Rotational Transition of Incommensurate Kr Monolayers on Graphite

Synchrotron x-ray diffraction studies of the orientational epitaxy of krypton on single-crystal graphite are reported. The system displays a continuous transition from an aligned to a rotated orientation with increasing mean misfit in a manner predicted by a hexagonal-domain-wall model of the weakly incommensurate phase. A hysteresis at the critical misfit is observed. The results are discussed in light of current views of the structure of the incommensurate phase.