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3D Tomographic Scanning Microwave Microscopy with Nanometer Resolution



OBJECTIVE: Develop near-field scanning microwave microscopy hardware and software to enable 3D tomographic imaging of the structural and electromagnetic properties of electronic and biological materials with nanometer spatial resolution. 

DESCRIPTION: Near-field scanning microwave microscopy (SMM) is a new atomic-scale scanning probe capable of penetrating below the sample surface up to one micrometer in depth. Compared to optical, x-ray or electron microscopy, SMM is highly non-invasive because the energy of microwave photons is only on the order of 10 µeV. Therefore, the technique can potentially be very useful in imaging the structural and electromagnetic properties for a wide range of electronic and biological materials with high electrical and spatial resolution, and provide unique insights into their fundamental characteristics. To date, sophisticated probes and complete systems have been offered, and different probe calibration and data analysis approaches have been proposed, and promising results have been demonstrated. For example, SMM has been used to image the quantum Hall edge states in graphene and topological insulators, and for biological applications, to investigate the effect of fullerene nanoparticles on breast cancer cells. The high sensitivity of SMMs can also potentially enable direct imaging of ion channel and nanoporation in a cell membrane. Furthermore, recent demonstration of SMM operating in liquid environment will open up even more opportunities in biology and medical science. In addition to the aforementioned advances, SMM offers the unique capability of penetrating into the sample-under-test in a non-invasive and non-contacting manner. This feature allows imaging of sub-surface structures, and open the possibility for 3D tomography with nanometer resolution. The tomographic potential of SMM has been demonstrated in proof-of-principle experiments. In these experiments, broadband or multi-frequency microwave radiation was used to probe different sample depths. Despite these promising results, 3D tomographic SMM systems for consistent and reproducible characterization are still not available. The goal of this project is to develop reliable and user-friendly SMM systems with 3D tomography capability. This will still require major improvements in both hardware and software. 

PHASE I: Define system architecture both in hardware and software which shows feasibility of obtaining 10 nm resolution in all three spatial dimensions. Include determination of optimum system frequency, bandwidth, and data analysis in frequency domain vs. time domain. Determine advantages of operating at higher frequencies such as millimeter-wave and terahertz frequencies for improving system performance. Perform 3D electromagnetic designs of the probe structures to be integrated with system. At least one of the probe designs should be compatible with liquid environment. Investigate innovative micro-machining techniques for realizing the probe designs. Explore new software algorithms for 3D image reconstruction. 

PHASE II: Implement designs including both hardware and software from Phase I to construct an SMM with 3D tomography capability. Demonstrate reproducible characterization of biological or electronic samples with 3D resolution 10 nm or less. Collaborate with biomedical or electronic researchers to demonstrate the 3D advantage of the technique. Modify the hardware and software as needed and document the modifications. 

PHASE III: High-resolution and non-invasive 3D microscopic tools for biomedical and electronic scientific research, industry applications and defense systems. Applications include characterization of semiconductor, metal, organic films, etc., and detection of counterfeit integrated circuits. Beyond material characterization, it also provides unique capability for identification of chemical/bio agents and biomolecules. 


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KEYWORDS: Sensors, Electronics; Battle Space Environment 

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