X-RAY PHOTOELECTRON SPECTROSCOPY AND OPTICAL STUDIES OF BI-12(GAXBI1-X)O-20-DELTA AND BI-12(ZNXBI1-X)O-20-DELTA SINGLE CRYSTALS

摘要

Bi-12(M(x)Bi(1-x))O-20-delta transparent crystals, where M = Ga (x = 0.63-0.72) or M = Zn (x = 0.57), have been grown by Czochralski technique. A change in the bonding conditions of a minor fraction of bismuth in the sample surface has been confirmed by X-ray photoelectron spectroscopy. This has been attributed to the surface enhanced presence of bismuth in tetrahedral lattice positions (Bi-M) It is suggested that defect centers related with Bi-M cations are responsible for a pre-edge absorption observed for M = Ga. Excitation in this band produce a photoluminescence emission peaking at 608 nm, observed at 15 K. Infrared absorption bands at 636 cm(-1) for M = Ga and 635 cm(-1) for M = Zn were detected and attributed to Bi-M-O vibrations. [References: 26]