Due to their exceptional properties cubic boron nitride (cBN) is considered as real advanced and multifunctional material for applications in microelectronics, optoelectronics, cold emission devices, detectors and of high power microwave devices all working in hard conditions.
Luminescence as spectroscopy techniques of characterization of cBN has been used by us for many years. EPR analysis of cBN was rarely used. It is clear now in which way these methods can deliver knowledge about defective structure of cBN and which difficulties can be obtained. As compared to diamond and GaN cubic boron nitride has shown itself as very difficult to be explored in luminescence as well as in EPR analysis. The main reason of these problems is that the material is very pure to show luminescence and EPR output as result of doping or other external influence.
As diamond has showed a lot of luminescence centers after doping, irradiation and implantation which are most of “inter- center” nature, as GaN has gun a lot of donor-acceptor pairs and excitons optically active defects…CBN, probably, behaves in different way.
After irradiation and implantation with different ions cBN has shown just 5 optically-active defect, RC-1, RC-2, RC-3 and RC-4 considered as simple Frenkel pairs composed of nitrogen vacancy and some unknown defects. The last fifth optically-active defect C was registered after ion implantation and was considered as large complex based on nitrogen vacancies. Just beryllium has performed itself in luminescence spectra as very reliably identified. A nature of electronic transitions, which is a reason of luminescence centers in cBN, is sorted between the “inter –centers” ones and donor-acceptor recombination. Just one luminescence center related to exciton in cBN was considered.
The same picture in there in EPR analysis. Still 3-4 paramagnetic active defects are obtained in cBN. No irradiation, implantation or doping of cBN has delivered any signals in EPR spectra of cBN. |