Luminescence study of thermal treated and laser irradiated Bi12GeO20 and Bi12SiO20 crystals

Abstract

Changes on the defect structure of Bi12GeO20 (BGO) and Bi12SiO20 (BSO) crystals induced by thermal treatments and laser irradiation have been studied by means of cathodoluminescence in the scanning electron microscope. The results have been compared to those previously reported for untreated and electron irradiated samples and recombination mechanisms responsible for some of the observed luminescence bands are discussed. Annealing of BGO samples causes the appearance of a new luminescence band at about 390 nm. The centers responsible for this band decorate the deformation slip bands in quenched BGO as observed in the cathodoluminescence images. The emission observed in BSO in the same spectral range is quenched during the annealing treatment. The annealing induced reduction of Bi ions to metallic Bi appears to be related to the quenching of a band at 640 nm observed in untreated samples.

Study on photoluminescence of thermally treated Bi12GeO20 and Mo:Bi12GeO20 crystals

“…Up to the present, there are some works [9][10][11][12][13][14] about the optical properties of Bi 12 GeO 20 . Cremades [11] studied the luminescence emission of Bi 12 GeO 20 under low temperature (below 200 K) and discovered an emission band centered at about 640 nm.…”

“…Cremades [11] studied the luminescence emission of Bi 12 GeO 20 under low temperature (below 200 K) and discovered an emission band centered at about 640 nm. He also investigated cathodoluminescence of thermal treated and laser irradiated Bi 12 GeO 20 and detected that annealing of Bi 12 GeO 20 caused the appearance of an emission band at 390 nm [12]. The intrinsic luminescence of Bi 12 GeO 20 has recently been clarified by Itoh's group [15,16], They found that the 450 nm luminescence of Bi 12 GeO 20 rapidly decreases in intensity with increasing T and disappears above 50 K. The PL of Bi 12 GeO 20 at room temperature has not been reported in the previous works.…”

“…Bismuth germanate (Bi 4 Ge 3 O 12 ) and bismuth germanium oxide (Bi 12 GeO 20 ) are usually abbreviated as BGO in common. The Bi 4 Ge 3 O 12 crystal is the well-known material widely used as a scintillator [1, 2], the structure of Bi 4 Ge 3 O 12 consists of a regular arrangement of GeO 4 tetrahedron and distorted BiO 6 octahedron sharing oxygen atoms of the GeO 4 [3].…”

“…The Bi 12 GeO 20 crystal structure is described by the cubic space group I23. The unit cell of Bi 12 GeO 20 contains two formula units, the Ge atoms residing in the center and in the vertices of the cube. Each one of the Ge atoms is tetrahedrally coordinated by oxygen atoms.…”

“…The Bi 4 Ge 3 O 12 crystal is the well-known material widely used as a scintillator [1, 2], the structure of Bi 4 Ge 3 O 12 consists of a regular arrangement of GeO 4 tetrahedron and distorted BiO 6 octahedron sharing oxygen atoms of the GeO 4 [3]. The Bi 12 GeO 20 crystal structure is described by the cubic space group I23.…”