Molecular dynamics simulation of the growth of thin films by deposition of carbon atoms and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi mathvariant="normal">C</mml:mi><mml:mn>60</mml:mn></mml:msub></mml:math>molecules on diamond and silicon substrates

Abstract

The impact of C atoms and ${\mathrm{C}}_{60}$ molecules with ideal diamond and silicon (100) substrates and the subsequent growth of carbon films have been investigated by molecular dynamics simulations. The interatomic many-body potential proposed by Tersoff has been used. The structural and vibrational properties of the as-grown and annealed films are studied as a function of the deposition energy (in the range $1--150\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ for C atoms and $1--1000\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ for ${\mathrm{C}}_{60}$ molecules) and are compared with experimental results. Analysis of films grown from ${\mathrm{C}}_{60}$ molecules reveals a behavior with deposition energy similar to that experimentally observed. For low deposition energies (below $100\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$) fullerene cages preserve their identity, constructing low-density structures with large intermolecular holes and practically no interface with the substrate. For higher deposition energies the molecules are broken into pieces, giving as a result high-density amorphous carbon films. Although the penetration depth of molecular fragments into the substrate increases with deposition energy, the resulting interface is considerably thinner than in the case of using individual atoms as projectiles. This is in agreement with experimental evidence of a poor adherence of films obtained by accelerating $\mathrm{C}_{60}{}^{+}$ ions on silicon substrates.