Aberration-Corrected Photoelectron Microscope: Opening the Nanometer Scale for Organic Matter Microscopy

Portland State University, Portland OR

Investigators

Abstract

This award supports the development of a stand-alone aberration-corrected photoelectron microscope (PEM), capable of 2 nm spatial resolution. Photoelectron microscopes combine the advantages of sample exposure by light and the high-resolution capabilities of imaging with electrons. These unique features are of particular interest in biology since they allow the damage-free study of soft organic matter at very high resolution. The resolution of the proposed microscope will be comparable to the best attainable with scanning electron microscopes. Yet the ultraviolet (uv)-excitation of photoelectron microscopes is considerably less damaging than the electron exposure in scanning electron microscopes, particularly when a narrow electron beam is used as in high-resolution work. Photoelectron microscopy also allows a number of imaging modes, which are not accessible with scanning electron microscopes. These imaging modes include specific chemical, physical, and topographical contrast modes as well as advanced operation with incorporated markers. These features can be used to obtain strong functional contrast in tissues of similar atomic composition. At present no other light-optical excitation technique is capable of better resolution. The physical design of the instrument will incorporate a hyperbolic electrostatic mirror to correct the spherical and chromatic aberrations of an electrostatic lens system. A Y-shaped beam line with symmetric small-angle deflections will allow a compact design, compatible with typical laboratory dimensions. This work will bring together an interdisciplinary team of engineers, technicians, and scientists from within the university and from industry. Students at all levels (high-school, undergraduate, graduate, postgraduate) will be involved in and/or exposed to the technology development effort.