STRUCTURE AND OPTICAL-PROPERTIES OF SE ACCOMMODATED IN CHANNELS OF ALPO4-5 SINGLE-CRYSTAL

Optical properties are studied for Se species accommodated in channels of an AlPO4-5 single crystal. Polarized Raman spectra show that the S e species is of helical chain structure with D-3 symmetry. The optical phonon modes of the Se chains are shifted towards higher frequencies from that of the trigonal Se crystal, because of the loss of inter-cha in interactions in Se/AlPO4-5. High anisotropic absorption spectra hav e been observed for the Se chains. The lowest excitation energies are shifted towards high energy about 0.6 eV from the band edge transition s of the trigonal Se crystal. The blue shift is attributed to the quan tum confinement of carriers in a Se chain with diameter 7.3 Angstrom. (C) 1998 Academic Press Limited.