Measurement of lattice-fringe vectors from digital HREM images: experimental precision

The practical measurement of lattice-fringe spacings and angles recorded in digital high-resolution electron micrographs is evaluated experimentally. The method is based on a statistical estimation procedure and involves computer analysis of reciprocal-space parameters. This work concentrates on the analysis of images recorded with slow-scan CCD cameras, but alternative methods of image pick-up are also briefly considered. The method has been successfully applied to images recorded with electron doses smaller than 1eÅ2 and for sample dimensions as small as 8Åacross. The practical precision depends on specimen characteristics, electron dose and the size of the measurement area and is in the range of 0.001–0.05Åfor lattice spacings, and 0.1°–0.5° for lattice-plane angles. Finally, the technique is demonstrated in studies of a catalyst system, of a reduced surface oxide phase and of TiO2 and TiN particles.