Solution of Ge(111)-(4×4)-Ag structure using direct methods applied to X-ray diffraction data

Abstract

A structure model for the Ge(111)-(4×4)-Ag surface is proposed. The model was derived by applying direct methods to surface X-ray diffraction data. It is a missing top layer reconstruction with six Ag atoms placed on Ge substitutional sites in one triangular subunit of the surface unit cell. A ring-like assembly containing nine Ge atoms is found in the other triangular subunit. The stability of the ring assembly may be due to Ge-Ge double bond formation. Trimers of Ge atoms, similar to the trimers found on the Ge(111)-(ǰ3×ǰ3)R30°-Ag surface, are placed in the corners of the unit cell.

High temperature growth of Ag phases on Ge(111)

“…3 showed the phase transition from [(4 Â 4) þ (3 Â 1)] ! This is consistent with previous studies of the structure of the (3 Â 1) phase, 2,8 with coverage close to 1/3 ML, and the (4 Â 4) phase, 3,4,9 with coverage of 0.375ML. and becomes brighter relative to the Ge surface.…”

“…1 Eight Ag phases have been reported for submonolayer coverages on Ge(111): (4 Â 4), (ͱ3 Â ͱ3)R30 , (3 Â 1), 2-4 (1 Â 1), (5 Â 1), 3 (12ͱ3 Â 12ͱ3)R30 , 5 (6 Â 6), 6,7 (ͱ39 Â ͱ39); 6 however, the latter four phases are observed under special preparation conditions and are not located on the proposed phase diagram. 3,4,9 The ͱ3 structure is referred to as a "honeycomb chained trimer" reconstruction with a Ag surface coverage of 1.00 ML, 3,7,10 similar to the ͱ3 reconstruction of Ag on Si(111). The (3 Â 1) structure is the "honeycomb chain channel" reconstruction with a Ag surface coverage of $1/3 monolayer (ML), similar to the Ag (3 Â 1) structure on Si(111).…”

Solution of the p(2×2) NiO() surface structure using direct methods

“…This problem has been solved for bulk X-ray diraction using an approach called direct methods. In the last few years, the direct methods approach has been successfully applied to twodimensional (2D) X-ray diraction data to solve surface structures [16,17], and more recently for 3D data [18]. This approach solves the phase problem by exploiting probability relationships between the amplitudes and the phases of the diracted beams.…”

Epitaxial Growth of Main Group Monoelemental 2D Materials

“…The growth of metals on semiconductors has been investigated intensively in the past decades as a means to develop the Schottky barrier formation. [ 114 ] Accordingly, the deposition of semiconductors on metal surfaces opens up an avenue for the fabrication of ME2DMs. However, most of them form compounds or surface alloys.…”