Regensburg 2013 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 70: Poster Session: Devices; Preparation and characterization; C/diamond; Si/Ge

HL 70.11: Poster

Mittwoch, 13. März 2013, 16:00–20:00, Poster A

Simulated annealing of nanodiamonds in vaccum, oxygen and water vapor — •Moloud Kaviani, Peter Deák, Bálint Aradi, and Thomas Frauenheim — BCCMS University of Bremen TAB Building, Entrance 1 A, Level 3 The case of Tower 1 28359 Bremen

Biocompatible luminescent nanodiamonds (ND) have received considerable attention as markers in biophysics and nanomedicine. For these applications NDs should be produced as small as possible. Transmission electron microscopy studies have shown that NDs are polyhedra with a diamond core, partly covered by a shell of graphitic or amorphous carbon. Our goal is to estimate how small can NDs be to preserve the diamond core at elevated temperatures under various ambient conditions: in vacuum, in oxygen, and water vapor. We investigate the stability of diamond nanoparticles upon annealing as a function of the size and shape, with the help of molecular dynamics (MD) simulations, using the self-consistent density functional based tight-binding method (SCC-DFTB). Simulated isochronal annealing was carried out at 500K, 1000K, 1500K for 30ps with a linear ramp between the stages (for 10ps).The diamond core of cuboid and cuboctahedral clusters with as like as ~250 atoms survives such short anneals. As accelerated MD at 5000K, as well as tests at 1500K for 250 ps indicate that they are likely to survive also longer annealing times. The primary effect of oxygen seems to be saturated threefold-coordinated surface carbon atoms and the etching of coordinated ones.The application process becomes somewhat quicker and stronger but about a ~250 atom cluster still retains its diamond core in the longer run.