Fluctuation Electron Microscopy Investigations of Medium Range Order in a-Silicon and a-Silicon:hydrogen Thin Films

83 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006.The first practical version of variable resolution fluctuation electron microscopy has been developed on the JEOL 2010F transmission electron microscope in the Center for Microanalysis of Materials, UIUC. This technique provides information on the spatial extent of the medium range order. Nanodiffraction patterns are obtained using electron probes with a full width at half maximum between 1--4 nm. A convenient method of forming coherent nanoprobes has been developed where the probes are obtained by varying the condenser minilens excitations and the condenser aperture size. The patterns are quantitatively analyzed to get medium range order statistics. Data from amorphous silicon samples grown by different techniques show varying sensitivities to the medium range order depending on the probe size. The application of the pair persistence formulation on the data shows a difference in the characteristic length scales of the ordered regions between the two samples.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD