QUANTITATIVE COMPARISON OF TEM TECHNIQUES FOR DETERMINING AMORPHOUS INTERGRANULAR FILM THICKNESS

The question of which transmission electron microscopy technique can best be used to quantitatively determine the thickness of thin intergranular films is addressed. Measurement of the film thickness by diffuse dark-field imaging resulted in values 50% to 100% larger than those determined by high-resolution lattice imaging. Defocus Fresnel fringe imaging is an indirect method of obtaining intergranular film thickness; with this method thicknesses were over-estimated by 20% to 35%, with the largest error caused by uncertainty in the exact location of fringe maxima. Although technically difficult to use, high-resolution lattice imaging is a method capable of the resolution necessary to obtain detailed information of the boundary and the intergranular phase itself; it was found to be the most applicable to quantitative measurements of film thicknesses in Si3N4 materials, with an accuracy of +/- 1 angstrom (+/- 0.1 nm).