Atom‐probe analyses of nanodiamonds from Allende

Abstract

Abstract-Atom-probe tomography (APT) is currently the only analytical technique that, due to its spatial resolution and detection efficiency, has the potential to measure the carbon isotope ratios of individual nanodiamonds. We describe three different sample preparation protocols that we developed for the APT analysis of meteoritic nanodiamonds at sub-nm resolution and present carbon isotope peak ratios of meteoritic and synthetic nanodiamonds. The results demonstrate an instrumental bias associated with APT that needs to be quantified and corrected to obtain accurate isotope ratios. After this correction is applied, this technique should allow determination of the distribution of 12 C/ 13 C ratios in individual diamond grains, solving the decades-old question of the origin of meteoritic nanodiamonds: what fraction, if any, formed in the solar system and in presolar environments? Furthermore, APT could help us identify the stellar sources of any presolar nanodiamonds that are detected.

C12/C13Lewis1, Isheim2, Floss3 et al. 2015UltramicroscopySelf Cite310120View full textAdd to dashboardCite

“…The systematic error that lowers our measured standard ratios from the terrestrial value, effect (1), is also present in microtips produced by [4], but effect (2) is not consistently reproduced. Heck et al use two additional sample preparation techniques, one with nanodiamonds in a horizontal layer through the microtip on top of Si, covered in cobalt, the other with nanodiamonds on the exterior of a presharpened Si micropost.…”

“…Table 1 summarizes these data. Of these, 9 DND and 3 ADM datasets were originally reported in [4] and are presented here with new ROI selections and deadtime corrections. We exclude data collected prior to the most recent major hardware upgrade to the atom-probe tomograph, which is described in [4].…”

“…In light of this limitation, we have been analyzing meteoritic nanodiamonds and terrestrial nanodiamond standards using atom-probe tomography (APT) [4][5][6]. Our scientific goal is to determine the origins of the nanodiamonds by determining what, if any, anomalies exist in the C isotopes of the nanodiamonds.…”

“…A## M## indicates the microtip analyzed. Datasets previously included in[4], here presented with updated ROIs and deadtime corrections. c Too few multi-hits to deadtime correct.…”

Correlative Transmission Electron Microscopy and Atom-Probe Tomography of an Iron Meteorite

“…Correlated TEM/APT studies are state of the art in material science [3]. In our effort to broaden the application of APT in cosmochemistry [4], we expand our range of projects from meteoritic nanodiamonds [5] and presolar silicon carbide [6,7] to other samples. Here, we present new data from a correlated TEM/APT study of an iron meteorite [8].…”