ИСТИНА

There is a wide range of fields interested in luminescent diamonds: quantum information technologies; optical biomarkers, and scintillators (X-ray beam monitors). Intense hard x-ray pulses at high repetition rates of >100 Hz at new generation light sources such as x-ray free-electron lasers or insertion devices at 4t􀀀 generation storage rings formulate new requirements to the scintillators to be used to monitor their radiation: fluorescence decay time faster than 100 ns; low Z, exceptional radiation hardness and high thermal conductivity to withstand intense hard x-ray pulses at high repetition rate. Diamond materials offer a variety of fast fluorescence types, which potentially can be of interest for such applications. Here we present recent results of cathodoluminescence study performed with a pulsed source on self-supporting diamond films of new morphology composed of diamond micropy-ramids produced by the combination of chemical vapor deposition technique and selective oxidation. The spectrum of cathodoluminescence was dominated by a fast wide band peaking at 430 nm. This luminescence had a nonexponential decay, which could be fitted by three components with τ 0.4, 4 and 15 ns. In the literature this band is known as A-band and for the first time was observed some 30 years ago. However we didn’t find any data on charac-teristic decay time of this luminescence, thus it was determined for the first time. The origin of A-band was initially explained by donor-acceptor recombination, later on it was attributed to dislocations and other imperfections of the crystal. It was opposed to excitonic emission: in high-quality crystals excitonic emission was observed while in those with dislocations A-band was dominating and excitonic emission was absent. This was different in our case: we did observe both excitonic emission (narrow band peaking at 236 nm) and the “A-band” at 430 nm. This could be due to the non-uniform distribution of luminescence centers along the pyramids - this is the assumption to be verified during further studies. Well-known narrow luminescence lines attributed to N-V centers (576 nm, FWHM 3 nm) and Si-V centers (738 nm, FWHM 4 nm) were observed as well and their characteristic decay times determined: it was 3 ns for the N-V luminescence and 4 ns for Si-V luminescence.