Surface electronic density of states of tetrahedral amorphous carbon investigated by scanning tunneling spectroscopy and ab initio calculations

The surface electronic density of states of tetrahedral amorphous carbon ha s been measured by scanning tunneling microscopy and calculated by density functional theory. An analysis of these results and their comparison is pre sented here for a series of structures with different microscopic mass dens ities. The experimental structures were obtained by pulsed laser deposition with varying conditions resulting in diamond-like carbon thin films. The c alculated carbon structures were generated by simulating a melting-cooling cycle with molecular dynamics using the density functional energetics withi n the local density approximation. The experimental and calculated densitie s of states show good agreement. Graphitic-like surface reconstruction is b oth observed at the sp(3)-rich tetrahedral amorphous carbon (ta-C) sample a nd found in the calculated ta-C slab structure. (C) 2000 American Institute of Physics. [S0003-6951(00)01719-8].