Extremely smooth (6 nm roughness) and continuous ultrananocrystalline diamond (UNCD) thin films were achieved by microwave plasma chemical vapor deposition using a thin 10 nm tungsten (W) interlayer between the silicon (Si) substrate and the diamond film. The W interlayer significantly increased the initial UNCD nucleation density to >10.sup.12 sites/cm.sup.2, thereby lowering the surface roughness and eliminating interfacial voids. A method is also disclosed to make various articles.
CONTRACTUAL ORIGIN OF THE INVENTION
 The United States Government has rights in this invention pursuant to Contract No. W-31-109-ENG-38 between the U.S. Department of Energy and The University of Chicago representing Argonne National Laboratory.