Search

Abstract: CVD diamond shows interesting perspectives for the production of high-performance radiation detectors and electronic devices. However, due to a polycrystalline structure, the performance of CVD diamond-based devices may be hampered by the low signal-to-noise ratio associated with high level of conductivity. We consider that the level of conductivity correlates with the presence of graphitic impurities within the polycrystalline samples. Assuming that this graphitic phase is concentrated in the free volume of the interfacial crystal grain-boundaries, we show that the graphitic contamination and bulk leakage conductivity can be reduced by increasing the nucleation density. This effect is mainly due to a better filling of the interfacial space by smaller grains induced during the first stage of CVD deposition process. The 60 μm-thick films were structurally characterized, using Raman spectroscopy and X-ray diffraction (XRD), and electrically by the analysis of room temperature (RT) conductivity and charge collection efficiency, extracted from low-energy X-ray irradiation (8.05 keV). [Copyright &y& Elsevier]

A detailed characterization under 90 Sr β-particles and 4.5 MeV protons micro-beam of a single-crystal CVD diamond-based three-dimensional detector with surface and buried graphite electrodes is presented. Pillar contacts, 300 μm long and 30 μm diameter, were fabricated by using a femtosecond laser operating at 1030 nm wavelength and 400 fs pulse duration. Charge collected under 90 Sr β-particles was measured in front and back irradiation conditions, pointing out that the pillars contribute to the charge collection. Charge collection efficiency (CCE) was measured to be up to 94% under proton beam irradiation. Results of a comprehensive study, including crossed-polarizers imaging, numerical simulation of the electric field distribution, and proton mapping, show that CCE is not affected from the stress induced by the pillar fabrication, and that the electric field strength is high enough to partially compensate for carrier recombination in the defected regions surrounding the pillars. [ABSTRACT FROM AUTHOR]

The DC electronic response of a small area polycrystalline diamond film irradiated by a low energy X-ray beam has been analysed. The relationship between the induced photocurrent and the X-ray flux has been investigated making use of an X-ray absorber method. Aluminium foils have been used to attenuate the direct beam and the metal–diamond–metal device response tested at several electric field values. The X-ray photocurrent shows a linear response of the device that has been observed for a large range of X-ray flux values. [Copyright &y& Elsevier]

In this paper new version of the 6 Li-based neutron spectrometer for high flux environments is described. The new spectrometer was built with commercial single crystal Chemical Vapour Deposition diamonds of electronic grade. These crystals feature better charge collection as well as higher radiation hardness. New metal contacts approaching ohmic conditions were deposited on the diamonds suppressing build-up of space charge observed in the previous prototypes. New passive preamplification of the signal at detector side was implemented to improve its resolution. This preamplification is based on the RF transformer not sensitive to high neutron flux. The compact mechanical design allowed to reduce detector size to a tube of 1 cm diameter and 13 cm long. The spectrometer was tested in the thermal column of TRIGA reactor and at the DD neutron generator. The test results indicate an energy resolution of 300 keV (FWHM), reduced to 72 keV (RMS) excluding energy loss, and coincidence timing resolution of 160 ps (FWHM). The measured data are in agreement with Geant4 simulations except for larger energy loss tail presumably related to imperfections of metal contacts and glue expansion. [ABSTRACT FROM AUTHOR]

The proton micro-beam of the CNA accelerator in Seville has been used to test two detectors based on single crystal diamond grown by chemical vapor deposition. The first diamond has a more traditional design, with dimensions 4.5 × 4.5 × 0.5 mm 3 , and features a large contact of the same size as the crystal. The second, with dimensions 2.0 × 2.0 × 0.3 mm 3 , features a small contact of 0.5 × 0.5 mm 2 . By using the micro-beam, the map of the charge collection efficiency for both the detectors have been measured. We show that the charge collection efficiency of the diamond with large contacts is generally uniform, while the diamond with smaller contacts needs further developments in this respect. A proof of principle test with a fast electronic chain has been performed to demonstrate that spatially resolved pulse shape analysis can be performed with this system. The micro-beam allowed also studying radiation-induced permanent damage and polarization, which are two irradiation effects of importance for the development of diamonds used in spectroscopy applications. [ABSTRACT FROM AUTHOR]

Nanocrystalline diamond (NCD) films with and without a diamond buffer layer (BL) have been grown on p-type silicon substrates by microwave plasma enhanced chemical vapor deposition technique at different values of deposition temperature (652–884 °C). The photo- and thermionic electron emission properties of NCD films have been investigated, illustrated and explained by analyzing the surface morphology and the grain shape determined by atomic force microscopy, the chemical-structural properties by Raman spectroscopy and nanocrystallites size by X-ray diffraction. The NCD films with BL grown at the highest deposition temperature have shown the highest photo- and thermionic emission currents. [ABSTRACT FROM AUTHOR]