# In Situ Microbeam Surface X-ray Scattering Reveals Alternating Step Kinetics During Crystal Growth Source: [In Situ Microbeam Surface X-ray Scattering Reveals Alternating Step Kinetics During Crystal Growth]() Collection index: [llms.txt]() Data updated: 2025-10-28T13:54:23.711Z Authors: Guangxu Ju, Dongwei Xu, Carol Thompson, Matthew J. Highland, Jeffrey A. Eastman, Weronika Walkosz, Peter Zapol, G. Brian Stephenson Published: 2020-07-09T22:02:40.000Z ## Abstract The stacking sequence of hexagonal close-packed and related crystals typically results in steps on vicinal {0001} surfaces that have alternating A and B structures with different growth kinetics. However, because it is difficult to experimentally identify which step has the A or B structure, it has not been possible to determine which has faster adatom attachment kinetics. Here we show that in situ microbeam surface X-ray scattering can determine whether A or B steps have faster kinetics under specific growth conditions. We demonstrate this for organo-metallic vapor phase epitaxy of (0001) GaN. X-ray measurements performed during growth find that the average width of terraces above A steps increases with growth rate, indicating that attachment rate constants are higher for A steps, in contrast to most predictions. Our results have direct implications for understanding the atomic-scale mechanisms of GaN growth and can be applied to a wide variety of related crystals. ## Recorded benchmark results A research result applies to its stated dataset, split, metric and evaluation configuration. Compare like-for-like settings, preserve the metric's unit and direction, and distinguish paper-reported results from independent reproduction. The best result recorded here is not a claim of exhaustive, current global coverage. ## Original sources and implementation [Original paper]() [PDF]()