W. C. Fan

Identification of ordered atomic structures of Ba on the Si(100) surface

Abstract Three long-range ordered atomic structures of (2 × 3), (1 × 2) and (2 × 4) phases have been observed by low-energy electron-diffraction (LEED) in the Ba/Si(100) surface at submonolayer Ba coverages (θ 2 ML), which might result from Ba diffusion and possible formation of a barium suicide.

Reconstruction of the Si(111) surface induced by alkali metals

Abstract Both (1 × 3) and (√3 × √3)R30° reconstructions of the Si(111) surface induced by Li, K and Cs depositions have been studied by low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). It has been found that measured LEED I-V curves for (1 × 3) reconstruction induced by different alkali metals are virtually identical to each other, which suggests that the (1 × 3) structures of the Si(111) reconstruction induced by different alkali metals are nearly identical. Work-function measurements indicating alkali-metal coverages of near 0.1 ML for the (1 × 3) structures, excluded the possibility of long-range ordered structures of Li in the (1 × 3) reconstruction. The measured I-V curves of the Li-induced (√3 × √3 )R30° reconstruction are similar to those of Ag-induced (√3 × √3)R30° structures, indicating similarity between the (√3 × √3) structures.

Oxidation of the Si(100) surface promoted by Sr overlayer : an x-ray photoemission study

The interaction of strontium overlayers with atomically clean Si(100) surface has been studied by x‐ray photoelectron spectroscopy. Also studied were the effects of Sr overlayers on the oxidation of silicon at different Sr coverage (0≤θ≤1.85) and different oxygen exposure. It is found that at low coverage, θ≤1 monolayer (ML), Sr interacts with the Si(100) surface to form a strong ionic bond. Also, Sr is found to significantly increase the oxidation of the Si(100) surface. Silicon oxidation increased with increasing Sr coverage to a maximum at θ≊1 ML. Above 1‐ML Sr coverage, the rate of Si oxidation decreased with increasing coverage.

Growth of bismuth on the Si(100) surface: AES and LEED study

Abstract The growth of Bi on the Si(100)-(1 .> 2) surface has been investigated with low energy electron diffraction (LEED) and Auger electron spectroscopy (AES) at temperatures between 80 and 1200 K. The deposition of Bi atoms onto the substrate at temperatures above 280 K first resulted in a (1 × 1) substrate reconstruction at about 1 ML Bi exposure, followed upon further exposure by Bi island formation of the Stranski-Krastanov (SK) type. Bi overlayers deposited on the Si(100) substrate at temperatures below 280 K were found to be disordered and uniform. Dramatic aggregation of Bi atoms in the disordered overlayers ( > 1 ML) was observed by both LEED and AES at a temperature of about 300 K. Scanning electron microscope (SEM) images further confirmed Bi island growth.

Epitaxial and interface properties of InAs/InGaSb multilayered structures

We have used the technique of molecular beam epitaxy to grow InAs on GaSb, GaSb on InAs, and InAs/InxGa1−xSb (0≤x≤0.4) multilayered structures and have performed a detailed investigation of the layers and resultant interfaces. The structures were grown on (100) oriented GaSb or GaAs substrates. Combined reflection high energy electron diffraction, x‐ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES) studies indicate that Sb is persistently present on the InAs growth surface. XPS and AES analysis of InAs/GaSb heterojunctions indicates no compound formation at either the InAs/GaSb or GaSb/InAs interface. Secondary ion mass spectroscopy (SIMS) and XPS extinction profiles reveal the presence of approximately 5–10% As in the nominally pure GaSb layers. Analysis of InAs/GaSb/GaSb (100) structures by SIMS indicates that the As is incorporated during growth. The multilayer structures have been characterized by double crystal x‐ray diffraction and the data has been modeled using kinematic ...

Island formation of aluminum on the graphite (0001) surface: Leed and AES study

Abstract The analysis of island formation of aluminum on graphite (0001) has been carried out with LEED and AES. At submonolayer coverages and monolayer coverage, there were no superstructures observed and LEED dynamical calculation results for several structural models further confirmed no p(1 × 1) structures. Both LEED and AES intensity analysis as a function of Al exposure support the model that Al atoms aggregate to form Volmer-Weber type islands on the graphite surface.

Ordered phases and phase transitions of cesium on the Cu(111) surface

Low‐energy electron diffraction (LEED) experiments have been carried out to study the ordered phases and phase transitions of cesium on the Cu(111) surface in the temperature region between 80 and 450 K. The cesium on the 80‐K surface forms an orientationally ordered incommensurate structure (IS) at coverage θ>0.12. The overlayer lattice parameter of the IS phase decreases continuously with coverage until a Cs–Cs spacing 7% smaller than in bulk cesium is reached. By increasing the temperature, the IS phase undergoes several transitions as a function of coverage: (i) a better ordered phase at 135 K, (ii) a disordered phase through an intermediate phase (‘‘hexatic’’ phase) at θ 0.21, and (iii) a (2×2) phase at θ>0.25 and T≊260 K and a (6×6) phase at T≊355 K. The cesium on the surface also forms an antisymmetrical metallic domain phase and a coexisting phase of ( (4)/(3) (3)1/2× (4)/(3) (3)1/2)‐R30° and (2×2).

The effect of Sr and Bi on the Si(100) surface oxidation: Auger electron spectroscopy, low energy electron diffraction, and x‐ray photoelectron spectroscopy study

The effect of Sr and Bi on the oxidation of the Si (100) surface has been studied by Auger electron spectroscopy, low electron diffraction, and x‐ray photoelectron spectroscopy. A dramatic enhancement, by a factor of 10, of the Si oxidation has been observed for Si(100) with a Sr overlayer. The SR‐enhanced Si oxidation has been studied as a function of O2 exposure and Sr coverage. In contrast to the oxidation promotion of Sr on Si, it has been also observed that a Bi overlayer on Si(100) reduced Si oxidation significantly. Sr adsorption on the Si(100) with a Bi overlayer enhances Si oxidation only at Sr coverage θSr >0.3 ML.

Reflection high‐energy electron diffraction study of growth and interface formation of the Ga1−xInxSb/InAs strained‐layer superlattices

Growth and interface formation of the Ga1−xInxSb/InAs (x≤0.4) strained‐layer superlattices (SLSs) on GaSb(100) substrates have been studied by the reflection high‐energy electron diffraction (RHEED) during molecular beam epitaxy. A number of surface atomic structures were observed in the growth of the SLS: a (1×3) phases from the InAs epilayer surface; a (2×3) phase, a (2×4) phase and diffuse (1×1)‐like phases from the InAs epilayer surface. The RHEED intensity variations in the formation of the interfaces have been discussed in terms of interface chemical reactions.

Adsorption of Ba on the GaAs(110) surface and its effect on surface oxidation

Adsorption of Ba and its effect on the GaAs(110) surface oxidation has been studied by low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). The Ba adsorption onto the surface results in a disordered interface of Ba and the GaAs surface at temperatures <500 °C. However, the reactivity of the GaAs surface to oxygen is dramatically enhanced by the adsorbed Ba atoms. This enhancement of the surface oxidation is proportional to the Ba exposure. Study of LEED and AES intensities has also revealed evidence of Ba‐induced surface disorder on the GaAs.