Development of a Near-Field Scanning Photoemission Microscope for Materials Identification and Dopant Imaging and Student Training

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This grant will provide partial support for the development of a near-ultraviolet, near-field-scanning-optical-microscope system using the probe as a collector of photoelectrons with ~10-50 nm resolution in three dimensions will be developed. Voltage biasing of the probe will be used for voltage-assisted photoemission and, through the unique geometry provided the metal probe aperture in close proximity to the surface, the voltage bias can drive a field internal to a semiconductor. The latter capability permits measurement of the local dopant density. Materials systems impacted by this instrument include:1) Materials identification in sample volumes approaching 102 nm3. This addresses a long-standing weakness of the scanning probe microscopes - that material identification of unknown samples is difficult and/or slow. The instrument will enhance ongoing studies of particulate matter from the air.2) Single dopant imaging in semiconductors under ambient conditions. Counting dopant atoms is perhaps the ultimate way to study dopant distributions near surfaces. This instrument will permit such studies in air, on industrially relevant samples.3) High-resolution dopant profiles in two dimensions. The next few generations of devices require imaging metrology of dopant profiles on the 10-50 nm resolution level. There are not many techniques that can hope to successfully perform such mapping. This instrument opens a unique venue to such measurements, and will impact device research on silicon and gallium nitride.4) Passivation of semiconductor surfaces is very important in optoelectronic devices. This instrument will pinpoint defects in the passivation at high resolution so that their nature can be identified and actions taken to correct the process. Currently, efforts in wide bandgap systems are in need of such instrumentation.5) Educational opportunities arise from the training of the students involved and from use of the instrument in an advanced teaching laboratory environment. The latter will elucidate the materials effects in the behavior of metal-insulator-semiconductor devices through its unique variable geometry that allows changes in the ratio of voltage dropped in air to that dropped in the semiconductor. It will also be used in the course to investigate voltage-assisted photoemission.%%%The development of this system will significantly enhance research capabilities and educational opportunities for students.