IMR: Development of an Imaging Transport Instrument for Materials Research and Education

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An Integrated Transport System will be developed in a scanning electron microscope (SEM) to perform optical imaging of transport phenomena. The system will provide direct imaging of carrier diffusion and drift, charge injection and transport in low dimensional structures via the spatial imaging of luminescence associated with free charge recombination. Transport imaging within the SEM can be applied to any material with a luminescent signature and will achieve spatial resolution and control that is difficult to obtain with optical systems. The system will have variable temperature (300 to 5 K) capability and combined options for SEM and cathodoluminescence imaging. An internal near-field optical system will extend the resolution limit to ~ 50 nm. Research is proposed, using this new capability, in the areas of transport in quantum wires, contact-free measurements of transport parameters, near-contact behavior and transport studies in wide bandgap materials. The instrument will contribute to the integration of research and education by bringing together undergraduate and graduate students, faculty and industrial scientists. The grant will support existing outreach efforts to underrepresented groups at UC Berkeley and provide unique opportunities for interaction with diverse students at the Naval Postgraduate School (NPS) representing all branches of the US military and a broad international community. An Integrated Transport System will be developed to allow for direct imaging of the motion of free charge (e.g. electrons) within materials designed for optoelectronic applications. The system will combine two microscopes (a scanning electron microscope (SEM) and an optical microscope) to enable the direct imaging of electron motion due to diffusion and to movement in an electric field. These phenomena are at the heart of the operation of all photon sources and detectors. The technique works by imaging the light emitted when free charges recombine and can be applied to any material that emits light under electron beam excitation. One primary goal of the project is to extend the existing capability of transport imaging to the high resolutions (~ 50 nm) needed for characterization of nanotechnology structures. This will be done by introducing near-field optics, which allow for resolution beyond the normal limits imposed by diffraction. Research using the new equipment will be performed on quantum wires, solar cell materials, and newer semiconductor materials for application to biochemical sensing. The instrument will contribute to the integration of research and education by bringing together undergraduate and graduate students, faculty and industrial scientists in collaborative projects. The grant will support existing outreach efforts to underrepresented groups at UC Berkeley and provide unique opportunities for interaction with diverse students at the Naval Postgraduate School representing all branches of the US military and a broad international community.