THE OPTICAL-ABSORPTION EDGE OF DIAMOND-LIKE CARBON - A QUANTUM-WELL MODEL

This article presents an analysis of the optical absorption edge of di amond-like carbon, based on transitions between confined electronic st ates in quantum wells. This theory is proposed to replace the commonly -used Tauc and Urbach expressions. It uses the cluster model of sample structure: the wells correspond to islands of graphitic, sp(2)-bonded material embedded in a diamond-like, sp(3)-bonded skeleton. A percola tion model is used to give the cluster size distribution. Near-edge op tical absorption coefficients are determined approximately for macrosc opic thin films that have low fractions of sp(2) bonding. Experimental results provide preliminary confirmation of the approach. (C) 1998 Am erican Institute of Physics. [S0021-8979(98)07202-8].