Lognormal mass distributions of nanodiamonds from proportionate vapor growth

For the investigation of the statistical growth behavior of diamond nanoparticles in vapor phase, a direct mass distribution determination was performed using laser ablation/ionization mass spectrometry. Different types of samples were investigated: cosmic diamonds of presolar origin found in meteorites, and larger synthetic diamonds obtained from vapor detonation processes. All samples exhibit lognormal mass distributions which are indicative for size-dependant (i.e., proportionate) molecular growth similar to chemical vapor depositionlike processes. The distribution parameters are extracted and discussed against the background of the statistical theory.

Figure 1

TEM images obtained from three types of nanodiamond samples. (a) and (b): enlarged views of a selected Murchison (a) and Allende (b) meteorite diamonds, showing the characteristic lattice planes of $0.21\mathrm{nm}$ distance; (c) enlarged view of an individual synthetic diamond (UDD sample). (a) was provided by F. Banhart, (b) and (c) by P. van Aken.

Figure 2

Laser ablation/ionization time-of-flight mass spectra from the different nanodiamond samples: (a) Murchison, (b) Allende, and (c) synthetic diamonds. Each spectrum clearly exhibits a significantly asymmetric shape, as it is typical for lognormal size distributions.

Figure 3

(Color online) Probability plots extracted from the nanodiamond mass spectra from Fig. 2. Each point averages 10 data points from the mass spectrum. Straight lines are inserted for the emphasis of lognormal behavior within the major part of the cumulative axis. Deviations mainly towards higher masses are discussed in the text.