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oai:drum.lib.umd.edu:1903/24692016-03-29T06:49:22Zcom_1903_2269com_1903_12com_1903_2col_1903_2800col_1903_3

Anlage, Steven M Imtiaz, Atif Digital Repository at the University of Maryland University of Maryland (College Park, Md.) Physics 2005-08-03T14:19:51Z 2005-08-03T14:19:51Z 2005-04-21 http://hdl.handle.net/1903/2469 A novel Near-Field Scanning Microwave Microscope (NSMM) has been developed where a Scanning Tunneling Microscope (STM) is used for tip-to-sample distance control. The technique is non-contact and non-destructive. The same tip is used for both STM and NSMM, and STM helps maintain the tip-to-sample distance at a nominal height of 1 nm. Due to this very small tip-to-sample separation, the contribution to the microwave signals due to evanescent (non-propagating) waves cannot be ignored. I describe different evanescent wave models developed so far to understand the complex tip-to-sample interaction at microwave frequencies. Propagating wave models are also discussed, since they are still required to understand some aspects of the tip-to-sample interaction. Numerical modeling is also discussed for these problems. I demonstrate the sensitivity of this novel microscope to materials property contrast. The materials contrast is shown in spatial variations on the surface of metal thin films, Boron-doped Semiconductor and Colossal Magneto-Resistive (CMR) thin films. The height dependence of the contrast shows sensitivity to nano-meter sized features when the tip-to-sample separation is below 100 nm. By adding a cone of height 4 nm to the tip, I am able to explain a 300 kHz deviation observed in the frequency shift signal, when tip-to-sample separation is less than 10 nm. In the absence of the cone, the frequency shift signal should continue to show the logarithmic behavior as a function of height. I demonstrate sub-micron spatial resolution with this novel microscope, both in tip-to-sample capacitance Cx and materials contrast in sheet resistance Rx. The spatial resolution in Cx is demonstrated to be at-least 2.5 nm on CMR thin films. The spatial resolution in Rx is shown to be sub-micron by measuring a variably Boron-doped Silicon sample which was prepared using the Focus Ion Beam (FIB) technique. 52771539 bytes application/pdf en_US Quantitative Materials Contrast at High Spatial Resolution With a Novel Near-Field Scanning Microwave Microscope Dissertation Physics, Optics Physics, Condensed Matter Physics, Electricity and Magnetism Near-Field Microscopy Microwaves STM Evanescent Semiconductors CMR open.access