Muonium studies of p-type semi-conducting diamond under conditions of UV-visible illumination

This work reports on the promptly forming fraction and the spin relaxation rate of the isotropic muonium (Mu(T)) component in p-type semi-conducting d iamond, measured under the condition of illumination. The data are the firs t such investigations for diamond. A broad band illumination with wavelengt hs ranging from 0.5 mu m to 3 mu m was obtained from a Xenon lamp. The ener gy of the photons was sufficient to excite electrons from the valence band to the 0.28 ppm boron impurity band (0.37 eV). The Transverse Field Muon Sp in Rotation (TF-mu SR) measurements were conducted as a function of tempera ture, ranging from 5 K to 300 K. An illumination effect at temperatures bel ow 100 K is observed. It is not yet clear from these data whether the effec t is due to MuT scattering off delocalized holes, which are removed by illu mination or whether there is prompt trapping of MuT at boron impurities (pa ssivation) which is affected by illumination.