{'fraction_non_alphanumeric': 0.04015056461731493, 'fraction_numerical': 0.010037641154328732, 'mean_word_length': 4.891625615763547, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Fluctuation Electron Microscopy on a-Ge and Polycrystalline Gold

Structural information from amorphous materials is more difficult to obtain than from crystalline ones, and the methods are mainly restricted to scattering experiments with photons, neutrons or electrons. The scattered intensity is used to calculate the pair distribution function (PDF), which is a two-body function g2(r) representing the difference between the averaged local atomic density measured from an arbitrary atom and the macroscopic density of the material. The information obtained is predominantly on the short-range order (SRO) of the material. Treacy and Gibson [1,2] proposed a new method, named “fluctuation electron microscopy, FEM”, to measure higher-order distribution functions, involving three or four atom correlations. With this method it should be possible to obtain information on the medium-range order (MRO), which gave us motivation to apply and test the FEM. In this contribution we present FEM-studies on amorphous germanium (a-Ge) and polycrystalline gold (Au). Our results are based on dark field images produced with hollow cone illumination (HCDF) using a Philips CM30ST operated at 200 kV. As fluctuations of the image intensity depending on the cone angle were measured, we used “variable coherence microscopy” [1] as one kind of FEM. After careful alignment of the beam (pivot points, roundness, focus, etc.) image series were acquired under remote control of the electron microscope at magnifications of 3.25 Å/pixel (aGe), resp. 5.82 Å/pixel (Au) on a 1k CCD-camera (Gatan MSC794). The images were extensively processed in order to obtain the true electron intensity and to remove unwanted contributions to the variance, which includes gain-normalization, removal of X-rays, MTF-deconvolution and low pass filtering. To achieve statistically significant data, the images are divided into 9 equally-sized subimages, from which the mean intensity (I) and the variance (v) of the intensity were determined. Sub-images showing an extremely large deviation in v compared to the mean v value of all subimages pertaining to the same cone angle were not considered for analysis. Examples for high (a) and low (b) variance HCDF-images of both Au and a-Ge are shown in Fig.1 and Fig.3. The variance v as well as the mean intensity I as a function of the cone angle are shown in Fig.2 and Fig.4.