Dielectric discontinuity at structural boundaries in Si

Abstract

The authors have explored optical dielectric constants, ε ∞ , of ultrathin 3 C ( diamond ) - Si ( 111 ) and 2 H ( 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 ( 3 C ) and 13.4 ( 2 H ) . Furthermore, the authors have revealed that the spatial variation of ε ∞ near the stacking fault corresponding to the twin boundary for 3 C - Si and that at the heteroboundary between 3 C - and 2 H - 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.