Characterizations of microwave plasma CVD grown polycrystalline diamond coatings for advanced technological applications

Abstract

Polycrystalline diamond (PCD) coatings ranging from few microns to several hundred microns thickness have been grown by 915MHz microwave plasma reactor with 9000W power. The coatings were deposited on 100mm diameter silicon (Si) substrate from few hours to several days of continuous runs. PCD coatings were made freestanding by wet chemical etching technique. The deposited PCDs were evaluated by X-ray diffraction (XRD), scanning electronmicroscopy (SEM), Raman spectroscopy,X-ray photoelectron spectroscopy (XPS) for physical characterization and compared with authors? earlier work. Refractive index of 2.41 was obtained at 633 nm wavelength and a maximum of 6.6 W?cm-1K-1 value for thermal conductivity could be achieved with the grown coatings. The values are well above the existing non-diamond heat spreading substrates, which makes the grown PCDs as candidates for heat spreaders in different technological applications. High refractive in- dex along with translucent nature of the white freestanding PCDs, make them potential candidate for optical windows.

The Barrier’s Heights and Its Inhomogeneities on Diamond Silicon Interfaces

“…Figure 2 b shows the Raman’s map of the FWHM on an area of 100 µm 2 . There is a generally accepted convention that the value of the FWHM greater than 12 cm −1 means a poor quality diamond, and a value lower than 12 cm −1 of a diamond layer is considered good quality [ 16 ]. The Raman spectrum displays also a broad band peaked at 1544 cm −1 corresponding to the non-diamond carbon form with the predominant sp 2 -hybridization.…”

Introductory Chapter: Engineering Applications of Diamond

“…Diamond has the best mechanical properties alongwith high thermal conductivity [81] and very low dielectric loss tangent [82], which make them the only material that can be used as power transmission windows in the gyrotrons used for fusion reactors [25]. Synthetic diamond detector designed for small field dosimetry is used as a dosimeter for synchrotron microbeam and minibeam radiotherapy to ensure highly localised and precise dose delivery [83].…”

Growth of 4″ diameter polycrystalline diamond wafers with high thermal conductivity by 915 MHz microwave plasma chemical vapor deposition

“…Goyal et al [27] deposited thin (300 nm) nanocrystalline diamond (NCD) films on GaN substrates in Ar/ CH 4 /H 2 mixtures and estimated the TC for NCD to be above that of GaN (130 W m −1 K −1 ), but less than 800 W m −1 K −1 in view of the small (100-200 nm) grain size. Mallik et al [28] reported on a free-standing, translucent PCD film with a TC of 660 W m −1 K −1 ; this relatively low value was due to the poor quality and small thickness (≈80 μm) of the material. A much higher TC of 1800-1900 W m −1 K −1 was reported for free-standing MPCVD PCD disks with diameters and thicknesses up to 119 mm and 2.2 mm, respectively, as manufactured by the Element Six Company [6]; however, no details on the growth process were given.…”