Spin- And angle-resolved photoemission studies of the electronic structure of Si(110)" 16×2 " surfaces

The electronic structure of Si(110)"16×2" double-domain, single-domain, and 1×1 surfaces have been investigated using spin- and angle-resolved photoemission at sample temperatures of 77K and 300K. Angle-resolved photoemission was conducted using horizontally and vertically polarized 60eV and 80eV photons. Band-dispersion maps revealed four surface states (S1 to S4) which were assigned to silicon dangling bonds on the basis of measured binding energies and photoemission intensity changes between horizontal and vertical light polarizations. Three surface states (S1,S2, and S4), observed in the Si(110)"16×2" reconstruction, were assigned to Si adatoms and Si atoms present at the edges of the corrugated terrace structure. Only one of the four surface states, S3, was observed in both the Si(110)"16×2" and 1×1 band maps and consequently attributed to the pervasive Si zigzag chains that are components of both the Si(110)"16×2" and 1×1 surfaces. A state in the bulk-band region was attributed to an in-plane bond. All data were consistent with the adatom-buckling model of the Si(110)"16×2" surface. Whilst room temperature measurements of Py and Pz were statistically compatible with zero, Px measurements of the enantiomorphic A-type and B-type Si(110)"16×2" surfaces gave small average polarizations of around 1.5% that were opposite in sign. Further measurements at 77K on A-type Si(110)"16×2" surfaces gave a smaller value of +0.3%. An upper limit of ~1% may thus be taken for the longitudinal polarization.