TEMPERATURE AND INCIDENT BEAM-CURRENT DEPENDENCE OF DOMINANT FREE-EXCITON RECOMBINATION RADIATION FROM HIGH-PURITY CHEMICAL-VAPOR-DEPOSITION (CVD) DIAMONDS

Dominant free-exciton (FE) recombination radiation has been obtained f rom high-purity Chemical vapor deposition (CVD) diamond synthesized on Cu substrates by means of microwave plasma CVD using CH4+O2 diluted w ith H-2. The intensity of FE emission is almost constant between 80 K and 170 K, and is reduced by two orders of magnitude at room temperatu re. The emission increases in proportion to the incident beam current from 1 x 10(-9) A to 2 x 10(-6) A. The spectrum shapes between 200 nm and 600 nm do not depend on the beam current. In addition, the isotopi c effect on the FE emission peak shift has been observed in the spectr um from C-13-enriched (96.6%) CVD diamond for the first time.