Carbon films obtained from fullerenes deposited on germanium: Experimental and simulated results

In this work, carbon thin films have been experimentally produced by accelerating ${\mathrm{C}}_{60}$ ions on germanium substrates at different deposition energies (from 50–$1000\mathrm{eV}$). Adherence and chemical composition have been studied in order to characterize the obtained material. On the other hand, molecular dynamics simulations have been used to investigate the microscopic processes of the growth of carbon thin films obtained from the collision of ${\mathrm{C}}_{60}$ molecules on germanium substrates. The Tersoff potential has been employed to describe the atomic interactions. Some properties of the films have been studied as a function of the deposition energy (from 10–$1000\mathrm{eV}$): interface thickness, density profile from the substrate up to the film surface, etc. Experimental and simulated results have been correlated to those obtained on silicon by similar methods. The results show that the structural and dynamical properties of the films depend on deposition energy, as it was observed on silicon substrates. For the studied energies, the simulated interface thickness is larger in germanium substrates than in silicon ones. However, experimentally observed adherence is poorer on germanium substrates.

Figure 1

Micrograph of delamination produced by buckling, observed in the surface of a sample deposited on Ge at $200\mathrm{eV}$ (100X).

Figure 2

(Color online) XPS spectra for the $\mathrm{C}1\mathrm{s}$ signals from samples deposited on Ge at $1000\mathrm{eV}$: experimental data (dots), fitting curves (solid lines).

Figure 3

(Color online) Calculated mean penetration depth of individual C atoms in $\mathrm{Ge}\left(100\right)$ substrates as a function of the deposition energy. Results calculated on diamond and silicon substrates are also shown.

Figure 4

(Color online) Snapshots of a ${\mathrm{C}}_{60}$ molecule thrown on diamond (100), $\mathrm{Si}\left(100\right)$, and $\mathrm{Ge}\left(100\right)$ substrates.

Figure 5

(Color online) Films grown throwing ${\mathrm{C}}_{60}$ molecules at 10, 300, and $1000\mathrm{eV}$ on $\mathrm{Si}\left(100\right)$ and $\mathrm{Ge}\left(100\right)$ substrates.

Figure 6

(Color online) (a) Density profiles of films deposited on $\mathrm{Ge}\left(100\right)$; (b) interface thickness as a function of ${\mathrm{E}}_{\mathrm{dep}}$.

Figure 7

(Color online) Number of $n$-coordinated atoms in as-grown and thermal annealed film: (a) carbon atoms; (b) germanium atoms.

Figure 8

(Color online) Density profiles of a film deposited at $1000\mathrm{eV}$ discriminating: (a) atomic species for as-grown and annealed $\left(1500\mathrm{K}\right)$ films; (b) three-, four-, five-, six-coordination for as-grown films; (c) three-, four-, five-, and six-coordination for annealed films $\left(1500\mathrm{K}\right)$.

Figure 9

(Color online) Angular distribution functions calculated taking angles with vertices at $s{p}^2$ C atoms, $s{p}^3$ C atoms, and Ge or Si atoms for films grown from ${\mathrm{C}}_{60}$ molecules deposited on $\mathrm{Ge}\left(100\right)$ and $\mathrm{Si}\left(100\right)$ substrates at 10 and $1000\mathrm{eV}$.