Patterns in the atomic dance: coherent x-rays reveal interlayer correlations in islands during crystal growth

February 11, 2019

In a study published in Nature Physics, researchers pioneered, with the worldwide advent of new coherent X-ray sources, the experimental and analysis methods will enable broad application of XPCS to observe atomic-scale processes on surfaces.

a,b, Two-time correlations C(t1,t2) in the measured speckle from 2D islands before, during, and after growth at 796 K (a) and 867 K (b). The time axes have been converted to growth amount using the observed growth rate (Supplementary Table 2). White lines indicate the start and end of growth. The ‘checkerboard’ pattern indicates that the arrangement of islands formed in successive layers is correlated with that in previous layers.

Scientific Achievement

Using X-ray Photon Correlation Spectroscopy (XPCS), we observe correlations between arrangements of monolayer-height islands on succeeding layers during vapor phase epitaxy of GaN.

Significance and Impact

These first XPCS measurements of 2D island dynamics during layer-by-layer growth demonstrate the ability to observe fluctuation dynamics of weakly scattering surface features in operating and synthesis environments.

Research Details

High-energy XPCS using high-intensity “pink beam” was developed to enable in situ observation of atomic-scale surface dynamics.
Two-time correlations revealed persistence in arrangement of islands formed on each monolayer during crystal growth.
Kinetic Monte-Carlo modeling predicted conditions for persistence and identified atomic-scale mechanisms responsible.

DOI: 10.1038/s41567-019-0448-1

Download this highlight

Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science.

The U.S. Department of Energy’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit https://energy.gov/science.