The bound polaron in a polar slab of the semiconductor

By using Green's function, the self-trapping energy of the bound polaron was studied in a polar slab, with respect to its relationship to the interaction between an electron with bulk longitudinal-optical (LO) and surface longitudinal-optical (SO) phonons. The self-trapping energy was derived as a function of slab thickness. Ee-phtr consisted of two parts, one was Ee-LOtr and the other was Ee-SOtr. Taking KCl as an example, Ee-LOtr increased with the increase of the slab thickness, but Ee-SOtr, Ee-phtr and λ all decreased with the increase of the slab thickness. The self-trapping energy was stablized to a low level when the slab thickness was above 5 nm, while when there was a Coulomb potential, it decreased; the reason was probably that the interactions were strengthened by the electrons and the phonons.