Portland State University. Department of Physics
Date of Award
Master of Science (M.S.) in Physics
1 online resource (vi, 65 pages)
Microscopes -- Design and construction, Microscopy -- Research, Photomicrography, Scattering (Physics) -- Research
This work presents a new form of microscopy, the instrument constructed to demonstrate it, the images produced and the image contrast mechanisms seen for the first time. Some of its future scientific potential is described and finally, recent work towards advancing the method is discussed.
Many forms of microscopy exist, each with unique advantages. Of several broad categories that they could be grouped into, those that use particle beams have proven very generally useful for micro and nano-scale imaging, including Scanning Electron, Transmission Electron, and Ion Beam microscopes. These have the disadvantage, however, of implanting electric charges into the sample, and usually at very high energy relative to the binding energy of molecules. For most materials this modifies the sample at a small scale and as we work increasingly towards the nano-scale, this is a serious problem.
The Neutral Atom Microscope (NAM) uses a beam of thermal energy (under 70 meV) non-charged atoms or molecules to probe an atomic surface. For several decades scientists have been interested in this possibility, using a focused beam. Scattering of neutral atoms provides a uniquely low-energy, surface-sensitive probe, as is known from molecular beam experiments.
We have developed a new approach, operating with the sample at a close working distance from an aperture, the need for optics to focus the beam is obviated. The demonstrated, practical performance of this "Pinhole" NAM exceeds all other attempts by great lengths by many measures. The unique images resulting and contrast mechanism discoveries are described. The future potential for nano-scale resolution is shown.
Witham, Philip James, "Pinhole Neutral Atom Microscopy" (2013). Dissertations and Theses. Paper 1407.