Low energy electron point source (LEEPS) microscopy is highly compact ultramicroscopy technique for imaging samples at nanoscales. It employs an electron point source (EPS) that produces a spatially-coherent low-energy spherical electron wave of 30-200 eV which passes through the sample and is partially scattered by the sample. Interference between the scattered and non-scattered wave leads to a hologram recorded at a distant detector. In the past two decades, LEEPS microscopy was used to achieve non-destructive imaging of individual DNA molecules, tobacco mosaic virions, individual proteins and protein complexes. However, the current LEEPS microscopy typically works in ultra-high-vacuum environment, and requires complex sample preparation steps and uses relatively rudimentary hologram processing methods, limiting its operational range and thus its potential deployment for in situ applications. In comparison, the hologram formation and reconstruction in LEEPS microscopy resembles those in digital inline holographic microscopy (DIHM), a popular 3D optical technique applied in a variety of in situ applications. The objective of our study is to develop a prototype system of LEEPS-DIHM for imaging nanoparticles (1-100 nm) by integrating advanced digital processing methods of DIHM with the concept of LEEPS microscopy. We will demonstrate the potential of this system for in situ imaging of nanoparticles produced in plasma reactors.
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