Raman spectroscopy study of the influence of processing conditions on the structure of polycrystalline diamond films

Abstract

Electrical conduction in undoped ultrananocrystalline diamond thin films and its dependence on chemical composition and crystalline structure Diamond films are prepared by microwave plasma-enhanced chemical-vapor deposition on Si ͑100͒ substrates using the H 2 -Ar-CH 4 gases. Raman scattering data, including the peak position, intensity, area, and width, are analyzed in depth and used to obtain the sp 3 -and sp 2 -bonded carbon contents and the nature of internal stresses in the films. Polarization behavior of the Raman peaks is analyzed to assess its role on the quantitative analysis of the diamond films, which suggested that the 1150 cm −1 Raman peak in nanocrystalline diamond films could be attributed to sp 2 -bonded carbon. The role of the H 2 / Ar content in the gas mixture and substrate temperature on the characteristics of the diamond film is studied. Thickness and grain size of diamond films are also determined by scanning electron microscopy and related to the deposition conditions and Raman results. Deposition conditions, which led to highest sp 3 -bonded carbon content and growth rate, are identified.

Effects of nanotopography on the in vitro hemocompatibility of nanocrystalline diamond coatings

“…Raman spectra confirmed the presence of sp 3 ‐hybridized carbon typical of diamond in both NCD coatings. The intensity of the 1332 cm −1 peak was significantly higher for the NCD‐L films compared to NCD‐S films; this finding is consistent with the literature for NCD films with larger grain sizes . Diamond films with columnar diamond grains of large grain sizes exhibit a lower density of grain boundaries and a lower sp 2 ‐hybridized carbon content …”

“…The intensity of the 1332 cm 21 peak was significantly higher for the NCD-L films compared to NCD-S films; this finding is consistent with the literature for NCD films with larger grain sizes. 53,54 Diamond films with columnar diamond grains of large grain sizes exhibit a lower density of grain boundaries and a lower sp 2 -hybridized carbon content. 55 The amount and orientation of the adsorbed proteins plays a critical role in the hemocompatibility of the device, as a higher ratio of albumin to fibrinogen (A:F) promotes lower platelet adhesion and reduces the tendency for thrombus formation.…”

Tribological investigation of nanocrystalline diamond films at low load under different tribosystems

“…[9,10] and other fields. Several research groups have been able to deposit nanocrystalline diamond films [10][11][12][13][14][15][16]. Developments of recent methods involve deposition of NCD films using relatively high carbon to hydrogen (C/H) ratio in microwave plasma and/or by applying DC bias to the substrate [17].…”

Microwave Permittivity of Trace sp2 Carbon Impurities in Sub-Micron Diamond Powders

“…The strong peak at approximately 1332 cm –1 is characteristic of the F 2g vibrational mode in sp 3 carbon, hence indicating a large volume fraction of diamond most commonly witnessed for microcrystalline diamond. 31,45 This peak may be obscured by additional D and G bands, associated with the aromatic A 1g breathing mode of disordered sp 2 carbon and the E 2g bond stretching of sp 2 carbon pairs, respectively, characteristic of graphitic carbon, 46 although in this instance, these bands are of minute intensity as compared to the diamond peak, as shown in Figure 3. Through linear extrapolation of a background baseline at higher wavenumbers, the inset in Figure 3 reveals a broad dispersion of bands around the diamond peak from 1320 to 1600 cm –1 , where the D and G bands would be present.…”

“…An indication of sp 2 /sp 3 carbon concentration from Raman is generally given through either the peak ratio of the G band and the diamond peak or a ratio of the integration of their respective areas. 45 Through observation, it is clear that the broad feature in Figure 3 inset between 1300 and 1600 cm –1 peaks at 1000 °C, however, the accuracy is heavily dependent upon the arbitrary classification of the Raman baseline level. For the sizes of the particles used here, they are much larger than those used in other annealing studies (5–50 nm range 28 ), and so the sp 2 growth rate is dramatically slower, producing a much smaller volume fraction of sp 2 carbon.…”