surface phase transition. By contrast, the optical properties of the bulk silicon change only very slightly (~1%) as a function of temperature. The present investigations add to the microscopic understanding of surface second-harmonic generation (SHG) and should permit future ultrafast measurements of surface heating and phase transitions of surface reconstruction.

© 1993 Optical Society of America