The effect on spatial resolution of the spherical aberration of the objective prefield of a Philips CM30 (S)TEM has been investigated. For this purpose, the lattice mismatch of a 20 nm thick Si-Ge film in a cross-sectioned Si/Si0.9Ge0.1/Si heterostructure has been determined by convergent beam electron diffraction (CBED), performed at 100 kV with a spot size of 20 nm. It has been found that, if the disk of minimum confusion is focused onto the specimen plane: the measurement is not affected by a change in the size of the condenser-2 aperture. Therefore, the mismatch information is contained within the Gaussian part of the electron probe. In strain profile determinations by CBED, this allows one to use higher beam intensities (larger C2-apertures) with improved signal/noise ratios and reduced sample drift due to shorter acquisition times.
On the spatial resolution in analytical electron microscopy / Armigliato, A; Howard, Dj; Balboni, R; Frabboni, Stefano; Caymax, Mr. - In: MIKROCHIMICA ACTA. - ISSN 0026-3672. - STAMPA. - 15:(1998), pp. 59-64.
On the spatial resolution in analytical electron microscopy
FRABBONI, Stefano;
1998
Abstract
The effect on spatial resolution of the spherical aberration of the objective prefield of a Philips CM30 (S)TEM has been investigated. For this purpose, the lattice mismatch of a 20 nm thick Si-Ge film in a cross-sectioned Si/Si0.9Ge0.1/Si heterostructure has been determined by convergent beam electron diffraction (CBED), performed at 100 kV with a spot size of 20 nm. It has been found that, if the disk of minimum confusion is focused onto the specimen plane: the measurement is not affected by a change in the size of the condenser-2 aperture. Therefore, the mismatch information is contained within the Gaussian part of the electron probe. In strain profile determinations by CBED, this allows one to use higher beam intensities (larger C2-apertures) with improved signal/noise ratios and reduced sample drift due to shorter acquisition times.
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