Optical properties and functional groups characterization of commercial HPHT micro-diamond samples

In the present work, we provide a detailed characterization of commercial high-pressure, high-temperature microdiamond (HPHT-MD) powders composed of particles of different micron range sizes, with the purpose to assess the diamond crystal quality, defects, and surface composition of commercially available microdiamond specimens. The properties and potential applications of HPHT-MD depend on the morphological and structural characteristics, impurities content, surface chemistry, HPHT process, cleaning, and purification methods used. Commonly this important information is unknown and not provided by the suppliers. Four commercial HPHT-MD powders samples with 10–600 μm range size, acquired from PlasmaChem GmbH, were characterized by Raman, Photoluminescence (PL), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Energy-dispersive Spectroscopy (EDS), and X-ray Photoelectron Spectroscopy (XPS). The findings indicated that the samples were composed of various polyhedral crystals of different sizes that exhibited a characteristic XRD spectrum of cubic structure with peaks at 43.8° and 75.5° attributed to the (111) and (220) planes, respectively. Raman spectra exhibit a peak around 1327 cm⁻¹ and 1334 cm⁻¹ related to the sp³ carbon bond, and a broad band around 1440 cm⁻¹ assigned to the presence of trans-polyacetylene. FTIR spectroscopy and XPS studies allowed the identification of the diamond C–C bond, sp³ hybridized carbon, C–H bonds, C–O, OH, and C[dbnd]O functional groups. Despite the complex elemental composition, it was found that the FTIR spectra for randomly selected specimens were similar. Furthermore, EDS indicated that the crystals are composed of C (76.2–94.5 wt%) and O, Al, Fe, Br, Ca, Si, Mg, and N in smaller concentrations. Our results demonstrate that the HPHT-MD samples possess optical, structural, and surface properties comparable to those of high-quality synthetic diamond, making them suitable for biosensor applications and radiation detection and dosimetry.