Abstract
Temperature dependence of the second harmonic generation of the Si(111)-7×7 surface was measured in the temperature range from 550°C to 1100°C. For the first time Si(111)-7×7↔1×1 phase transition around 860°C was observed as an abrupt intensity change of the SH signal within 15 degrees using an optical technique. A hysteretic behavior with temperature difference of 2°C was observed in heating and cooling processes over the transition region. A gradual decrease of the SH intensity with temperature was also observed.