These pictures show 5 um x 5 um topographic maps obtained with an Atomic Force Microscope (AFM) of thin films of the semiconductor CuCl grown on insulating CaF2(111) single crystal substrates. The z-scale is magnified 3 times to increase the vertical contrast in the images. Samples with prefaces A and B were grown at substrate temperatures of 110deg. C and 80deg.C, respectively, which represent the upper and lower limits at which it is possible to deposit crystalline CuCl and have it stick to the substrate. Samples with suffices 1, 2, and 3 received total molecular fluences equivalent to the deposition of 6nm, 12nm, and 40nm of uniform CuCl films and represent the island nucleation, growth, and coalescence regimes of heteroepitaxial growth, respectively. X-ray diffraction analysis of the films indicates that the CuCl is single crystal and present in only one orientation on the substrate. Although the crystal structures of the two materials are different (CuCl is zinc blende whereas CaF2 is the fluorite structure), both have cubic unit cells with almost identical lattice constants (~5.45Å). These AFM topographs were collected as part of a study to understand the basic kinetic mechanisms of growth that determine the morphology of the surface of a film for heteroepitaxial deposition (i.e. a crystalline film of one material grown on top of a single crystal substrate of a different material). For this purpose, very rough surfaces that are nearly fractal in nature contain a great deal of valuable information about growth that can be extracted by quantitative analysis of the numerical values of the topographs. For further information, please see the following references or contract Prof. Williams at the UCLA Department of Chemistry and Biochemistry:
R. S. Williams, David K. Shuh, and Y. Segawa, J. Vac. Sci. Technol. A, 6, 1950 (1988).
E. A. Eklund, R. Bruinsma, J. Rudnick and R. S. Williams, Phys. Rev. Lett., 67,1759 (1991).
W. M. Tong, E. J. Snyder, R. S. Williams, A. Yanase, Y. Segawa, and M. S.Anderson, Surf. Sci. Lett., 227, L63 (1992).
W. M. Tong, R. S. Williams, A. Yanase, Y. Segawa, and M. S.Anderson, Phys. Rev. Lett., (1994 - in press).
W.M. Tong and R. S. Williams, Ann. Rev. Phys. Chem., (1994 - in press).