Dielectric discontinuity at structural boundaries in Si

摘要

The authors have explored optical dielectric constants, ε_∞, of ultrathin 3C(diamond)-Si(111) and 2H(wurtzite)-Si(0001) films using first-principles calculations in finite external electric fields. ε_∞ evaluated at the innermost region of the films approach values near their bulk dielectric constants at a thickness of only eight bilayers: 12.8 (3C) and 13.4 (2H). Furthermore, the authors have revealed that the spatial variation of ε_∞ near the stacking fault corresponding to the twin boundary for 3C-Si and that at the heteroboundary between 3C- and 2H-Si changes abruptly at the boundary for both cases. Such a locality in the variation of ε_∞ originates' from the local atomic arrangement at the boundary.