Nanodiamond Closeups

from "Stardust in the TEM" inUltramicroscopy 27 (1989) 401-412

Above is a small version of Fig. 2b. The caption in the paper was "Darkfield images showing individual diamond crystallites in the Allende (a) and Murray (b) residues". Hence this is a darkfield image of nanodiamonds from the meteorite Murray. The contrast optimized 8-bit TIF image of this is just under 10 MB, and an 8 bit version of 2a and 2b together would be about twice that if that is preferable. Click on the numbers here for digitized versions of paper pages 401, 402, 403, 404, 405, 406, 407, 408, 409, 410, and 411.

A more descriptive caption for this 3.29 MB excerpt from Fig 2b might read: "Darkfield electron image of nanodiamonds from a dissolution residue of the meteorite Murray. Single crystals show up as bright dots only if their carbon-atom planes happen to be oriented so as to reflect electrons into the camera. Although a few of the nanodiamonds are 5 nm (25 atoms) across, most of them are under 1 nm (5 atoms) across. A few of the small ones have been circled." A reduced size version of this excerpt is shown below. Can you locate the five circled nanodiamonds?

Darkfield images (i.e. images formed without the unscattered beam) don't show lattice fringes which are created by interference between the diffracted beam (used to form darkfield images) and the "brightfield" or unscattered beam. Because of the juxtaposition of sub-nm diamonds in this material, it is difficult to see their lattice planes individually. However, lattice fringes for the larger crystals do show up well, as shown in the excerpt from Figure 12 below. A caption might read "Closeup of part of a 25 nm, possibly interstellar, shell of 2-4 nm diamonds (note the lattice fringes characteristic of diamond's very compact atomic lattice in the dark grains) in a field of much finer meteoritic nano-diamonds". Click here for a 2.4 MB version of this same excerpt. I will add a 3 nm scale bar to these images shortly.

Now on a more technical note, find in the top half of the image below closeup of the cross-fringe diamond crystal in Fig. 5 along with it's indexed diffraction pattern. Below find the result from Fig. 6: a rotated inset from the Fig. 5 image on the lower right, filtered to remove all except periodicities from the crystal giving the "diffraction spots" above, and then rotated and expanded for comparison with the model of carbon atoms in diamond viewed down the <110> direction on the left. A key element in interpreting the dark dots in the lower right image as carbon atom-columns is the "continuous contrast transfer cloud" in the upper right power spectrum which clearly shows no "zeros" (intensity phase inversions due to spherical abberation) between the central unscattered beam and the diffraction spots. Being able to do this for 2 Angstrom spacings, like those shown here, is basically what puts microscope price tags into the $1M and above range.