Terrace Width Distribution Research Articles

High resolution measurement of the step distribution at the Si/SiO2 interface

With a recently developed high resolution LEED instrument spot profiles of the 00–beam of Si/SiO2 interfaces have been taken after the removal of the oxide. It is demonstrated, that beyond the half-width the full profile down to a hundredth of peak intensity gives valuable information. The distribution of terraces up to more than 50 nm contribute essentially to a sharp central spike, which is only visible with a high resolution system. Whereas with usual LEED optics only terraces up to about 20 nm are evaluated from spot profile, the present data for the first time allow an evaluation in an extended range of terrace widths besides step atom density. Model calculations show the influence of instrument response and of details of the terrace width distribution on the spot profile.

Landau-Lifshitz analysis for stepped surfaces

We consider phase transitions on stepped surfaces. The Landau-Lifshitz rules are used as criteria for determining those (commensurate) superlattice structures that are “allowed”, i.e., may be reached by continuous phase transitions. The problem is reduced to an essentially two-dimensional case which allows one to make use of the results of Rottman. Tables of all possible allowed (commensurate) structures (with scalar order parameters) are given, along with a step-by-step procedure for determining whether a given superlattice structure on a given stepped surface is allowed. Some examples are treated in detail. It is also determined that all allowed transitions are in either the Ising or Xminus; Y with cubic anisotropy universality classes. The effects of random fields generated by non-uniform terrace width distributions are also mentioned.

Atomic correlations of stepped surfaces and interfaces

We have developed a scheme to evaluate the atomic pair correlation function exactly for stepped surfaces and interfaces. This pair correlation function is particularly useful in calculating the diffracted beam width and shape from an arbitrary distribution of steps using low-energy electron diffraction, reflection high-energy electron diffraction, and grazing x-ray diffraction. We have made model calculations for several realistic terrace width distributions. By comparing the calculated and measured diffracted beam widths and shapes, one can extract valuable, quantitative structural information on surfaces, interfaces, and epitaxially grown films.

Quantitative evaluation of random distributed steps at interfaces and surfaces

LEED spot profiles are evaluated to determine random distributed steps at interfaces and surfaces. It is shown that strictly kinematical evaluations are sufficient to provide data on step atom density and terrace width distribution. Experimental results for samples prepared in different ways show the wide range of applications.