Reflectance anisotropy from non-III–V systems: Si and SiGe growth on (001) Si and adsorbate-induced reconstruction of Cu(110)

Reflectance anisotropy (RA) data are presented for the study of two discrete systems - the dynamic growth of Si and SiGe on Si(001) and the formation of ordered overlayers on Cu(110). In the first of these studies first examples are presented of high quality RA oscillations and simultaneously recorded RHEED oscillations obtained during the growth of Si and SiGe on Si (001) by gas source MBE using disilane and germane at temperatures of 600 °C. RA measurements clearly demonstrate an enhancement in growth rate upon introduction of germane to the disilane flow. For both systems, the RA was found to oscillate at a period corresponding to bilayer growth which is explained in terms of a model based upon the changes in relative domain size and hence Si dimer concentration on the two orthogonal [110] azimuths. The RA data are also compared with variations in the total reflectance of the growing surfaces which is recorded simultaneously. In the second study it is demonstrated here that the RA technique may also be applied to the study of surface processes occurring at a metal single crystal surface. A marked RA response was observed from a Cu(110) single crystal under conditions where adsorption of O 2 , O 2 + formic acid, and benzoic acid results in a re-structuring of the surface as determined independently using LEED. Dynamic RA responses corresponding to (R 110 - R 001 )/R tot are correlated with exposure of the various adsorbates and the appearance of particular overlayer structures. It is suggested that the RA response observed comes from a quenching of an allowed surface transition of the clean Cu(110) surface by the electronic perturbation induced by the adsorbates. If correct, this explanation would add much weight to the currently held interpretation of RA data from III-V systems which invokes similar geometrically oriented surface state transitions. However, at present, the possibility of involvement of new adsorbate-induced surface states cannot be ruled out.