As2S3 Films Research Articles

Study of the dynamics and mechanisms of deformation of thin chalcogenide As(Ge)2Se3 films by nanoindentation

The mechanical properties of As2Se3 and Ge2Se3 thin films have been studied by the method of quasi-static nonoindentation. The mechanisms of formation and recovery of the indentations in the studied materials have been analyzed under conditions of their local loading. It has been revealed that the deformation mechanism of the chalcogenide films changes in going from As2Se3 to Ge2Se3. It has been found that, during deformation of the As2Se3 film under the indenter, the accumulation of plastic deformation prevails, and, for the Ge2Se3 film, the substantial mechanism is the relaxation of its deformation.

Photoinduced macroscopic vector deformations in chalcogenide glasses

Photoinduced vector deformations in amorphous Se films on viscous and rigid substrates have been studied for comparison with those in As2S3. In both the films, illumination of focused and unfocused linearly-polarized bandgap light produces, respectively, anisotropic M-shape deformations and wavy wrinkles. The M-deformations occur in parallel to the electric field, but the wavy directions are contrastive; parallel and orthogonal to the electric field in Se and As2S3 films on grease. The unfocused illumination also produces corrugations in As2S3 films on glass substrates. We assume that atomic and optical forces are responsible for these deformations.

Photoinduced phenomena in nano-dimensional glassy As_2S_3 films

Photoinduced anisotropy in nano-dimensional (ND) thin films (<50nm thick) of chalcogenide glasses is observed for the first time. Results of photoinduced dichroism and photodarkening effect in 10, 20, 50 and 100 nm glassy As2S3 films are presented and compared with photoinduced phenomena in thick films (>1µm). ND As2S3 films are shown to function also as efficient photoresists. Preliminary model based on two exponential rate processes involving defects generation and stabilization is proposed explaining the main features of the photoinduced phenomena. These observations widen the range of applications of chalcogenide glassy films such as for higher capacity of optical data storage and for the photoalignment of liquid crystals.

Broadband dielectric response of amorphous arsenic triselenide layers grown by different methods

The polarization processes in arsenic triselenide (As2Se3) films grown by thermal vacuum deposition and high-frequency ion plasma sputter methods have been studied in alternating electric field at frequencies in a range of 10−2 to 107 Hz and temperatures of 253–343 K. It has been established that the method of preparation significantly influences the dielectric response of samples, which is related to specific features of the localized energy states.

Photoinduced Volume Changes of Obliquely and Flatly Deposited Amorphous AsSe Films Universal Description of the Kinetics

Recently, we have constructed structural models for flatly deposited amorphous Se (a-Se) and using these configurations we have developed atomic scale model of photoinduced volume changes in this type of films. In this paper the same work on obliquely deposited thin film is presented. Universal description for the kinetics of photoinduced volume change in chalcogenide glasses is proposed based on our results. Our model containing reversible (transient) and irreversible (metastable) parts for kinetics fits well the experimental results of both obliquely and flatly deposited a-AsSe thin films. Finally, we make a brief comment on stretched exponential function which could also provide a quite good fit to experimental data.

Photoinduced Volume Changes of Obliquely and Flatly Deposited Amorphous AsSe Films Universal Description of the Kinetics

Photoinduced Volume Changes of Obliquely and Flatly Deposited Amorphous AsSe Films Universal Description of the Kinetics

Photoinduced mass transport in soft materials

The surface relief grating formation in amorphous As2S3 and azo-benzene polymer films strongly depends on the polarization state of recording beams. The surface relief grating formation efficiency of s-s and p-p recording beam combination can be essentially enhanced by additional illumination with orthogonal polarization. It is shown that the direction of mass transport on the film surface is determined by the direction of light electric vector.

Photoinduced mass transfer in amorphous As2S3 films

AbstractThe surface relief grating formation in amorphous As2S3 films strongly depends on the polarization state of recording beams. The surface relief grating formation efficiency of s‐s and p‐p recording beam combination can be essentially enhanced by additional illumination with orthogonal polarization. It is shown that the direction of mass transport on the film surface is determined by the direction of light electric vector (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Preparación de películas delgadas de AS2S3 por depósito químico con perspectivas de aplicacíon en celdas solares

In this paper we obtained thin films of As2S3 by chemical bath deposition. The films were prepared at a temperature of 80 ºC for 3 hours each deposit. They were thermally treated at 180 ºC and 250 ºC for 30 minutes for 1 hour, respectively. The energy gap was calculated 2.9 eV. The conductivity was around, 3.62X10-1 (O*cmr'.

Kinetics of laser-induced photodarkening in arsenic based chalcogenide glasses

Photoinduced changes in the optical properties of chalcogenide glass thin films have been studied extensively but usually only permanent changes were recorded through measurements before and after exposure to pump light. To understand the progression of such effects, in this paper we report in situ measurement of transient changes in the optical transmission of amorphous As2Se3, As5Se5 and As4Se3 thin films during their exposure to a He–Ne laser which has photon energy close to the bandgap of the studied compositions. Mathematical expressions are established, which describe accurately both the light intensity and time dependences of photodarkening. The structural origin of the observed changes is discussed briefly.

Whey protein-okra polysaccharide fraction blend edible films: tensile properties, water vapor permeability and oxygen permeability

A hot-buffer-soluble-solid fraction (HBSS) and an alkaline-soluble-solid fraction (ASS) of okra polysaccharides (OKP) were obtained using sequential extraction. These fractions were combined with whey protein isolate (WPI) and glycerol (Gly) plasticizer to form blend edible films. Effects of OKP fraction and content on tensile properties, water vapor permeability (WVP) and oxygen permeability (OP) were determined. HBSS film had significantly higher percent elongation (%E) and lower elastic modulus (EM), WVP and OP than ASS film. Increasing HBSS or ASS content in blend films with WPI significantly reduced film tensile strength and EM and increased film %E and WVP. OP values for WPI-HBSS blend films were significantly lower than OP for WPI or HBSS film. WPI-HBSS and WPI-ASS blend films had lower WVP and OP than WPI films with equivalent tensile properties. WPI-HBSS blend films have higher WVP and lower OP than WPI film or HBSS film, indicating unique interactions between WPI and HBSS. Compared to WPI film, WPI-HBSS blend films have improved flexibility, stretchability and oxygen barrier. Different HBSS and ASS compositions and structures are responsible for property differences between HBSS and ASS films and between WPI-HBSS and WPI-ASS blend films.

Determination of the quantitative composition of As-Se and Ge-Se glasses and films by X-ray fluorescence analysis

A method of standards has been proposed for determining the quantitative contents of germanium, arsenic, and selenium in vitreous samples and films of the As1 − xSex and Ge1 − xSex compositions with the use of X-ray fluorescence analysis. The application of this technique makes it possible to determine the quantitative composition of As1 − xSex and Ge1 − xSex glasses and films with an accuracy of ±0.001 with respect to the parameter x.

Influence of fine-grained vanadium-based layers on the photoresponse multiplicity in structures with amorphous As2Se3 films

The fabrication of vanadium-based fine-grained structures including those with a branched (fractal) surface is described. The application of amorphous As2Se3 films on these fractal surfaces is shown to increase the multiplicity of photoresponse from the structure.

Ab initio calculations and the effect of atomic substitution in the Raman spectra of As(Sb,Bi)2S3 films

AbstractThe comparative analysis of the calculated and experimental Raman spectra of non‐crystalline As2S3, Bi2S3 and Sb2S3 films (i.e. with exchanging As to Sb, Bi) obtained by flash evaporation on glassy and silicon substrates was performed. The spectra were interpreted and analysed using the results of molecular modelling and ab initio calculations. The structural models used for calculations include both basic building blocks and other types of atomic clusters known for As‐S, Bi‐S, and Sb‐S binary systems. The influence of atomic substitution on the nanostructure of flash evaporated As(Sb,Bi)2S3 films were investigated, observed photo‐induced phenomena and related peculiarities were analysed using results of ab initio calculations and discussed in detail. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

On nanoheteromorphous structure in amorphous As2S3 films prepared by different methods

AbstractBy the method of Raman spectroscopy as well as the methods of thermo‐gravimetric and differentially‐thermal analyses the structure of amorphous As2S3 films prepared by thermal evaporation in a vacuum and by radio frequency ion‐plasma sputtering has been studied. The techniques are strongly differing in the conditions of substance vaporization and condensation of atoms on a substrate. It was shown that the concept of nanoheteromorphism can be used to the description of these amorphous films structure. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Dynamics of principal photoinduced effects in amorphous chalcogenides: In‐situ simultaneous measurements of photodarkening, volume changes, and defect creation

AbstractTo understand the direct relation among photodarkening (PD), photoinduced volume change (PVC), and photoinduced defect creation (PDC), we perform in‐situ simultaneous measurements of all three phenomena, i.e. optical absorption coefficient (for PD), surface height (for PVC), and photocurrent which monitors PDC, in amorphous As2Se3 films. The time evolution of PDC during light excitation is empirically described by a stretched exponential function: 1 ‐ exp[‐(t /τ)β], where τ is the effective response time and β (< 1.0) the dispersion parameter, while we have found that the PVC and PD were essentially given by a simple exponential function (β = 1). The value of τ for the PDC is very much smaller than those for the PVC and PD. As the time evolutions for all three phenomena are independent of each others, there may be no direct relationship among them. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Distribution of relaxators in modified films of arsenic triselenide

The relaxation time distribution functions and related characteristics have been calculated from the decay curves of isothermal polarization current for amorphous films of undoped and bismuth-doped As2Se3. It has been revealed that the method for preparing the samples and the amount of the introduced dopant substantially affect the relaxator distribution in the systems under investigation. The factors responsible for the observed effects have been discussed.

On the photodissolution kinetics of silver in glassy As2S3

Abstract The kinetics of the photodissolution of Ag into glassy As2S3 films and its dependence on temperature have been studied by monitoring the changes that occur both in their transmission spectra and transmission of weakly absorbed broadband light. It was shown that besides of a low induction period, the photodissolution kinetics consists of two linear steps with different activation energies, followed by a parabolic tail. The transitions between photodissolution steps was found to be not monotonous and explained in terms of Elliott’s model, which asserts a simultaneous ionic and electronic charge transport controlled by chalcogenide properties, illumination and temperature. The evidence is given that the islanding of Ag layer in the course of photoreaction, results in an inversion of maxima and minima of transmission spectra. It is suggested that the islanding of Ag layer is not a consequence of a non-uniform dissolution but arises itself at critical thickness, at which Ag forms a continuous film.

Dry etching characteristics of amorphous As2S3 film in CHF3 plasma

The authors describe the dry etching characteristics of amorphous As2S3 films in CHF3 plasma and the development of an optimized fabrication process for compact waveguides. The observed etching behavior is due to the relative densities of fluorine atoms, polymer precursors, and ions in the plasma which are controlled by the process parameters. In particular, the flow rate of the CHF3 gas has a significant influence on the etched profile and surface roughness as well as the etch rate of the As2S3. The profile evolves from isotropic to vertical with the flow rate due to passivation by increasing polymer deposition on the sidewalls. Such passivation also helps achieve smooth sidewalls because it inhibits differential etching between the phases in the inherently phase-separated As2S3 film, which otherwise results in a grainy and rough etched surface. At the highest flow rate, however, excessive polymer deposition occurs and this results in positive-sloped sidewall and grassy etched surface due to micromasking.

Annealing-induced reduction in nanoscale heterogeneity of thermally evaporated amorphous As2S3 films

The morphology and structural order of thermally deposited and annealed amorphous As2S3 films have been investigated using high resolution transmission electron microscopy. It was found that both the as-deposited and annealed films contained sparsely distributed nanocrystallites of the orpiment As2S3 crystalline phase. However, from selected area electron diffraction both films appeared amorphous. Fluctuation electron microscopy revealed that the as-deposited film contained greater nanoscale inhomogeneity. Low temperature annealing reduced the nanoscale inhomogeneity and resulted in a more homogeneous and energetically favorable network. The reduction in nanoscale inhomogeneity upon low temperature annealing was accompanied by the appearance of a first sharp diffraction peak in the diffraction pattern. This first-sharp diffraction peak has been attributed to chemical ordering of interstitial voids. Our measurements suggest that this chemical short-range ordering is associated with the dissolution of the energetically unfavorable larger correlated structures that contribute to the inhomogeneity of the as-deposited film.