doi:10.1016/S0039-6028(98)00658-X 
Copyright © 1998 Elsevier Science B.V. All rights reserved
Evolution of surface morphology of vicinal Si(111) surfaces after aluminum deposition
C. Schwennicke, X. -S. Wang1, T. L. Einstein and E. D. Williams*
Department of Physics, University of Maryland, College Park, MD 20742-4111, USA
Received 9 March 1998;
accepted 13 August 1998.
Available online 8 October 1999.
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Abstract
We have studied changes in surface morphology of vicinal Si(111) surfaces with a miscut of 1.3° in the 
direction after Al deposition at elevated temperatures. The clean surface phase separates into a (111)-oriented phase and a stepped phase. Submonolayer Al deposition at 650°C, the normal preparation temperature of the Al/Si(111)-
R30° structure, only induces minor changes in the surface morphology. However, after Al deposition at temperatures above the order–disorder phase transition temperature, the step bunches break apart into a uniform array of single height steps with an average step–step separation determined by the macroscopic miscut. From a quantitative analysis of the amount of meandering of steps and the terrace width distribution, we determined the diffusivity of steps and the strength of the repulsive step–step interaction. The repulsive interaction between steps is enhanced by the Al adsorption compared to both the high-temperature (1×1) and (7×7) phases of the clean surface.
Author Keywords: Aluminum; Epitaxy; LEED; Scanning Tunneling Microscopy; Silicon; Stepped single crystal surfaces; Surface morphology; Surface thermodynamics; Vicinal single crystal surfaces
Fig. 1. 4000×4000 Å2 STM image of a clean Si(111) surface with a miscut of 1.3° towards the direction. Terraces with an average width of about 900 Å are separated by step bunches containing six to 10 single-layer-height steps. Occasionally, crossing steps with a single-layer height are observed, as can be seen on one of the terraces. The direction is orthogonal to the average step edges and in the downhill direction.
Fig. 2. 2800×2800 Å2 STM image of a Si(111) surface with a miscut of 1.3° towards the direction after deposition of a third of a monolayer of aluminum at a temperature of 770°C. After deposition, the sample was quenched to room temperature. The image was taken at room temperature. The surface now consists of an array of single-layer-height steps. The initial positions of the step bunches are no longer visible. The direction is orthogonal to the average step edge direction and in the downhill direction.
Fig. 3. Empty-state STM image of the same sample as in Fig. 2. The scan size is 135×135 Å2, the tip bias is −2 V, and the tunneling current is 1 nA. The direction is oriented from left to right in this image.
Fig. 4. Step correlation function F(y)=
[x(y)−x(0)]2
averaged over 30 steps and a total step length of about 3 μm. The straight line is a fit to the data for small values of y.
Fig. 5. Distribution of the terrace widths after deposition of a third of a monolayer of aluminum at 770°C and subsequent quenching to room temperature. Data are averaged over three images containing a total number of 60 steps. Error bars are calculated assuming the relative error to be where N is the number of observations for a given terrace width. The solid line is a fit to a Gaussian distribution. Fit parameters are the width w=32.3±1.2 Å and the average interstep distance =136±2 Å.
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and the rescaled (dimensionless) Gaussian width of the terrace width distribution (TWD) w/
