PHASE-TRANSITION ON THE SI(111) SURFACE - A 1ST-ORDER PHASE-TRANSITION UNDER STRAIN

Experimental results from reflection high energy electron diffraction on the 7 x 7 <--> 1 x 1 phase transition at the (111) surface of silicon are presented. These results are consistent with a first order phase transition but with an important width in temperature. We develop simple arguments to show that a strain field applied by the volume on the surface can explain this broadening and also the phase coexistence.