Photoinduced effect in Ga–Ge–S based thin films

• Published in: Applied surface science Vol. 252; no. 24; pp. 8738 - 8744
• Main Authors: Messaddeq, S.H., Li, M. Siu, Inoue, S., Ribeiro, S.J.L., Messaddeq, Y.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-10-2006; Elsevier Science
• Subjects: Chalcogenide; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Diffraction gratings; Exact sciences and technology; Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity); Optical constants: refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Photobleacing; Photoexpansion; Physical radiation effects, radiation damage; Physics; Refraction index; Structure and morphology; thickness; Structure of solids and liquids; crystallography; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Thin films; Ultraviolet, visible, and infrared radiation effects (including laser radiation); Thin films; Chalcogenide; Diffraction gratings; Photobleacing; Photoexpansion; Refraction index; Atomic force microscopy; Refractive index; Optical fiber networks; Surface structure; Chalcogenides; Energy gap; Illumination; Mirrors; Absorption edge; Photobleaching; Scanning electron microscopy; Physical radiation effects; X-ray spectra; Dispersive spectrometry; Spectral line shift; Holographic gratings; Thickness; Blue shift; Electron beam evaporation
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2005.12.074

Glassy films of Ga
10Ge
25S
65 with 4
μm thickness were deposited on quartz substrates by electron beam evaporation. Photoexpansion (PE) (photoinduced increase in volume) and photobleaching (PB) (blue shift of the bandgap) effects have been examined. The exposed areas have been analyzed using perfilometer and an expansion of 1.7
μm (Δ
V/
V
≈
30%) is observed for composition Ga
10Ge
25S
65 exposed during 180
min and 3
mW/cm
2 power density. The optical absorption edge measured for the film Ge
25Ga
10S
65 above and below the bandgap show that the blue shift of the gap by below bandgap photon illumination is considerable higher (Δ
E
g
=
440
meV) than Δ
E
g induced by above bandgap illumination (Δ
E
g
=
190
meV). The distribution of the refraction index profile showed a negative change of the refraction index in the irradiated samples (Δ
n
=
−0.6). The morphology was examined using a scanning electron microscopy (SEM). The chemical compositions measured using an energy dispersive analyzer (EDX) indicate an increase of the oxygen atoms into the irradiated area. Using a Lloyd's mirror setup for continuous wave holography it was possible to record holographic gratings using the photoinduced effects that occur in them. Diffraction efficiency up to 25% was achieved for the recorded gratings and atomic force microscopy images are presented.