9526100 Spence This project addressees research into fundamental atomic processes responsible for dislocation motion in semiconductors, and into the mechanism of surfactant action in controlling layer-by-layer epitaxial crystal growth. Two research aspects being emphasized are: (1)direct observation of kinks in motion on dislocations by atomic resolution electron microscopy using "forbidden" reflection TEM lattice imaging in silicon at 600C; pinning mechanisms of kinks and the correlations of kinks on different partial dislocation, and factors which ultimately control the ductility of crystals at the atomic level are of basic interest. (2) a recently developed Scanning Atom Probe (SAP) which allows groups of atoms from identified sites in an STM image to be ejected into a time-of-flight mass analyzer for chemical identification, will be used to study surfactant action during the growth of Ge on Si, and to test theories of surfactant action in the early stages of low-temperature epitaxial growth. Theoretical analyses, e.g., ab-initio computations of kink mobility, are an integral part of the project. %%% A Scanning Atom Probe (SAP) has recently been developed and will be used for basic research studies of surfactant mediation during epitaxial crystal growth of electronic and photonic materials. Both SAP and high resolution electron microscopy will be used to study the motion of atomic defects, and additional atomic level phenomena that ultimately control macroscopic material properties. An important feature of the program is the training of graduate and undergraduate students in a fundamentally and technologically significant area. *** .
