: The effectiveness of applying a high-frequency, low-energy, reactive gas plasma for the removal of hydrocarbon contamination from specimens and components for electron microscopy has been investigated with a variety of analytical techniques. Transmission electron microscopy (TEM) analysis of specimens that have been plasma cleaned shows an elimination of the carbonaceous contamination from the specimen. With extended cleaning times the removal of existing carbon contamination debris due to previously conducted microanalysis is shown. Following plasma cleaning, specimens may be examined in the electron microscope for several hours without exhibiting evidence of recontamination. The effectiveness of plasma cleaning is not limited to applications for TEM specimens. Scanning electron microscopy (SEM) specimens that have been plasma cleaned likewise show an elimination of carbonaceous contamination. Furthermore, other electron microscopy parts and accessories, such as aperture strips, specimen clamping rings, and Wehnelts, among others, can benefit from plasma cleaning.

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The advent of aberration correction for transmission electron microscopy has transformed atomic resolution imaging into a nearly routine technique for structural analysis. Now an emerging frontier in electron microscopy is the development of in situ capabilities to observe reactions at atomic resolution in real-time and within realistic environments. Here we present a new in situ gas holder that was designed to bypass several limitations that have plagued previous in situ gas holders. The new holder is compatible with any type of sample, and its capabilities include localized heating and precise control of the gas pressure and composition while simultaneously allowing atomic resolution imaging at ambient pressure. The results show that 0.25 nm lattice fringes are directly visible for nanoparticles imaged at ambient pressure with gas path lengths up to 20 µm. Additionally, we quantitatively demonstrate that while the attainable contrast and resolution decrease with increasing pressure and gas path length, resolutions better than 0.2 nm should be accessible at ambient pressure with gas path lengths less than the 15 µm utilized for these experiments. 3The ability to study gas-solid interactions with atomic resolution and ambient pressures in the transmission electron microscope (TEM) promises new insights into the growth, properties, and functionality of nanomaterials. Heterogeneous catalysis is a particular application in which, the structure, morphology, and chemistry of nanoparticles are dynamic and greatly depend on the gas environment and temperature [1][2][3][4][5][6][7] . Unfortunately, conventional high-resolution TEM of catalysis is extremely challenging since both ambient pressure and elevated temperature can adversely affect imaging conditions. This is further complicated by the fact that normal TEM imaging is performed under a high vacuum (1.5x10 -7 Torr) to prevent unwanted scattering from gases. Therefore, to enable in situ experiments within the column of an electron microscope, a localized gas environmental chamber with controllable gas pressure, composition, and temperature is crucial. Such conditions can be obtained using an environmental cell built around the specimen.The original designs for environmental cells have been around for over 70 years 8 and are produced by either incorporating differentially pumped apertures that separate the specimen from the high vacuum of the TEM column 1, 9-16 or windowed-cell designs that confine the gas within the specimen holder using electron-transparent membranes 4,10,[17][18][19][20][21][22] . Atomic-resolution images in gaseous environments have been obtained with both techniques at pressures up to ~10 Torr 1,5,15,22,23 , but the technological relevance of these measurements may not be compatible with the more realistic operating conditions of catalyst nanomaterials at higher pressures. Environmental transmission electron microscopes (ETEM) that incorporate differentially pumped apertures are generally limited to pressures of 15-20 Torr but they per...

With the recent advances made in monochromation of electron sources and Cs-correction, the point resolution of the transmission electron microscope (TEM) has been extended into the sub-Angstrom regime. This development has led to an important consequence—that specimen preparation has become a more critical issue for the materials scientist. Nanoscale artifacts that could be tolerated a few years ago when imaging in the 0.1–0.15 nm range can no longer be allowed. An example is hydrocarbon contamination, which although only a few monolayers thick, obscures the area of interest. Other examples include residual deformation and oxidation following traditional mechanical methods. Ion-based methods may induce amorphization and implantation defects, depending on the type of ion, its energy, and the particular protocol that is used.

This paper reports on the substantial improvement of specimen quality by use of a low voltage (0.05 to~1 keV), small diameter (~1 μm), argon ion beam following initial preparation using conventional broad-beam ion milling or focused ion beam. The specimens show significant reductions in the amorphous layer thickness and implanted artifacts. The targeted ion milling controls the specimen thickness according to the needs of advanced aberration-corrected and/or analytical transmission electron microscopy applications.