Preparation and structural analysis of a PbSe-SnSe strained-layer superlattice

Publisher Website
Google Scholar
Abstract
A new superlattice composed of semiconducting PbSe and SnSe has been grown epitaxially on cleaved NaCl substrates by the vapor deposition method. The samples were characterized by x-ray diffraction and cross-sectional high-resolution transmission electron microscopy. Two materials have different crystal structures; PbSe has the cubic NaCl-type structure, whereas SnSe has the orthorhombic SnS-type structure, which is a distorted NaCl-type structure. The lattice mismatch between them is quite large, about 3%, and their growth planes have different symmetries. Therefore, this superlattice should not be classified as an ordinary superlattice like the GaAs-AlAs system, but as a so-called strained-layer superlattice. As a result of the structural analyses, it has been found that the samples have an ideal structure whose compositional modulation can be described by the step model with no mixed layers at the interface. In addition, we have observed a change of crystal symmetry in the PbSe layers: PbSe adopts the SnS-type structure when the thickness is less than about 30 Å, for coherency strain, but it relaxes back to the NaCl-type structure, with loss of the coherency, when the thickness is larger.

This publication has 19 references indexed in Scilit: