Structural and optical properties of diamond and nano-diamond films grown by microwave plasma chemical vapor deposition

• Published in: Diamond and related materials Vol. 10; no. 3; pp. 561 - 567
• Main Authors: Sharda, T., Rahaman, M.M., Nukaya, Y., Soga, T., Jimbo, T., Umeno, M.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01-03-2001; Elsevier
• Subjects: Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Microcrystalline diamond; Nanocrystalline diamond; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of specific thin films; Other semiconductors; Physics; Plasma chemical vapor deposition; Solid surfaces and solid-solid interfaces; Surface structure and topography; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Nanocrystalline diamond; Microcrystalline diamond; Plasma chemical vapor deposition; Raman spectra; Synthetic mineral; Microwave radiation; Diamonds; Roughness; Surfaces; Crystal growth from vapors; Infrared spectra; Experimental study; Characterization; Thin films; CVD; Nonmetals; Ultraviolet visible spectrum; PECVD; Microcrystal; Optical coatings; Optical constants; Nanocrystal
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/S0925-9635(00)00390-3

We compare structural and optical properties of microcrystalline and nanocrystalline diamond (MCD and NCD, respectively) films grown on mirror polished Si(100) substrates by microwave plasma chemical vapor deposition. The films were characterized by SEM, Raman spectroscopy, XRD, and AFM. Optical properties were obtained from transmittance and reflectance measurements of the samples in the wavelength range of 200–2000 nm. Raman spectrum of the MCD film exhibits a strong and sharp peak near 1335 cm
−1, an unambiguous signature of cubic crystalline diamond with weak non-diamond carbon bands. Along with broad non-diamond carbon bands, Raman spectra of NCD films show features near 1140 cm
−1, the intensity of which is significantly higher in the film grown at 600°C compared to the NCD film grown at higher temperature. The Raman feature near 1140 cm
−1 is related to the calculated phonon density of states of diamond and has been assigned to nanocrystalline or amorphous phase of diamond. XRD patterns of the MCD film show sharp peaks and NCD films show broad features, corresponding to cubic diamond. The rms surface roughness of the films was observed to be approximately 60 nm for MCD film that reduced substantially to 17 and 34 nm in the NCD films grown at 600 and 700°C, respectively. Tauc's optical gap for the diamond film is found to be approximately 5.5 eV. NCD grown at 700°C has a high optical absorption coefficient in the whole spectral region and the NCD film grown at 600°C shows very high transmittance (∼78%) in the near IR region, which is close to that of diamond. This indicates that the NCD film grown at 600°C has the potential for applications as optical windows since its surface roughness is significantly low as compared to the MCD film.