Elastic, mechanical, and thermal properties of nanocrystalline diamond films

Abstract

Nanocrystalline columnar-structured diamond films with column diameters less than 100 nm and thicknesses in the range of 1-5 m were grown on silicon substrates by chemical vapor deposition ͑CVD͒ in a microwave plasma reactor with purified methane and hydrogen used as the reactants. Uniform conformal nucleation densities in excess of 10 12 cm Ϫ2 were accomplished prior to growth by seeding with explosively formed nanodiamonds, which resulted in good optical quality films. The film thickness was measured in situ by the laser reflectometry method. The grain size and optical quality of the films were characterized by scanning electron microscopy and Raman measurements. Broadband surface acoustic wave pulses were used to measure the anomalous dispersion in the layered systems. The experimental dispersion curves were fitted by theory, assuming the diamond film as an isotropic layer on an anisotropic silicon substrate, to determine mean values of the density and Young's modulus of the diamond films. The density was close to the density of single crystal diamond or polycrystalline diamond plates grown by the CVD technique, whereas the Young's modulus varied strongly with the nucleation density between 517 and 1120 GPa. Young's moduli close to the single crystal values were obtained for films grown with a nucleation density у10 12 cm Ϫ2. The thermal diffusivity in these films was measured by the traveling wave technique. The value for ϳ3.5-m-thick nanocrystalline diamond films with nucleation densities у10 12 cm Ϫ2 was ϳ7.2 cm 2 /s, whereas those with lower nucleation densities showed a value of ϳ5.5 cm 2 /s.

Diamond growth by chemical vapour deposition

“…These films show enormous stress, ranging from 1GPa to 85GPa; apparently, the combination of surface and sub-plantation processes leads to the formation of a mixed phase containing amorphous tetrahedral carbon and NCD, originating the high internal stress. Deposition under extremely low (0.3%) CH 4 /H 2 ratios originates the highest quality NCD films, with a low content of non-sp 3 carbon and high Young's modulus, thermal diffusivity and nucleation density [152]. Fig.…”

Optical properties of heavily boron-doped nanocrystalline diamond films studied by spectroscopic ellipsometry

“…As such films can be deposited on a plethora of materials, 1 possible applications include NEMS and MEMS structures, 2 biosensors, 3 tribology, 4 optical coatings 5 and thermal management. 6 By adding boron, NCD films can be turned into a p-type semiconductor. Conductivity values can be tuned within 11 orders of magnitude, with values ranging between 1 x10 -9 Ω-1 cm -1 and 100 Ω -1 cm -1 .…”

Nanomechanical resonant structures in nanocrystalline diamond

“…The deposition is done by microwave plasma enhanced chemical vapor deposition ͑CVD͒ using CH 4 and H 2 . 13,14 The substrate is pretreated by exposing it to the deposition conditions in the microwave chamber for 20 min.…”