SCANNING TUNNELING MICROSCOPE INVESTIGATION OF CDTE SUBSTRATE SURFACES FOR MOLECULAR-BEAM EPITAXY

CdTe substrate surfaces used for molecular beam epitaxy (MBE) have been investigated by scanning tunneling microscope (STM). The surface roughness was determined after different surface preparation steps. Mechanically polished samples show a surface roughness of about 1000 angstrom, caused by the polishing powder. By chemo-mechanical polishing procedures it was possible to reduce the roughness to about 60 angstrom. Typical surface structures with lateral dimensions of up to 200 angstrom and vertical dimensions of 40 angstrom remained after etch-polishing. This roughness was unaffected by sample preheats up to 300-degrees-C, but increased significantly above a temperature of 350-degrees-C.