Relativistic Effect on the Bistability of Bi {012} Nanofilms

Abstract

We perform fully-relativistic first-principles calculations on Bi{012}films which are stable when the film thickness is very small. We find that the 2ML free-standing film has bistability, i,e, the two top atoms are buckled in one geometry and they are nearly flat in the other geometry. The calculated amplitude of the buckling in the buckled structures is 0.17 Å whereas the amplitude is 0.41 Å when the spin-orbit interaction (SOI) is not included in the calculation. Furthermore, the bond lengths between the top and the second top atoms in the buckled structure are alternant when the SOI is included in the calculation. Therefore, the SOI has a significant effect on the geometry. The total energy difference between the two structures is less than 1 meV. Therefore, we expect that one of the two structures appears depending on circumstance such as the interaction between the substrate and the film. [DOI: 10.1380/ejssnt.2009.13]