Optical properties and structure of As-Ge-Se thin films

Thin chalcogenide films with compositions As₁₀Ge₂₂.₅Se₆₇.₅ and As₁₂Ge₃₃Se₅₅ have been investigated. Optical constants and thicknesses of these films were obtained from transmission spectra. Structure of initial bulk glasses and films were investigated by Raman spectroscopy. Both films are estimated to have high values of the nonlinear refractive index

Polyassociative thermodynamical model of A²B⁶ semiconductor melt and phase equilibrium in Cd-Hg-Te system: 3. Optimization of the thermodynamical functions of the model and quasi-binary structural diagram of Cd-Hg-Te system

Within the frames of the model of the polyassociative solutions the comparative analysis was performed of the formation parameters of multi-atom complexes in CdTe and Hg-Te systems. It was shown, that thermodynamical properties of the studied systems can be described in the supposition of the presence in the liquid phase of the ATe, A₂Te₃, ATe₂, A₂Te (A = Cd, Hg) and free Te, Cd, Hg atoms. In accordance with the model of polyassociative solutions the data on p–T–x equilibrium in the region of quasi-binary cross-section of Cd-Hg-Te system structural diagram were obtained. It was shown, that the mixing effects in the three-component liquid phase are satisfactorily described by the formation of CdHgTe and CdHgTe₃ associates. The good correspondence of the calculations and experiment in the high temperature part of the Cd-Hg-Te system structural diagram was achieved

Вплив поверхні на спектри електровідбивання n-Si(110) та їх поляризаційну анізотропію

The electro-reflectance spectra, including their polarization dependencies were analyzed for n-Si(110) in the energy range of 2.9-3.8 eV. Based on the optical anisotropy of electro-optical effect, two contributions originated from a surface, (isotropic part relates to the linear electro-optical effect which inherent for (110) surface) and bulk, (anisotropic part relates to the Franz–Keldysh effect) were identified and separated. The presence of such extreme is explained by the zero value of the electron wave function on the surface and (or) the structure gettering of the free carriers.Проаналізовано спектри електровідбивання, включаючи їх поляризаційні залежності, для n-Si (110) в енергетичному діапазоні 2,9-3,8 еВ. Були ідентифіковані та відокремлені два внески, що випливають із поверхневої (ізотропна частина відноситься до лінійного електрооптичного ефекту, властивого для (110) поверхні) та об'ємної складових (анізотропна частина стосується ефекту Франца - Келдиша) на основі оптичної анізотропії електрооптичного ефекту. Наявність такої крайності пояснюється нульовим значенням функції електронної хвилі на поверхні та (або) структурним гетеруванням вільних носіїв

Raman scattering in sulphide glasses

Raman spectra of two ternary glasses of composition Ge₅As₃₇S₅₈ and As₄Ge₃₀S₆₆ have been investigated. An influence of addition of third element on the spectra of binary glasses has been studied by comparison with spectra of two binary glasses of composition Ge₃₃S₆₇ and As₄₀S₆₀. Glass structure and phase separation effects are discussed

The boson peak and the first sharp diffraction peak in (As2S3)x(GeS2)1–x glasses

The parameters of the boson peak (BP) and the first sharp diffraction peak (FSDP) in (As2S3)x(GeS2)1x glasses measured using high-resolution Raman spectroscopy and high-energy synchrotron X-ray diffraction measurements are examined as a function of x. It has been found that there is no correlation between the positions of BP and FSDP. The BP position shows a nonlinear composition behavior with a maximum at about x = 0.4, whereas the FSDP position changes virtually linearly with x. The intensities of both BP and FSDP show nonlinear composition dependences with the slope changes at x = 0.4, although there is no direct proportionality. Analysis of the partial structure factors for the glasses with x = 0.2, 0.4 and 0.6 obtained in another study has shown that the cation-cation atomic pairs of Ge–Ge, Ge–As and As–As make the largest contribution to FSDP, where the Ge–Ge and Ge–As pairs are dominant

Mid-IR impurity absorption in As₂S₃ chalcogenide glasses doped with transition metals

Room temperature IR impurity absorption spectra in 1 4000 7000 cm ( 4.1 - 25um ) region for chalcogenide glasses of As₂S₃ doped with chromium (0.5, 1 wt.%) and manganese (0.1, 1, 2, 5 wt.%) have been studied. The effects of chromium and manganese impurities on the transmission spectra are discussed

Raman spectra of Ag- and Cu- photodoped chalcogenide films

Raman spectra of the chalcogenide vitreous layers (As₄₀S₆₀, As₄₀S₄₀Se₂₀, As₄₀Se₆₀ ) non-doped and photodoped by Ag, Cu were measured. The spectra were analyzed in terms of a molecular model. It was ascertained, that for the spectra of photodoped As₄₀S₆₀, As₄₀S₄₀Se₂₀ layers, the shift of the main bands to the high frequency side and the appearance of the additional scattering bands in the low frequency spectral range are characteristic features. For the spectra of photodoped As₄₀S₆₀ layers, such shift and significant increase in scattering were not observed. Variations in the Raman spectra with photodoping by Ag or Cu are consistent with the supposition concerning normal covalent and coordinative bond formation between metal additives and chalcogen atoms

Structural properties of chalcogenide glasses As₂Se₃ doped with manganese

The paper presents the results of studying structural properties inherent to chalcogenide glasses doped with manganese. Investigations of the structure were carried out using Raman spectroscopy and X-ray diffraction. The function of radial distribution of atomic density and Raman spectra have been obtained and analyzed

Some peculiarities of the mechanism of irreversible photostructural transformations in thin As-S-Se layers

The present paper is concerned with the peculiarities of the mechanism of irreversible photostructural transformations in As-S-Se layers. The starting point of the irreversible photostructural transformations is the state which is determined by the conditions of the fabrication of the As-S-Se layers. It is thermodynamically unstable and differs from the structure of the glasses or annealed films. Their state is the final one for the structure of as-prepared layers changing under the influence of external factors. For the considered As-S-Se compositions the correlation of the composition dependencies for dispersion energy and optical dielectric constant of the exposed or annealed layers and structurally-dependent parameters of As-S-Se glasses: glass transition temperature Tg, relaxation enthalpy DH, heat capacity Cp, mole volume, compactness, is characteristic. Irreversible photostructural transformations are characterized by the absence of the essential influence of the diffusion processes. This is connected with the close proximity and high concentration of the non-stoichiometric molecular fragments which contain homopolar (As-As, S-S (Se-Se)) bonds. The swit­ching of the bonds with the decrease of the homopolar ones and various defects is energetically favorable. The consideration of the evolution of the number of such fragments (number of homopolar bonds) as a result of polymeric processes that take place due to the exposure influence and change the local structure of the amorphous layers towards that inherent for the glass, gives the exponential decay of their number with the increasing exposure. This is supported by the exponential decay of Raman spectra bands intensity with the exposure which correspond to the presence of molecular fragments containing homopolar bonds

Optical properties of Ge-As-S thin films

Thin Ge-As-S films have been prepared by thermal vacuum evaporation. Optical parameters and thickness values of the films have been calculated basing on transmission spectra. The dispersion dependences of the refractive index have been shown to be described well by the single oscillator model. The optical band gap width has been determined using the Tauc dependence. The non-linear optical properties of the films have been estimated basing on the data obtained.Методом термічного вакуумного випаровування отримано тонкі плівки складу Ge-As-S. Із спектрів пропускання розраховані оптичні сталі та товщини плівок. Показано, що дисперсійні залежності показника заломлення добре описуються одноосциляторною моделлю. 3а допомогою залежності Тауца визначено ширину оптичної забороненої зони. На основі отриманих даних проведено оцінку нелінійних оптичних властивостей плівок.Методом термического вакуумного испарения получены тонкие пленки состава Ge-As-S. Из спектров пропускания рассчитаны толщины пленок и оптические постоянные. Показано, что дисперсионные зависимости показателя преломления хорошо описываются одноосцилляторной моделью. С помощью зависимости Тауца определена ширина оптический запрещенной зоны. На основании полученных данных проведена оценка нелинейных оптических свойств пленок