Afterglow, thermoluminescence and optically stimulated luminescence characterization of micro-, nano- and ultrananocrystalline diamond films grown on silicon by HFCVD

The exceptional combined properties of diamond such as, high hardness, corrosion resistant, high thermal conductivity, chemical inertness, non-toxicity and biocompatibility makes it a good candidate for applications in a new generation of optoelectronics, electronics, and biomedical devices. This paper focuses on describing systematic studies on the synthesis of polycrystalline diamond films and characterization of their optoelectronic properties. The studies focused on characterizing the relations among the structure, surface morphology and grain size of the polycrystalline diamond films investigated and the afterglow (AG) and thermoluminescence (TL) and optically stimulated luminescence (OSL) of the diamond films. Three different types of polycrystalline diamond films were investigated, namely: microcrystalline diamond (MCD, ≥1 μm grain size), nanocrystalline diamond (NCD, ≥10–100s nm grain size) and ultrananocrystalline diamond (UNCD, 2–10 nm grain size) grown on Si (111) substrate by hot filament chemical vapor deposition (HFCVD). The MCD films were grown for 8 h. and the NCD films were grown for 4 h. on substrates surfaces heated to ~800 °C, using a mixture of CH₄ (3 sccm flow) and H₂ (200 sccm flow) gases flown into an evacuated chamber to a total pressure of 10 Torr. UNCD films were grow for 2 h. on substrate surfaces at ~600 °C, using a mixture of CH₄ (1 sccm flow), H₂ (5 sccm flow), and Ar (45 sccm flow) gases flown into an evacuated chamber to a total pressure of 10 Torr and. The MCD and NCD films showed the typical Raman spectra (using visible 532 nm laser wavelength) for diamond with a well-defined peak at 1332 cm⁻¹ indicating good quality of the diamond structure. The Raman of the UNCD film showed the characteristic D (~1344 cm⁻¹) and G (~1389 cm⁻¹) bands noticeable in visible Raman (532 nm laser wavelength). After beta irradiation, all films exhibited pronounced AG, TL and OSL signals with similar glow and decay curves, with intensities depending on diamond film structure.