Damping Oscillation of Buckled Dimers Induced by a Single Dimer Vacancy on Si(100) 2×1 Surface Near Critical Temperature

摘要

We have investigated the effects of vacancies on a phase transition by a Monte Carlo simulation using an Ising system, where the two states of a buckled dimer were regarded as spins up and down. First, we calculated the correlation length in the model, and subsequently, we introduced single-dimer vacancies to investigate their effect on the phase transition. As a result, not only the calculated specific heat became diffuse as a function of temperature, but also a dumping zigzag-chain type of an STM image was present in the vicinity of an isolated vacancy near the critical temperature T_c~(MC) (≈320 K) due to a strain field. The strain was considered to be a local next nearest neighbour antiferromagnetic one, where the strain energy (A) was deduced to be about 20 meV. We concluded that the frustrated STM image appeared as a result of the competition between the calculated critical temperature T_c~(MC) and the strain energy A.