Abrupt Stress Induced Transformation in Amorphous Carbon Films with a Highly Conductive Transition Phase

D. W. M. Lau, D. G. McCulloch, M. B. Taylor, J. G. Partridge, D. R. McKenzie, N. A. Marks, E. H. T. Teo, and B. K. Tay

Phys. Rev. Lett. 100, 176101 – Published 28 April 2008

Abstract

We demonstrate that when, and only when, the biaxial stress is increased above a critical value of $6 \pm 1 GPa$ during the growth of a carbon film at room temperature, tetrahedral amorphous carbon is formed. This confirms that the stress present during the formation of an amorphous carbon film determines its $s p^{3}$ bonding fraction. In the vicinity of the critical stress, a highly oriented graphitelike material is formed which exhibits low electrical resistance and provides Ohmic contacts to silicon. Atomistic simulations reveal that the structural transitions are thermodynamically driven and not the result of dynamical effects.