Spectroscopic ellipsometry characterization of nano-crystalline diamond films prepared at various substrate temperatures and pulsed plasma frequencies using microwave plasma enhanced chemical vapor deposition apparatus with linear antenna delivery

Spectroscopic Ellipsometry of Nanocrystalline Diamond Film Growth

“…32,7 For thicker NCD films modeled with a seed layer to account for the inferior diamond present at the interface with the substrate, similar thicknesses of 15–41 nm are reported. 24,26…”

“…In the present study, however, SE estimates an initial seed layer composed of 55% void dropping to 33% upon 4 min of growth and the formation of aggregated less ordered nuclei. Therefore, with the high packing density of the 4–8 nm DND seeds demonstrated by the low vertical displacement in Figure b reminiscent of that demonstrated by Hees et al and the previously reported stability of seeds under H 2 plasma conditions, it is likely that the nucleation density is of the order of 10 11 cm –2 . , For thicker NCD films modeled with a seed layer to account for the inferior diamond present at the interface with the substrate, similar thicknesses of 15–41 nm are reported. , …”

“…32,7 For thicker NCD films modeled with a seed layer to account for the inferior diamond present at the interface with the substrate, similar thicknesses of 15−41 nm are reported. 24,26 The fitted surface roughness EMA thickness and the AFM RMS roughness obtained through the averaging of 1 and 25 μm 2 scans for the 4−40 and 123 min growth duration samples, respectively, are plotted in the second panel of Figure 8. Due to the nature of the effective medium approximation, SE is most sensitive to roughness between the atomic scale and a tenth of the wavelength of the probing light, 27 with finite element method simulations showing the breakdown of the approximation as the roughness increases.…”

“…19,20,26−28 Although “seed” layers of 15–41 nm adjacent to the substrate rich in sp 2 , void, and occasionally SiC content have been observed with such an approach, 20,24,25 parameter correlation with the impurity fractions within the bulk prevents determination of the microstructure of this layer with any confidence. 26 More comprehensively, in situ characterization of the initial stages of diamond growth atop diamond grit-abraded silicon substrates modeled the transition from isolated islands to coalesced film. 21,29−31 During these studies, the authors noted an initial parabolic reduction in the void content, indicative of lateral VW-type growth, followed by coalescence and a sharp peak in the sp 2 fraction indicative of the trapping of nondiamond material within the grain boundaries, 21,29 accentuated by the large surface/volume ratio of crystallites.…”

“…Previous attempts at SE characterization of bulk nanocrystalline and microcrystalline diamond films have predominantly focused on the use of a Bruggeman effective medium approximation (EMA) to mix reference optical indices of the expected constituents and represent the film by a single homogenous medium, − successfully showing incremental improvements in fit upon the addition of components to represent grain boundary sp 2 carbon and void content between the nuclei, and surface roughness. ,,− Although “seed” layers of 15–41 nm adjacent to the substrate rich in sp 2 , void, and occasionally SiC content have been observed with such an approach, ,, parameter correlation with the impurity fractions within the bulk prevents determination of the microstructure of this layer with any confidence . More comprehensively, in situ characterization of the initial stages of diamond growth atop diamond grit-abraded silicon substrates modeled the transition from isolated islands to coalesced film. ,− During these studies, the authors noted an initial parabolic reduction in the void content, indicative of lateral VW-type growth, followed by coalescence and a sharp peak in the sp 2 fraction indicative of the trapping of nondiamond material within the grain boundaries, , accentuated by the large surface/volume ratio of crystallites.…”