Coherent soft x-ray scattering from InP islands on a semiconductor substrate

Coherent soft x-ray scattering experiments from a semiconductor sample cons isting of InP islands on a smooth semiconductor substrate are described. Th e soft x-ray scattering was performed with 266 eV photons produced by an un dulator source. Using a position sensitive detector, we are able to detect diffusely scattered x rays in the vicinity of the specular reflection, with an in-plane momentum transfer of up to 6 mu m(-1). Using Huygens-Fresnel t heory and atomic force microscope images of the surface structure, we simul ated the scattering assuming a finite lateral coherence length for the inci dent radiation. The lateral coherence length of the incident beam was found to be 20 mu m from a fit to the observed diffraction pattern from a pinhol e. The effect of changes in the surface morphology on the speckle pattern w as simulated to explore the potential of coherent soft x-ray scattering for the study of surface structure dynamics. (C) 1999 American Vacuum Society. [S0734-211X(99)03704-X].