X-ray Speckles Show Steps and Deformations Moving in Concert

Surface x-ray diffraction speckles allow us to observe the motion of nanoscale boundaries such as steps as they pass through an illumination window. Each step passing through the window causes an oscillation of x-ray intensity. In addition, surface x-ray speckles, due to the atomic-level sensitivity of x-rays, can detect subtle but important details of the moving steps. By analyzing the surface x-ray speckles, researchers at Argonne National Laboratory find that a platinum layer reconstructs as it emerges to become the top surface and severely deforms at the edge of the upper layer to accommodate the reconstruction and associated expansion. Furthermore, these deformations travel in concert with the step edges as they retract due to sublimation at high temperatures. These reconstructions and deformations are critical factors affecting transition metals’ catalytic and energy-conversion activities.



  • Reference:
  • Pierce, M., Hennessy, D., Chang, K.-C., Komanicky, V., Strzalka, J., Sandy, A., Barbour A., You, H., “Persistent Oscillations of X-ray Speckles: Pt (001) Step Flow,” Appl. Phys. Lett., in press (September, 2011).