Heteroepitaxy of PbS on porous silicon

Epitaxial PbS films were grown by molecular-beam epitaxy (MBE) on the surface of porous silicon (PS) formed on the silicon substrate of (111) orientation. The uniform PS layers 5 mu m thick were produced by electrochemical anodic treatment of n super(+)-silicon in HF solution. The structure of both PbS and buffer PS was studied by X-ray diffraction analysis as well as scanning electron microscopy. The PbS layer has been demonstrated to have a columnar structure at the early stages of growth, while a solid structure of the grown layer has been observed with increasing a thickness of the epitaxial layer up to 0.5-1.0 mu m. PbS epitaxial films grown on the substrates with the 2-5 mu m thick PS layers of 20-40% porosity were comparable with the films grown on the BaF sub(2) substrates.