Intra- and interlayer atom-atom correlations in molecular beam epitaxially grown dilute InGaAs alloys were studied using cross-sectional scanning tunneling microscopy. By imaging individual chemical constituents we construct a large ensemble of “atom maps” from which two-dimensional In-In pair correlation functions were deduced. We found a total absence of interlayer pair correlation along $\left[001\right]$ and a strong negative correlation for the nearest neighbor (nn) pair along $\left[110\right]$, corresponding to a repulsive interaction energy of 0.1 eV for the nn In pairs along $\left[110\right]$. In addition, a weak long-range oscillation in the correlation function along $\left[110\right]$ is observed.

• Received 11 July 1997

DOI:https://doi.org/10.1103/PhysRevLett.79.4822