Mil. Vlcek

The study of photo- and thermally-induced diffusion and dissolution of Ag in As30S70 amorphous films and its reaction products

Kinetics of photo- and thermally-induced diffusion and dissolution (PIDD and TIDD) of silver in a-As30S70 films were measured by monitoring the change in thickness of the undoped chalcogenide using a modified computer-controlled reflectivity technique. Silver-concentration profiles during photo- and thermally-induced solid-state reactions were traced by means of Rutherford backscattering spectroscopy (RBS). The enthalpy of photo- and thermally-induced reactions was measured by means of differential photocalorimetry and quasi-isothermal temperature-modulated differential scanning calorimetry (DSC), which are shown to be connected with the chemical reaction: Ag+As3S7=AgAsS2+As2S5.

Kinetics of optically- and thermally-induced diffusion and dissolution of silver in spin-coated As33S67 amorphous films; their properties and structure

The As33S67 amorphous films were prepared by standard spin-coating technique. Prepared films were stabilized in a vacuum and then annealed in inert argon atmosphere. Silver film was deposited on top of As33S67 film by vacuum thermal evaporation technique. The kinetics of optically- and thermally-induced diffusion and dissolution of silver in As33S67 amorphous films prepared by spin-coating technique were measured by optically monitoring the change in thickness of undoped chalcogenide during broadband illumination. Compositions of reaction products and silver diffusion profiles in different stages of the photostimulated process have been determined by Rutherford backscattering spectroscopy. Optical and Raman spectroscopies were used to establish the optical properties and structure of the films.

Spin-coated Agx(As0.33S0.67)100−x films: preparation and structure

Abstract We report for the first time on the preparation of samples of Ag x (As 0.33 S 0.67 ) 100− x (from x =0 to 25 at.%) amorphous films by a standard spin-coating technique from n -butylamine solution of the glass constituents. Prepared films were stabilized by annealing in a vacuum furnace purged by inert argon atmosphere. The chemical composition of the spin-coated films has been established. Measurements of the chemical and physical properties of prepared films have been carried out using techniques such as UV/VIS/NIR spectroscopy to characterize the optical properties of films, FTIR and Raman spectroscopy to control the embedded organic solvent content in films and to determine the films structure.

Thermomechanical and thermoelectrical properties of vanadyl phosphate dihydrate

Thermoelectric power and XRD of layered VOPO[sub 4][center dot]2H[sub 2]O have been studied for dependence on temperature. The results of thermomechanical analysis (i.e. thermal changes of the thickness of the crystal across the layers) correspond to the changes of basal spacing during heating. The values of the dehydration temperatures have been determined. The conductivity caused by positive charge carriers is predominant in vanadyl phosphate hydrates, whereas conductivity in anhydrous VOPO[sub 4] is electronic, as it follows from the thermoelectric power measurements.

Ag–Sb–S amorphous chalcogenide thin films prepared by optically induced dissolution and diffusion of silver

Abstract The kinetics of optically induced dissolution and diffusion of silver in Sb33S67 films were measured by monitoring the change in thickness of the undoped chalcogenide using a modified computer-controlled reflectivity technique. Silver concentration was traced by the means of energy dispersion X-ray microanalyzer. The composition of the Sb–S films was chosen to be Sb33S67, which is the most favorable for optically induced solid-state reaction, because it yields homogeneous photodoped products. A new technique of step-by-step optically induced solid state reaction of Ag into Sb33S67 amorphous films, which has allowed the design of films with exact silver concentration and the study of their properties, is reported. The host Sb33S67 films were photodoped by dissolving a thin (∼60 nm) layer of silver, which resulted in homogeneous films of good optical quality. The silver concentration of the films ranged between 1 and 11 at.%. We have analyzed in detail the influence of the silver doping and its structure in the host material on optical properties. Analysis of the measurements have helped to understand the processes taking place during silver photodissolution.

The tailoring of the composition of Ag–As–Se amorphous films using optically-induced solid state reaction between Ag and As30Se70 films

Abstract A new technique of step-by-step optically-induced solid state reaction of Ag with As 30 Se 70 amorphous films, which has allowed the design of films with exact silver concentration, is reported. The composition of the As–Se films was chosen to be As 30 Se 70 which is the most favorable for optically-induced solid state reaction, because it yields homogeneous photodoped products. The host As 30 Se 70 films were photodoped by consecutive dissolving thin (∼20 nm) layers of silver and resulted in homogeneous films of good optical quality. The silver concentration of homogeneous samples ranged between 1 and 21 at.%. We have analyzed in detail the influence of the silver doping in the host material on optical and thermal properties, and its structure. The photodoped films produced a single-phase homogeneous material up to 21 at.% of Ag. There is evidence of Se–Se bonds breaking in photo-doped materials with increasing silver doping. Results of all three analytical techniques have helped to understand the processes taking place during silver photodissolution.

Changing the composition of Ag-As-S amorphous films using photo-induced solid state reaction

Abstract The technique of step-by-step optically-induced solid state reaction of Ag into As33S67 amorphous films, which has allowed the design of films with known silver concentrations, is reported. The host, As33S67 films, were photo-doped by consecutive dissolution of a 10 nm layer of silver, which resulted in a single layer film of optical quality as measured by optical transmissivity. The silver concentration of the samples ranged between 1 and 41 at.%. Such Ag containing films cannot be prepared directly by vacuum evaporation from AgAsS glasses due to the phase separation during evaporation process. We analyzed the affect of the silver doping in the host material on optical, thermal properties, and its structure by means of optical spectroscopy, temperature-modulated differential scanning calorimetry, and Raman spectroscopy, respectively. Optically-induced silver dissolution led to a formation of the solid solutions in above mentioned concentration range, connected with a decrease of –S–S– bonds due to their solid state reaction with migrating silver ions. The films with a silver content close to 25 at.% had the structure of stoichiometric AgAsS2. There is evidence of As–As bond formation in photo-doped materials with a silver content >40 at.%. Results of all analytical techniques we used have helped to understand the processes taking place during silver photo-dissolution.

Photostructural changes in some ternary Ge-Sb-S chalcogenide layers

The changes of optical transmission and of the index of refraction were studied in flash evaporated Ge-Sb-S layers. Photobleaching, photodarkening and photoinduced crystallization were observed depending on the composition of layers. The effects are qualitatively explained using the idea of photoinduced atoms and/or chemical bonds rearrangement.

Electrical conductivity of Agx(As40Se60)100−x bulk glasses

Abstract The samples of Ag x (As 40 Se 60 ) 100− x ( x =1–30) bulk glasses were prepared by a standard melt-quenching technique. Thermal and electrical properties were studied on the prepared glasses. Temperature-modulated differential scanning calorimetry was used to measure glass transition, cold crystallization and melting temperatures of the prepared samples. Electrical transport properties were studied by an impedance spectroscopy and dc conductivity measurements. Activation energies of the conductivity were calculated from Arrhenius plots. One-semicircle impedance spectra were found for all the glasses studied except that with 9 at.% of silver. For this sample impedance spectra with two semicircles were obtained. This phenomenon is discussed in the terms of Bauerle’s easy path theory. The compositional dependence of the conductivity showed an increase of the conductivity with increasing silver content.

Structure and photoinduced changes in As-S-Te bulk glasses and amorphous layers

Bulk glasses and thin layers from the system (As 0.33 S 0.67 ) 100-x Te x , where x = 0. 1, 5, 10, were prepared, and the photoinduced changes that they exhibit were studied. From the spectral dependence of the refractive index, the dielectric constant, e∞, the single oscillator energy, E o . and the dispersion energy. E d were calculated using the Wemple-DiDomenico equation. The changes that occur in these quantities as a result of the addition of Te to the glass, or of illumination, are explained on the basis of the different polarization of As and S atoms in comparison with the larger Te atoms, together with changes in coordination and photoinduced changes in the optical gap E opt g The redistribution of chemical bonds that arises from Te addition and/or illumination has been determined using IR and Raman spectroscopy. Addition of Te and/or exposure causes increased ordering of the structure as a result of the increase in heteropolar bonds concentration.