CPPP 16P Structure and optical properties of As-Ge-Se layers
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TOLMACHOV, I., PRIBYLOVA, H., LISHINSKY, I., STRONSKI, Alexander, VLCEK, Miroslav. CPPP 16P Structure and optical properties of As-Ge-Se layers. In: Materials Science and Condensed Matter Physics, 13-17 septembrie 2010, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2010, Editia 5, p. 143.
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Materials Science and Condensed Matter Physics
Editia 5, 2010
Conferința "Materials Science and Condensed Matter Physics"
Chișinău, Moldova, 13-17 septembrie 2010

CPPP 16P Structure and optical properties of As-Ge-Se layers


Pag. 143-143

Tolmachov I.1, Pribylova H.2, Lishinsky I.3, Stronski Alexander1, Vlcek Miroslav2
 
1 V.E. Lashkaryov Institute of Semiconductor Physics of the National Academy of Science of Ukraine,
2 University of Pardubice,
3 Vasilii Stefanyk Precarpathian National University, Ivano-Frankivsk
 
Disponibil în IBN: 16 aprilie 2021


Rezumat

Chalcogenide glassy semiconductors (ChGS) are attracting attention of many researches since the discovery of their semiconductor properties in the 1950s. This is due to their unique properties such as transparency in infrared region of spectrum, high stability and a number of photoinduced phenomena (photodarkening, photobleaching, photocrystallysation, etc.). Recently, high attention has been paid to the nonlinear optical properties of ChGS. Measurements of nonlinear refractive index have shown that it’s value can range from 100 to 1000 times of that in silica glass. High nonlinear refractive index combined with moderate to low nonlinear absorption can be exploited in all optical signal processing devices to enhance the performance of telecommunication systems. ChGS are very suitable for these kinds of applications because they are compatible with well established silica-on-silicon and fiber drawing technologies. The nature of glassy state provides an opportunity to adjust the composition and therefore, to tune smoothly the properties of material. Photoinduced phenomena allow the local modification of the material properties by the exposure of light which can be utilized in writing waveguide channels, diffraction gratings, etc. In the present work we have examined chalcogenide films of two compositions: As10Ge22.5Se67.5 and As12Ge33Se55 obtained by thermal vacuum evaporation onto the glass substrate at room temperature. Initial bulk glasses were prepared by direct synthesis in evacuated quartz ampoules. After synthesis ampoules were quenched in cold water. Glass structure was investigated by examining Raman scattering spectra. Raman spectra were taken using IR Fourier spectrophotometer Bruker IFS55 Equinox with FRA-106 attachment. Nd-YAG laser light at wavelength 1.06 mm was used for excitation. The main band in the spectra of both glasses is located near 200 cm-1. It is a characteristic of As-Ge-Se system. The band near 200 cm-1 and the mode at 215 cm-1 correspond to the vibrations in corner-shared and edge-shared Ge(Se1/2)4 tetrahedra, respectively, in both glasses. However, in the case of As12Ge33Se55 glass, this band have more complicated shape. The most distinguishable difference is the feature near 178 cm-1. We ascribe this feature to the presence of Ge-Ge bonds which are located in the Ge2(Se1/2)6 ethane-like nanophase. This phase appears to be demixed from the network of the glass and form separate nanophase inclusions in the overall glass backbone. Thermal properties of the glasses were investigated using differential scanning calorimeter NETZSCH DSC 404. Values of Tg obtained from DSC measurements are equal to 381 °C for As12Ge33Se55 glass and 290 °C for As10Ge22.5Se67.5 glass. Optical constants and thicknesses of the films were obtained from transmission spectra using the method proposed by Swanepoel [1]. Optical transmission spectra of the films were obtained in the 0.4 – 2.5 μm range. Optical band gap, Eg, was determined from the Tauc law. Nonlinear refractive indexes at standard telecom wavelength (λ = 1500 nm) were estimated from the relation proposed recently by Sanghera et. al. [2]. Estimation gave n2 = 3.7·10-17 m2/W for As12Ge33Se55 film and n2 = 1.2·10-17 m2/W for As10Ge22.5Se67.5 film. Such high values of third order nonlinearity make these glasses suitable to be considered as perspective materials for all-optical switching and other optical signal processing applications.