Distinguishing step relaxation mechanisms via pair correlation functions

TL;DR

This study uses STM measurements to analyze step fluctuations on Si(111)-Al surfaces at high temperature, testing theoretical models of coupled step motion and relaxation mechanisms.

Contribution

It provides experimental evidence that near-neighbor step fluctuations are uncorrelated and challenges the predicted t^1/2 growth of pair correlations from atomic diffusion models.

Findings

Pair-correlation functions are within one standard deviation of zero.

No significant t^1/2 growth observed in pair correlations.

Uncorrelated step fluctuations occur via random attachment/detachment events.

Abstract

Theoretical predictions of coupled step motion are tested by direct STM measurement of the fluctuations of near-neighbor pairs of steps on Si(111)-root3 x root3 R30 - Al at 970K. The average magnitude of the pair-correlation function is within one standard deviation of zero, consistent with uncorrelated near-neighbor step fluctuations. The time dependence of the pair-correlation function shows no statistically significant agreement with the predicted t^1/2 growth of pair correlations via rate-limiting atomic diffusion between adjacent steps. The physical considerations governing uncorrelated step fluctuations occurring via random attachment/detachment events at the step edge are discussed.