Phase transitions on the (111) surface of diamond type semiconductors

The reconstruction and the phase transition are discussed on the (111) surfaces of Si and Ge by the use of the lattice gas model on a triangular net. A Monte Carlo simulation calculation is carried out of the lattice gas model. It is shown that the characteristic diffuse scattering of electrons in the (1x1) phase of Ge(111) can be reproduced by the model. Moreover, the underlying mechanism is discussed in terms of particle arrangements divided into irregular hexagon-like (2x2) domains which yield the diffuse patterns in the (1x1) phase. For the Si(111) surface, on the other hand, the calculation concludes the absence of stacking faults in the (1x1) state. The interrelation between the reconstructions of the surfaces is also discussed.