Photoinduced Phenomena in GeO₂–GeS₂ Glasses

Abstract

Mn ions were implanted into GaN thin films with six doses ranging from 10 14 to 5 × 10 16 cm −2 and the samples were subsequently annealed isochronically in three steps at 800, 850 and 900 • C. Structural, optical and magnetic properties of the implanted samples were studied after each annealing. X-ray diffraction measurements exhibited new peaks on the lower angle side of the main GaN peak which are attributed to the implantation induced damage as well as the formation of a GaMnN phase. A dose dependent decrease in the optical band gap and an increase in the Urbach tail were observed from optical transmission measurements. The clear magnetic hysteresis loops were recorded by the magnetometer which revealed the room temperature ferromagnetic ordering in all the implanted samples. Unusual behaviour in the magnetic measurements was observed when saturation magnetic moment decreased in all the samples with an increase in annealing temperature from 850 to 900 • C. This is explained by the out-diffusion of Mn atoms from the samples during high temperature annealing. Annealing temperature of 850 • C for Mn implanted GaN has been suggested as suitable since the samples annealed at this temperature exhibited maximum M s and minimum Urbach energy. Bound magnetic polarons are suggested to be the origin of room temperature ferromagnetic exchange in the samples. XPS measurements indicated that the Mn ions have been incorporated into the wurtzite structure of the host lattice by substituting the Ga sites.

Ag‐photodoping in nano‐structured GeO2‐GeS2 glasses

“…4c. As discussed in Section 4.1, the percolated network of GeS 2 seems to be indispensable to these phenomena [2,3]. Optical gap E g (squares) [3], PL peak position (upper triangles) [12], PL half width (lower triangles) [13], and PL intensity (circles and right-hand vertical axis) [13], which is normalized to unity for GeS 2 .…”

“…4a, an etching rate [14] in Fig. 4c, and two photo-induced effects [2] (photodarkening and volume expansion) in Fig. 4c.…”

“…The data for the volume expansion are plotted after expanding by 10 times. (d) SAXS characteristics with the peak width at 100 cps (red squares) [14] and the X-ray intensity at 2θ = 0.65º (black circles) [14]. (e) Ge electron-spin densities in the dark (black circles) and after bandgap illumination (red squares) [13].…”

“…For GeS 2 , the total spin densities are also shown by triangles. Convex composition variations appear in characteristics of small angle X-ray scattering [14] (SAXS) in Fig. 4d and electron spin resonance [13] (ESR) in Fig.…”

“…For such purposes, an oxy-chalcogenide glass is one of much interest, since the glass contains characteristically different ionic and covalent bonds. The bonds may produce homogeneous mixed structures [1] or heterogeneous phase-separated structures [2,3], which remains controversial. If the structure is heterogeneous, the two kinds of bonds may build into nano-scale clusters having wide (> 5 eV) and medium (2-3 eV) band-gaps.…”