Paper TF2-ThA8
Synthesis and Theoretical Modeling of Fullerene-like Phospho-Carbide Compounds

Thursday, October 18, 2007, 4:20 pm, Room 613/614

First-principles DFT calculations predict that Fullerene-like (FL) CPx compounds can have resilient mechanical behavior similar to FL-CNx, but for a lower V element concentration. P is a higher period element compared to N. This means a higher freedom with respect to chemical bonding which is likely to affect the structure of the CPx compounds compared to FL-CNx. The results of theoretical simulation of synthetic growth of FL-CPx structures show that the substitution of N with P makes the formation of tetragon defects energetically favorable and that P-P bonds are plausible. This implies stronger curvature and interlocking of graphene planes. Concurrent inter- and cross-linking of the bent graphene planes induced by the P atom leads to cage- and onion-like structures which promise improved mechanical properties of the FL solids. In this paper we also present results from magnetron sputtering deposition of CPx thin films. The films were deposited by DC magnetron sputtering in Ar atmosphere from a compound graphite-P target containing between 5 and 15 at.% of P. Higher proportions of P in the target should be avoided since P-rich species in the deposition flux might result in P-segregation during film growth. The substrates were Si and NaCl wafers kept at a bias voltage in the range of -20 V to -50 V, and substrate temperature ranging from 150 ^oC to 780 ^oC. As-deposited coatings were analyzed using XPS, nanoindentation, SEM, and TEM. The preliminary results show that incorporation of P into the film is promoted at lower substrate temperatures and higher bias voltages. Nanoindentation experiments show that resistance to indentation and hardness of the CPx increases for decreasing substrate temperature and increasing bias voltage.