Nanoparticle structure from focal-series reconstruction of the specimen exit-surface electron wave with sub-Angstrom electron microscopy
The one-Angstrom microscope (O Angstrom M) project exceeds the 1.7 Angstrom Scherzer resolution of a mid-voltage TEM to reach better than one-Angstrom at 300keV by combining a modified CM300FEG-UT with computer software able to correct Cs and generate sub-Angstrom images from experimental image series. The O Angstrom M has demonstrated that a resolution of 0.78 Angstrom is possible with this technique. The O Angstrom M was designed to use focal-series reconstruction to achieve sub-Angstrom resolution in order to allow imaging atom positions in non-periodic structures such as defects in crystalline specimens, and severely non-periodic specimens such as nanoparticles with their strong Fresnel fringes. As a test of the technique, we have used the O AngstromM to produce an image of the exit-surface wave (ESW) of a 70 Angstrom particle of gold supported on amorphous carbon by applying focal-series reconstruction (FSR) to a series of 20 images obtained at focus values ranging from -2600 Angstrom to -2144 Angstrom. The phase of the complex ESW shows the positions of the atom columns in the specimen as white dots, clearly demonstrating five-fold twinning that is not visible in the Scherzer image at a resolution of 1.7 angstrom.