Structure determination of Si(001)-c(4x2) surfaces at 80 K and electron beam effect below 40 K studied by low-energy electron diffraction -: art. no. 241306

We have studied the structures of the Si(001)-c(4x2) surfaces using low-energy electron diffraction analysis at 80 K. The asymmetric dimer model was optimized, and obtained structural parameters were almost identical with those previously reported by theoretical calculations. We analyzed both n-type and p-type samples and obtained almost the same structural parameters. Using the same samples, we measured changes in the intensity of diffraction spots in a temperature range of 24-120 K. The intensities of the quarter-order spots decreased significantly below 40 K, as in the recent study [Matsumoto et al., Phys. Rev. Lett. 90, 106103 (2003) ]. However, we confirmed that the intensity changes below 40 K are caused by the incident electron beam. We observed clear c(4x2) patterns immediately after irradiation of electron beam at 24 K, and concluded that the phase transition at 40 K, which was proposed by Matsumoto et al, is improbable.