Excellent optical properties of chalcogenide glasses make them interesting for optoelectronic devices in the visible (VIS) and, especially, in the near- and mid-infrared (NIR and MIR) spectral regions. The rare-earth (RE3+) doped Ga17Ge25As8.3S65 glasses were prepared in evacuated (~10−5 Pa) silica-glass ampoules which were heated up to 1000 °C at 2–4°C min-1, and then the melt was quenched. The absorption and photoluminescence spectra in the visible and near IR regions for GA1.7Ge25As8.3S65 doped with rare-earth RE+) ions (Sm3+, Nd3+, Pr3+, Dy3+ and co-doped with Ho3++Dy3+) are investigated. The energy transfer of the absorbed light in the broad band Urbach region of the host glass to the RE3+ ions is suggested for increasing the emission efficiency. The investigated Ga17Ge25As8.3S65 glasses doped with RE3+ ions are promising materials for optical amplifiers operating at 1300 and 1500 nm telecommunication windows.
Chalcogenide glasses are attractive materials due to its application in photonics and optoelectronics. Chalcogenide glasses GexAsxSe1-2x (average coordination number Z=2.15÷2.90) and (As4S3Se3)1-xSnx (average coordination number Z=2.4÷2.56), which contain elements of IV group of the Periodic Table, such as Ge and Sn are important for a wide range of technical applications, such as infrared optical elements, acousto-optic and alloptical switching devices, holographic recording media, diffractive optics, photonic crystals, etc. [1, 2]. Raman spectroscopy is an efficient method for obtaining information on the local structure of the disordered material, especially when the composition is varied. In this paper are reported the Micro-Raman spectra of GexAsxSe1-2x and (As4S3Se3)1-xSnx bulk glasses and amorphous thin films. The Micro-Raman spectra of bulk glasses and thermally deposited amorphous (As4S3Se3)1-xSnx thin films consist of two broad bands located at around ν=236 cm-1 and ν=345 cm-1, which corresponds to the symmetric stretching vibration modes of AsSe3/2 and AsS3/2 pyramids, respectively. Tin impurities didn’t change the shape of Micro-Raman spectra, but shift the both bands to low frequency region. The Micro-Raman spectra of bulk glasses and thermally deposited amorphous (GexAsxSe1-2x thin films consist of one main vibration band located at around ν=246 cm-1 for lower concentration of Ge and As, and is attributed to (AsSe1/2)3 pyramidal units. With increasing of Ge and As concentrations this band shifts to lower frequency region up to ν=236 cm-1 for x=0.30. The vibration band situated around ν=205 cm-1 is attributed to Ge(Se1/2)4 tetrahedral units and increase in the intensity with increasing of Ge and As concentrations. Some shoulders in high frequency regions at ν=365-390 cm-1 and ν=500-530 cm-1, caused by the presence of As-Se bands and Se-Se chains also was observed.
Arsenic selenide glasses are well known as high photosensitive materials with a wide range of application in optoelectronics and information storage systems. Besides, it was found that the impurities influence the electrical and photoelectrical characteristics of the amorphous material, due to the changes in the density of localized states. Introduction of the elements of IV group of periodic table in selenide and sulphide glasses, such as Sn and Ge, conduct to the appearance of tetrahedral structural units in the base glass, which change the coordination number. These particularities lead on non-monotonous dependence of physical properties on the glass composition. Besides that, recently it was established, that in the disordered network of glassy system GexAsxSe1-2x exists three distinct phases, floppy, intermediate and stressed rigid, and the dependence of physical properties of the average coordination number Z. In the present paper the experimental results on steady-state photoconductivity of amorphous GexAsxSe1-2x and (As4S3Se3)1-xSnx thin films are presented and discusses. It was shown, that the spectral distribution of the stationary photoconductivity for both glass systems depends on the composition and polarity on the illuminated electrode. The experimental results are discussed in terms of multiple trapping model for amorphous materials, with exponential distribution of localized states in the band gap.
Chalcogenide glasses are important materials for a wide range of technical applications, such as infrared optical elements, acousto-optic and all-optical switching devices, holographic recording media, diffractive optics, photonic crystals, etc. Optical investigation such as infrared reflectance and Raman spectroscopy are efficient tools for obtaining information on the local structure of the disordered material, especially when the composition is varied. In this paper we present the Raman spectra of bulk and amorphous thin films as-deposited and after light irradiation of (As4S3Se3)1-x:Snx (0 ≤ x ≤ 10 at. % Sn) chalcogenide glasses. The Raman spectra of (As4S3Se3)1-x:Snx glasses consist of two broad bands located at around ν = 236 cm-1 and ν = 345 cm-1, which corresponds to the main vibration modes of vitreous As2Se3 and As2S3. Tin impurities didn’t change the shape of Raman spectra, but shift the both bands to low frequency region. The maximum situated at around ν = 236 cm-1 and ν = 345 cm-1 are characteristic for all investigated glass compositions and are attributed to the symmetric stretching vibration modes of AsSe3/2 and AsS3/2 pyramids, respectively. The light exposure of amorphous (As4S3Se3)1-x:Snx thin films shift the main maximums of Raman spectra toward the lower energies.
Amorphous arsenic trisulfide (As2S3) and arsenic triselenide (As2Se3) are among widely investigated amorphous materials due to its interesting electrical, optical and photoelectrical properties. In order to improve the physical properties and recording characteristics, and to extend the spectral range of photosensibility, a special interest represents the mixed amorphous materials, like (As2S3):(As2Se3). Chalcogenide vitreous semiconductors (ChVS) of the As-S-Se system exhibit photostructural transformations with reversible and irreversible properties, and are promising materials as registration media for holography and optical information, for fabrication of diffractive elements, and other optoelectronic applications. Because many optoelectronic devices on amorphous semiconductors are based on the photoconductivity effect, special interests represent investigation of the stationary and non-stationary characteristics of photoconductivity. In this paper the experimental results of steady-state photoconductivity and holographic characteristics of amorphous (As4S3Se3)1-x:Snx thin films are presented.
It was shown that the photoconductivity spectra depend on the polarity on the top illuminated electrode and on the Sn concentration in the host glass. The photosensitivity of amorphous ((As4S3Se3)1-x:Snx thin films is almost constant for all Sn-containing glasses. The Moss rule was used for determination of the optical forbidden gap Eg from the photoconductivity spectra. It was demonstrated that the investigated amorphous films are sensitive to the light irradiation and can be used as effective registration media for holographic information. The relaxation of photodarkening in amorphous (As4S3Se3)1-x:Snx thin films was investigated and was shown that the relaxation curves of transmittance T/T0 = f(t) can be described the stretch exponential function T(t)/T(0) = A0+Aexp[-(t-t0)/τ] (1-β) . The kinetics of diffraction efficiency growth η(t) was measured by registration of the laser intensity of the 1-st interference maximum versus time exposure. With increasing of Sn concentration in amorphous (As4S3Se3)1-x:Snx thin films up to 6.0 at. % Sn, the diffraction efficiency η increases, than for higher concentrations of tin, decreases.
Thin films of chalcogenide glasses (ChG) of different composition have been used for e-beam recording of diffraction grating structures. The dependencies of diffraction efficiency of gratings on radiation dose were studied. The influence of ChG film composition on diffraction properties of gratings was shown. It was established that the refractive index gratings formed in As2S3 films exhibit high stability during their dark storage. The diffraction efficiency enhancement caused by uniform light irradiation was observed for gratings recorded in As4S3Se3 thin films, doped with Sn. With use of computer-controlled positioning of electron beam both the raster scan and vector patterns were recorded in As2S3 films. In the former case the images from BMP-files were patterned. In the latter case the mosaic of diffraction gratings, producing the multi-beam light diffraction was recorded.
Experimental results on some physical and optical properties of (As2Se3)1-x:Snx and (As4S3Se3)1-x:Snx (x = 0-10 at %) glasses and amorphous films (d~2.0 μm) are presented. The bulk chalcogenide glasses are studied by X-ray diffraction spectroscopy and nanoindentation methods. It is established that the addition of these amounts of tin (x = 0-10 at %) does not lead to significant changes in the physical properties of the glass, such as values of stress and Young’s modulus related to the modification of the density and compactness. It has been found that the addition of these amounts of tin in (As4S3Se3)1-x:Snx does not lead to significant changes in the glass physical properties, such as values of stress and Young’s modulus related to the modification of the density and compactness. The study of the photoplastic effect is performed in situ, with illumination of the bulk and thin film samples during indentation as well as their indentation after illumination with a green laser (λ = 532 nm) at a power of P = 50 mV/cm2. The hardness is calculated from load-displacement curves by the Oliver-Pharr method. A sharp increase in hardness is registered if the tin concentration exceeds a value of 34% Sn. The hardness H of (As2Se3)1-x:Snx films varies between 115 and 130 kg/mm2. It is found that the hardness H of amorphous thin films is generally higher than the hardness of bulk samples with the same chemical composition. In this study, we are focused on the mechanical characteristics of high-purity As2Se3: Snx thin films. Keyword: Chalcogenide glasses, hardness,
Transparent thin films of polyepoxypropylcarbazole polymer were produced using spin-coating technique. Optical
materials constants such as refractive index of thin films and thickness were determined by optical spectroscopy. It was
shown the possibility of variation of film thickness by polymer concentration in solution. It was shown that film
thickness dependence on the concentration of solution is linear. Therefore this linear dependence can be used to predict the film thickness of spin-coated polymers if the solvent is known. The thickness can be varied from 170 nm up to 940 nm for the solution with concentration from 2.5% up to 12.5%. To confirm the validity of our method, we also carried out the interferometric thickness measurements and analysis with a thin film of polyepoxypropylcarbazole. The
difference of obtained results of two methods averaged not more than 5%.
The measured film thickness by transmission spectra of the polymer film was found to be well correlated to the
results of interferometric thickness measurement. The refractive index of the polyepoxypropylcarbazole was 1.62,
which was well above the refractive index of 1.49 for polymethylmethacrylate. It was found that the inclusion of even a
small amount of a photosensitizer, such as CHI3, was effective in producing of high refractive index material with
refractive index 1.64.
The modifications of optical parameters (optical band gap Eg, absorption coefficient α, refractive index n) under light
irradiation by He-Ne laser of the amorphous thin films with different amount of Sn were measured and calculated. In the
present work the transmission spectra of bulk and thin films of [(As2S3)0.5:(As2Se3)0.5]1-x:Snx (x=0; 1; 2 at.%) in the
visible and middle infrared (IR) regions were studied. The red shift of the fundamental absorption edge under light
exposure was observed, and the values of the optical band gap Egopt from the graphics in Tauc coordinates (α hν)1/2=A(hν -
Eg) were obtained. The dispersion of the refractive index was examined. The relaxation of the relative optical
transmission T/T0=f(t) under the light exposure (λ=633nm and λ=543nm) for amorphous [(As2S3)0.5:(As2Se3)0.5]1-x:Snx thin films also was investigated. The relaxation curves of photodarkening under light irradiation were processing using
the stretched exponential presentation of the data: T(t)/T(0) = A0+Aexp[-(t-t0)/τ] (1-β), where t is the exposure time, τ is the
apparent time constant, A characterizes the exponent amplitude, t0 and A0 are the initial coordinates, and β is the
dispersion parameter (0<β<1).
The transmission spectra of bulk and thin films of (As2S1.5Se1.5)1-x:Snx in the visible and near infrared (IR) regions were investigated. Doping of As2S1.5Se1.5 chalcogenide glass with tin impurities essentially reduce the absorption bands of SH (Se-H) and H2O located at ν = 5190 cm-1 and ν = 3617 cm-1, respectively. The amorphous As2Se3:Snx and (As2S1.5Se1.5)1-x:Snx thin films exhibit photoinduced effects under the light irradiation with photon energy above the optical band gap (hν≥Eg), that make its perspective materials for registration of optical and holographic information. The modification of optical parameters (optical band gap Eg, absorption coefficient α, refractive index n) under light irradiation and heat treatment of the amorphous thin films with different amount of Sn was studied. The shift of the absorption edge after light exposure to lower energy region was observed, i.e. the effect of photodarkening take place. The dispersions curves n=f(λ) show a modification of the refractive index n under light exposure. For the glass composition (As2S1.5Se1.5)0.96:Sn0.04 the change of the optical band gap Egopt under light exposure was determined from 1.92±0.02 eV to 1.86±0.02 eV. The similar calculations of the optical constants were done for the amorphous films of glass compositions x=0.03 and x=0.05. The relaxation of photodarkening in amorphous As2Se3:Snx and (As2S1.5Se1.5)1-x:Snx thin films, which is described by the stretch exponential function T(t)/T(0) = A0+Aexp[-(t-t0)/τ](1-α)also wasinvestigated. The experimental results are interpreted in framework of the model of molecular structure of chalcogenide glasses doped with tin impurities.