Near- and far-field Raman spectroscopic studies of nanodiamond composite films deposited by coaxial arc plasma

Abstract

Raman spectroscopic studies on nanodiamond composite (NDC) films, comprising nano-sized diamond grains and an amorphous carbon (a-C) matrix, deposited by coaxial arc plasma deposition are challenging because the scattering of the nano-sized diamond grains competes with the strong signal of the a-C matrix. To unravel the nanocomposite structure of NDC films, both far- and near-field Raman spectroscopy were employed. Based on the comparison of visible and ultraviolet far-field Raman data, component spectra based on either nanodiamond or a-C were estimated by a peak-decomposition procedure based on band fitting. Near-field optical resolution achieved via tip-enhanced Raman spectroscopy reveals sharper peaks of both the nanodiamond and the amorphous carbon than the far-field spectra. Consequently, the peak-decomposition procedure is not required, which evidently indicates the effective detection of nanodiamond grains embedded in a-C matrices and is a direct result of the high spatial resolution that limits the number of probed grains. The size of the nanocrystals could additionally be estimated from the profile and position of a diamond peak. This work demonstrates that tip-enhanced Raman spectroscopy is a powerful nondestructive method for nanodiamond composite films, which allows direct access to parameters hitherto only available via average data.

Low-stress diamond-like carbon films containing carbon nanoparticles fabricated by combining rf sputtering and plasma chemical vapor deposition

“…Therefore, the incorporation of CNPs barely changes the structure of DLC films. 26) The compressive stress of DLC films arises from the atomic peening mechanism during the sputtering process. [27][28][29] Although the stress reduction mechanism due to the CNP layer has not yet been identified, there are three possible mechanisms.…”

Maximizing visible Raman resolution of nanodiamond grains fabricated by coaxial arc plasma deposition through oxygen plasma etching optimization

“…The presence of nanodiamond grains is already authenticated using tip-enhanced Raman spectroscopy in our previous work. 15 F I G U R E 1 Schematic representation of coaxial arc plasma deposition apparatus.…”

“…In addition, limited employment of visible Raman spectroscopy for nanodiamond signature distinction has been reported in recent years. 9,15 A qualitative Raman distinction of the nanodiamond signature from UNCD/a-C composite film fabricated by CAPD demands prior surface treatments and spectroscopic accompaniments like ultraviolet excitation wavelengths and near-field focusing. 15 The aforementioned limitations of visible light excitation of CAPD nanodiamonds are predominantly due to their amalgamation with the complex amorphous carbon matrix, resulting in effective resonance between the vibrational energy levels of the graphitic carbon matrix and the visible radiation.…”

“…9,15 A qualitative Raman distinction of the nanodiamond signature from UNCD/a-C composite film fabricated by CAPD demands prior surface treatments and spectroscopic accompaniments like ultraviolet excitation wavelengths and near-field focusing. 15 The aforementioned limitations of visible light excitation of CAPD nanodiamonds are predominantly due to their amalgamation with the complex amorphous carbon matrix, resulting in effective resonance between the vibrational energy levels of the graphitic carbon matrix and the visible radiation. Owing to the small grain size and large Raman cross section of the sp 2 -hybridized carbon in visible ranges, the effectual visible excitation of nanodiamond particles in UNCD/a-C composite film fabricated by CAPD needs the optimum removal of the sp 2 carbon matrix surrounding the UNCD grains and agglomerations.…”

Influence of adhesion intermediate layers on the stability of nanodiamond composite films deposited on Si substrates by coaxial arc plasma

“…For details on the TERS study on NDC films it is referred to our previous study. 27) The hardness of 55 GPa is attributed to a high nanodiamond content and a large sp 3 contribution, which were detected in the tip-enhanced Raman and X-ray photoemission spectra.…”