Abstract
AbstractScanning transmission electron microscopy (STEM) provides sub-ångstrom, atomic resolution images of crystalline structures. However, in many applications, the ability to extract information such as atom positions, from such electron micrographs, is severely obstructed by low signal-to-noise ratios of the acquired images resulting from necessary limitations to the electron dose. We present a denoising strategy tailored to the special features of atomic-resolution electron micrographs of crystals limited by Poisson noise based on the block-matching and 3D-filtering (BM3D) algorithm by Dabov et al. We also present an economized block-matching strategy that exploits the periodic structure of the observed crystals. On simulated single-shot STEM images of inorganic materials, with incident electron doses below 4 C/cm 2, our new method achieves precisions of 7 to 15 pm and an increase in peak signal-to-noise ratio (PSNR) of 15 to 20 dB compared to noisy images and 2 to 4 dB compared to images denoised with the original BM3D.
Highlights
Modern electron microscopy allows for atomic resolution images of crystalline structures [1]
While we focus on the application of scanning transmission electron microscopy (STEM) imaging of inorganic materials, the key features of Poisson noise and oversampling are shared by high-resolution transmission electron microscopy (HRTEM) images as well, so the proposed method should be applicable to HRTEM images
Note that we define nUaggr in analogy to (23) but withx replaced by Results and discussion We have presented several modifications of the original block-matching and 3D-filtering (BM3D) filter as it was proposed by Dabov et al [24], including the extension to Poisson noise removal due to Mäkitalo and Foi [26]
Summary
Modern electron microscopy allows for atomic resolution images of crystalline structures [1]. The full scope of resolution can be exploited only for materials with little electron beam sensitivity. Lowering the electron dose decreases the signal-to-noise ratio (SNR) of the acquired micrographs degrading the quality or even completely prohibiting the extraction of desired information from the noisy micrographs. Examples of inorganic materials with high beam sensitivity, where scanning transmission electron microscopy (STEM) images of poor SNR have to be used, are both oxide [2] and metallic [3] catalysts. One important quantity that may be extracted from atomic-resolution electron micrographs is the positions of the atoms. The precision with which these can be determined is crucial for the understanding of certain material properties [4,5].
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