Electronic and atomic structures of a 3 x 3 surface formed by a binary Sn/Ag overlayer on the Ge(111)c(2 x 8) surface: ARPES, LEED, and STM studies

• Published in: Physical review. B, Condensed matter and materials physics Vol. 85; no. 20
• Main Authors: Sohail, Hafiz M, Osiecki, J R, Uhrberg, R I G
• Format: Journal Article
• Language: English
• Published: 15-05-2012
• Subjects: Approximation; Atomic structure; Band structure of solids; Banded structure; Bands; Electronics; Scanning tunneling microscopy; Silver; Tin
• ISSN: 1098-0121; 1550-235X

The electronic and atomic structures of a well-ordered 3 x 3 periodicity of a binary Sn/Ag overlayer on Ge(111) have been studied. The ordered binary overlayer was formed by depositing 0.75 monolayer of Sn on an Ag/Ge(111) [radical]3 x [radical]3 surface. Annealing at 330 [degrees]C resulted in a low-energy electron diffraction pattern that exhibited sharp spots. A detailed electronic structure investigation was performed by angle-resolved photoelectron spectroscopy. The Sn/Ag/Ge(111) 3 x 3 surface shows a rich band structure. There are seven bands which are positively identified as 3 x 3 surface bands, all within 1.5 eV below the Fermi level (E sub(F)). The upper two bands disperse across E sub(F) exhibiting steep almost linear dispersions down to a minimum energy of [approximate]0.40 eV below E sub(F) at the [Gamma] point ([approximate]0.30 eV at the K point). Constant energy contours have been mapped in the 3 x 3 surface Brillouin zone (SBZ) in order to study an intriguing split observed in the band structure related to the two upper bands. It turned out that the two upper bands are degenerate along the [Gamma] - K and M - K symmetry lines of the 3 x 3 SBZ but separated along [Gamma] - M. Scanning tunneling microscopy images obtained at [approximate]40 K show essentially a hexagonal structure except for a honeycomb structure in a limited bias range imaging empty states. Core-level spectroscopy shows a narrow Sn 4d spectrum consistent with the high degree of structural order.