Atomic structure of the Ag/Ge(111)-(3×3) surface: From scanning tunneling microscopy observation to theoretical study

Abstract

The atomic structure of the Ag/Ge(111)-(sq.rt.(3) x sq.rt.(3))R30 degrees surface is studied by scanning tunneling microscopy (STM) and the density functional theory (DFT) calculations. Our STM images have shown a structure which is different from the widely accepted honeycomb-chained-triangle (HCT) model before. The structure is similar to the inequivalent triangle (IET) model found for the Ag/Si(111)-(sq.rt.(3) x sq.rt(3))R30 degrees surface. This model proposed two types of silver triangles with different sizes in the unit cell, corresponding to the bright spots and the dark spots in the STM image. A distinguishable hexagonal pattern of the IET structure was well disclosed in the temperature range from 100 to 473 K in our STM studies for Ag/Ge(111)-(sq.rt.(3) x sq.rt.(3))R30 degrees. Furthermore, the result of the DFT calculations showed that the IET structure is 0.20 eV energetically more stable than the HCT model. Besides, the Ge triangles, which were not disclosed in earlier STM research, are found in this study.

Electronic and atomic structures of a3×3surface formed by a binary Sn/Ag overlayer on the Ge(111)c(2×8) surface: ARPES, LEED, and STM studies

“…This surface exhibits a honeycomb structure, as has been reported in the literature. 20 A similar honeycomb structure, but expanded and rotated by 30 • , is shown for the Sn/Ag/Ge(111) 3×3 surface by the empty-state STM image in Fig. 7(c).…”

“…The choice of Sn was, to some extent, triggered by the large number of studies of the Sn/Ge(111) √ 3× √ 3 and Sn/Ge(111) 3×3 surfaces that have appeared in the literature. Both the Ge(111)/Ag and Ge(111)/Sn systems are well studied, 17,[20][21][22] which provides a solid base of knowledge for the analysis of binary Sn/Ag overlayers.…”

Thermal evolution of Fe on Ge(1 1 1)–c(2 × 8) surface and the effect of (3×3)R30° Ag–Ge buffer layer

“…3)R30 • Ag-Ge buffer layer (Ag buffer layer), which confirmed as in-equivalent triangular (IET) [21] structures, is high thermal stability below 850 K [22,23]. Different Fe growth structures are expected because of the low interaction in the Fe-Ag phase diagram [24].…”

Structure of Co-2 × 2 nanoislands grown on Ag/Ge(111)-√3 × √3 surface studied by scanning tunneling microscopy

“…The buffering properties of the Ag/Ge(111)-√3 × √3 surface may be accounted for in terms of its unique atomic arrangement, which is currently well established based on the experimental [8-14] and theoretical work [13]. The approved structural models commonly propose that the √3 × √3 surface has a structure in which both the Ag atoms and the outermost Ge atoms are arranged in a triangular configuration.…”