Theoretical Scanning Tunneling Microscopy Images of the Ga-rich GaAs(001)-(4×2) Surface(STM-GaAs)

概要

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Total energy calculations have been performed for the Ga-rich GaAs(001)-(4×2) surface using first-principles plane-wave pseudopotential techniques. There are two distinctly different structural models proposed for the Ga-rich (4×2) surface. The Ga-model proposed by Biegelsen et al, consists of two Ga dimers on the top layer and another Ga dimer at the third layer, whereas the As-model by Skala et al. consists of two As dimers on the top layer and two Ga dimers in the second layer. Calculated results show that the As-model can be safely ruled out since the As-model is energetically unstable with respect to the Ga-model. The Ga-model, on the other hand, has a problem that there is apparent discrepancy between the STM image and the surface geometry of the Ga-model. It is found that the local density of states near the Fermi level are significantly affected by the existence of the third layer Ga dimers and that the Ga-dimer atoms on the top layer asymmetrically contribute to the STM image. The calculated charge distributions for the Ga-model can explain the observed STM image quite well.GaAs(001) surfaceSTM imageLDF calculation
東北大学の論文
1997-03-31