Scanning tunneling microscope investigation of the effects of CdTe substrate preparation on molecular beam epitaxially grown [formula omitted] layers

Abstract

Because of the small lattice mismatch, CdTe is used as a substrate materials for the molecular beam epitaxial (MBE) growth of CdTe and Hg 1−x Cd x Te . For investigations of its structural surface properties on a nanometer scale, which greatly influence homogeneous growth, a scanning tunneling microscope is well suited. The surface roughness was determined after different surface preparation steps. Mechanically polished samples show a surface roughness of about 1000 Å, caused by the polishing powder. By chemico-mechanical polishing it was possible to reduce roughness to about 60 Å. Typical surface structures with lateral dimensions of up to 200 Å and vertical dimensions of 40 Å remained after etch-polishing. Further, we studied the effect of substrate polishing on the roughness of the MBE grown layers and found a strong correlation between substrate and layer roughness even for thick layers ( > 1 μ m ). The dependence of the growth temperature on the roughness of n-type CdTe layers is under investigation and the first results are presented.