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Quantitative Materials Contrast at High Spatial Resolution With a Novel Near-Field Scanning Microwave Microscope

dc.contributor.advisorAnlage, Steven Men_US
dc.contributor.authorImtiaz, Atifen_US
dc.description.abstractA 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.en_US
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dc.titleQuantitative Materials Contrast at High Spatial Resolution With a Novel Near-Field Scanning Microwave Microscopeen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.subject.pqcontrolledPhysics, Opticsen_US
dc.subject.pqcontrolledPhysics, Condensed Matteren_US
dc.subject.pqcontrolledPhysics, Electricity and Magnetismen_US
dc.subject.pquncontrolledNear-Field Microscopyen_US

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