Cooling rate determination of Si samples in a radiative quench and observation of an apparent temperature shift of the 1 × 1 – 7 × 7 surface phase transition

A simple method of cooling rate determination of Si samples in a radiative quench is presented. The method relies on monitoring of the LEED pattern of the Si(111) sample during quench and exact determination of the onset of the 1x1-7x7 phase transition using a videorecord of the process. The temperature decrease is found to be essentially linear and the cooling rate is constant over the temperature range 1275-840 degrees C. In different experiments this rate was about 300, 500 and 1000 degrees C/s for 0.4, 0.2 and 0.085 mm thick samples, respectively. An apparent temperature shift of the 1x1-7x7 phase transition upon quenching is observed for the first time. Slow relaxation of surface adatom concentration is assumed to be responsible for this shift. (C) 1997 Elsevier Science B.V.