Scanning tunneling microscopy of Sr adsorption on the Si(100)-2×1 surface

Abstract

The Sr-induced ordered superstructures on the Si(100)-2×1 surface have been studied using ultrahigh vacuum scanning tunneling microscopy and low-energy electron diffraction (LEED) for metal coverages (θ) below one monolayer (ML). At very low coverages (θ≤0.01 ML) Sr atoms adsorb as isolated atoms or small clusters. At submonolayer coverages of ∼θ≥0.12 ML we have observed the alkali-earth metal chains, even at room temperature, that run perpendicular to the substrate dimer rows. It is found that the Sr rows form areas of (2×3) order for coverages θ about 1/3 ML after annealing at 800 °C whereas a (1×3) phase grows on top of this with θ≥1.0 ML coverage in agreement with LEED data. It was also observed that the (2×3) phase formation is critical to the Sr coverage and to the annealing temperature as well. The relationship between the (2×3) and (1×3) ordered structures has been investigated as a function of Sr coverage and annealing temperature.

Growth and interfacial properties of epitaxial oxides on semiconductors: ab initio insights

“…For deposition at room temperature and for low Sr coverages up to 0.5 ML, electron diffraction indicates that the underlying Si surface retains the same 2 9 1 symmetry of the bare dimerized Si (001) surface [15]. In addition, STM images are consistent with Sr adatoms being adsorbed on top of the dimerized Si surface [24]. The Sr adatoms tend to form diagonal chains on the surface but with no long range order.…”

“…STM images of this 1/6 ML reconstruction show an ordered 2 9 3 pattern with strong bias dependence (see Fig. 5) [24][25][26]. Results at even higher temperatures (800°C) show that this 2 9 3 reconstruction can be reversibly melted and reformed, and its temperature versus coverage phase boundary has been measured [29].…”

“…The resulting low energy configurations of the surface Sr consist of diagonal chain-like structures for coverages ranging from 1/6 to 1/4 ML (See Fig. 3) [16,24]. There is a very small energy difference between straight chains and zig-zag chains (compare Fig.…”

“…A variety of experimental techniques have been used to characterize the submonolayer Sr-on-Si surface, including reflection high energy electron diffraction (RHEED) [5,14,15], low energy electron diffraction (LEED) [18], scanning tunneling microscopy (STM) [24][25][26], photo-emission spectroscopy (PES) [27], and synchrotron X-ray diffraction (XRD) [28]. For deposition at room temperature and for low Sr coverages up to 0.5 ML, electron diffraction indicates that the underlying Si surface retains the same 2 9 1 symmetry of the bare dimerized Si (001) surface [15].…”

STM and DFT study on formation and characterization of Ba-incorporated phases on a Ge(001) surface

“…At coverages below 0.5 monolayer (ML) these elements were shown to form two adsorption structures on Si(001) and Ge(001)-namely the on-top and incorporated phases [15,19]. The on-top phase on Si(001) was observed for the room temperature (RT) adsorption of Ba, Li, or Sr atoms in the form of randomly distributed chains of the adatoms that run across the Si dimer rows [19][20][21][22][23]. The analogous phase formed by the Ba adatoms on Ge(100) was demonstrated to consist of the Ba ad-dimers [24].…”