Application of the small-angle cleavage technique to thickness measurement of TEM samples.

In modelling transmission electron microscopy (TEM) images with the dynamical theory of electron diffraction, the sample thickness at the region of interest must be accurately known. A technique of sample preparation for cross-sectional single-crystal samples has been developed to provide this information. This technique, based on the small-angle cleavage technique, can allow a direct measurement of the sample thickness at the region where cross-sectional TEM analysis has been undertaken. Several cross-sectional samples of GaAs-based multiple quantum wells were prepared with parallel cleaved faces and thicknesses in the range of 50 to 200 nm. The samples were initially mounted so that cross-sectional images were obtained, then on suitable samples the mount was adjusted to obtain a plan view image of the same area. With suitable care, this technique provided an accurate thickness measurement of a cross-sectional region of a sample, which allowed subsequent modelling and analysis.