COOLING RATE DETERMINATION OF SI SAMPLES IN A RADIATIVE QUENCH AND OBSERVATION OF AN APPARENT TEMPERATURE SHIFT OF THE 1X1-7X7 SURFACE PHASE-TRANSITION

A simple method of cooling rate determination of Si samples in a radia tive 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 an d the cooling rate is constant over the temperature range 1275-840 deg rees 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 quenc hing is observed for the first time. Slow relaxation of surface adatom concentration is assumed to be responsible for this shift. (C) 1997 E lsevier Science B.V.