A new method for the determination of the wave aberration function for high resolution TEM: 1. Measurement of the symmetric aberrations

• Published in: Ultramicroscopy Vol. 92; no. 2; pp. 89 - 109
• Main Authors: Meyer, R.R, Kirkland, A.I, Saxton, W.O
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.07.2002; Elsevier Science
• Subjects: Electron, positron and ion microscopes, electron diffractometers and related techniques; Exact sciences and technology; High resolution electron microscopy; Image restoration; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Physics; Wave aberration function; High resolution electron microscopy; 07.05; Image restoration; Wave aberration function; 07.78; Automation; Inorganic compounds; Image processing; Ternary compounds; Theoretical study; Tungsten oxides; Experimental study; Correlation functions; High-resolution methods; Image reconstruction; Transmission electron microscopy; Aberrations; Niobium oxides
• ISSN: 0304-3991; 1879-2723
• DOI: 10.1016/S0304-3991(02)00071-2

A new method for the accurate determination of the symmetric coefficients of the wave aberration function has been developed. The relative defoci and displacements of images in a focus series are determined from an analysis of the phase correlation function between pairs of images, allowing the restoration of an image wave even when focus and specimen drift are present. Subsequently, the absolute coefficients of both defocus and 2-fold astigmatism are determined with a phase contrast index function. Overall this method allows a very accurate automated aberration determination even for largely crystalline samples with little amorphous contamination. Using experimental images of the complex oxide Nb 16W 18O 94 we have demonstrated the new method and critically compared it with existing diffractogram based aberration determinations. A series of protocols for practical implementation is also given together with a detailed analysis of the accuracy achieved. Finally a focal series restoration of Nb 16W 18O 94 with symmetric aberrations determined automatically using this method is presented.