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Cu2ZnSnS4 (CZTS) thin films deposited using direct current magnetron sputtering and sulfurized at different argon atmosphere pressures of 950, 460 and 50 mbar are studied focusing on the control of disorder degree and secondary phases. The films are in detail characterized employing X-ray diffraction, scanning electron and conductive atomic force microscopies, energy dispersive X-ray, μ-Raman spectroscopies and mappings. Such a comprehensive approach shows how the pressure variation influences morphology, structural and electrical properties of the films in submicron scale. The films sulfurized at the lowest applied pressure of 50 mbar are found to be single-phase CZTS with low disordering degree. Nevertheless, in those sulfurized at 950 and 460 mbar, Cu2-xS and ZnS secondary phases with concomitant spatial inhomogeneities are detected. At the same time, sulfurization at higher pressures enlarges the grains, which however demonstrate wide size distribution. Formation of CZTS crystal structure and secondary phases as well as acceleration of grain growth depending on pressure are interpreted and discussed.

Metamorphic InAs/InGaAs quantum dot (QD) structures have been successfully used in optoelectronics as light-emitting and sensing devices. Previous optical and photoelectrical studies showed many benefits such as the shift of the operating range in the infrared and the possibility of engineering their properties via the control of strain. However, photovoltage (PV) kinetic properties of metamorphic QD structures have not been studied yet. PV kinetics in the vertical metamorphic InAs/In0.15Ga0.85As QD and wetting layer (WL) structures compared with conventional pseudomorphic InAs/GaAs QD ones are investigated. A red-shift of the photoresponse from metamorphic QDs in comparison with pseudomorphic QDs was observed, while the PV magnitudes remain similar. Moreover, time-dependent PV measurements reveal faster increase and decay rates in both the metamorphic samples. At the same time, all the structures reveal a non-monotonous kinetics. This kinetics is explained by an unwanted PV component generated in the interface of n+-GaAs buffer to the semi-insulating GaAs substrate, causing a signal opposite to the main PV generated at the top layers of structure. We believe the findings on faster carrier kinetics in metamorphic QDs can be helpful for the development of novel efficient optoelectronic devices. Specifically, the design of metamorphic QD structure is proposed to be improved by: (i) minimizing strain-related defects, (ii) keeping such interface defects far from QDs, (iii) utilizing n+-GaAs substrates.

Effects of the microwave radiation on the culture of Chlamydomonas actinochloris green flagellar alga in the stationary phase of growth are studied. After exposure to radiation at the maximum dose of 125 J/g, the cell functional state worsened but all the studied parameters were restored in 20 days and in the long run found to be even better than the control indices. The data are compared with the similar ones obtained earlier for the lag phase culture. The studied sample is found to be more resistant to the irradiation than the previous one.

Optical properties of the rat head tissues (brain cortex, cranial bone and scalp skin) are assessed, aiming at transcranial light applications such as optical imaging and phototherapy. The spectral measurements are carried out over the wide spectral range of 350 to 2800 nm, involving visible, near-infrared (NIR) and short-wave infrared (SWIR) regions. Four tissue transparency windows are considered: ~700 to 1000 nm (NIR-I), ~1000 to 1350 nm (NIR-II), ~1550 to 1870 nm (NIR-III or SWIR) and ~2100 to 2300 nm (SWIR-II). The values of attenuation coefficient and total attenuation length are determined for all windows and tissue types. The spectra indicate transmittance peaks in NIR, NIR-II and SWIR-II, with maximum tissue permeability for SWIR light. The use of SWIR-II window for the transcranial light applications is substantiated. Furthermore, absorbance of the head tissues is investigated in details, by defining and describing the characteristic absorption peaks in NIR-SWIR.

We studied possibilities of a nondestructive X-ray technique for testing short-period strained GaAs-AlAs superlattices. An analysis of the quasi-forbidden 200 reflections may be used for determination of superlattice layer structure parameters and sublayer thickness. The effect of irregularity of superlattice transition region on X-ray diffraction reflection curves and elastic strains in layers was studied.

Effects of the microwave radiation on the culture of Chlamydomonas actinochloris green flagellar alga in the stationary phase of growth are studied. After exposure to radiation at the maximum dose of 125 J/g, the cell functional state worsened but all the studied parameters were restored in 20 days and in the long run found to be even better than the control indices. The data are compared with the similar ones obtained earlier for the lag phase culture. The studied sample is found to be more resistant to the irradiation than the previous one.

GaAs:Si/GaAs films heavily doped with Si were investigated by complex methods including X-ray diffractometrical measurement of diffraction maximum integral intensity for a quasi-forbidden reflection of the continuous spectrum wavelengths permitting determination of defect structure parameters, i.e. mean radius and concentration of precipitates and chemical composition violation (level of nonstoichiometry), as well as second ion mass spectroscopy (SIMS), measurements of electrophysical parameters. The level of nonstoichiometry was shown to depend on parameters of defect structure. The conclusion was drawn about interaction on point defects with precipitates enriched with silicon atoms.

An analysis of X-ray rocking curves and reciprocal space maps recorded for silicon single crystals before and after implantation with a 5×1014-cm−2 dose of 3 MeV/n nitrogen ions is presented. Silicon single crystals of orientation (100) were obtained by the Czochralski method. X-ray investigations were performed by means of a high-resolution Philips diffractometer using the characteristic Cu Kα1 radiation, and the integral reflectivities were measured with a double crystal diffractometer using the characteristic Ag Kα1 radiation. It was stated that irradiation with fast nitrogen ions can create extended defects as well as formation of nano-areas of disordered structure in the silicon crystal. An increase in the surface roughness was also determined from the grazing incidence X-ray reflectivity measurements.

Two-dimensional maps of x-ray diffuse scattering (DS) in a reciprocal space for a real crystal containing Coulomb deformation centres (clusters or dislocation loops) were calculated using a new dynamical theory developed for a crystalline media with homogeneously distributed defects. Such maps were calculated for both the fundamental, 400, as well as the quasi-forbidden, 200, reflections of x-rays (CuKα1 radiation) for a binary crystal (GaAs). They were also discovered experimentally in the GaAs films heavily doped with Si (up to 10 20 cm −3 ) by means of a Philips three-crystal diffractometer. The procedure for fitting calculated values of differential DS to the experimental data enabled not only the integral characteristics of the structure’s perfection (Debye–Waller static factor, LH , and coefficient of extinction of radiation due to additional energy losses on defects, µd )b ut also the average radius, ¯ r, and concentration, ¯

Specific features of the Laue diffraction of X-rays are considered for quasiforbidden reflections within the wavelength range between the K-absorption edges of Ga and As in a GaAs crystal. It is established that scattering for the 200 reflection is of the dynamical nature in the wavelength range where the real part of the structure factor Fr200 is zero and diffraction is determined by the imaginary part of the atomic form factor f″ (ω) alone. It is shown that the position of the minimum of the function Ri = f(λ) is sensitive to the crystal non-stoichiometry predicted by the numerical calculations within the theory taking into account both the real and the imaginary parts of the structure factor.

The research of the surface and the near-surface region of Cz-Si wafers irradiated with fast oxygen and neon ions of energy 4 MeV/u and dose 10 14 particles/cm 2 is presented. In our study several methods based on the Bragg case of X-ray diffraction using Ag K« 1 , as well as reflection high-energy electron diffraction and Nomarsky optical microscopy were used. It was • shown that implantation with fast neon ions causes larger disturbances of silicon crystal structure than irradiation with oxygen ions.

The averaged values of radii r and concentration n of microdefects which are the SiOx precipitates surrounded by dislocation loops were determined from the measured X-ray integral reflectivities of Czochralski grown silicon crystals subjected to annealing at high hydrostatic pressure (107–109 Pa) as well as from analysis of differential diffuse scattering behaviour near the Bragg angle. The values of these parameters and the Debye–Waller static factor behaviour show that process of the SiOx dissolution which usually takes place at the temperatures about 1500 K is slowed down in condition of hydrostatic pressure as comparing with treatment of such samples about 1500 K but by atmospheric pressure (P=105 Pa).

The effect of chemical treatment of porous silicon samples by HF on its photoluminescence and its evolution with time in sample aging in air is investigated. It is shown that the effect of HF on the luminescence parameters depends on the duration of the treatment and the initial photoluminescence intensity of the sample. It is found that chemical etching in HF accelerates the growth of the total luminescence intensity in aging of the sample in air. The evolution of the photoluminescence spectrum in aging of the sample in air after chemical etching can be explained within the framework of the quantum-size model of the luminescence of porous silicon.

The methods of numerical calculations based on the formulae of the X-ray dynamic scattering theory by real crystals and of the Takagi-Topin equations were used for investigation of the basic regularities of inherent to the Bragg diffraction in conditions of a strong and weak ab- sorption. The mechanisms of profile formation of a spatial intensity distribution of diffracted beams depending on an energy of radiation and on structural perfection parameters of crystals are discussed. The formulae for an analytical description of spatial intensity distribution profiles which take into account the dynamical corrections (coefficients of extinction) for coherent and incoher- ent components of the total reflectivity were used.

The near-surface layers of dislocation free silicon crystals implanted with 4 MeV/u oxygen and neon ions were investigated. The following methods: X-ray diffraction and reflectometry, reflection high-energy electron diffraction and Nomarski optical microscopy were used. The fine structural changes induced by irradiation were observed. For silicon crystal implanted with neon ions the increase of the lattice parameter and a disturbance of crystal structure were detected, whereas for silicon crystal bombarded with oxygen ions postimplantation defects on the surface were observed. For both cases the increase in the surface roughness was shown.

The structural perfection of Czochralski grown silicon crystals annealed at 1580-1620 K under hydrostatic pressure up to 10 9 Pa was investigated by X-ray diffractometry and topography supplemented by the method of absorption of infrared rays. Such treatment suppresses dissolution of oxygen-related defects. From the static Debye—Waller factor dependence on the reflection order it was concluded that large clusters or dislocation loops are the dominant type of defects for most of the samples. PACS numbers: 81.05.Cy, 81.40.—z

Silicon crystals contained copper atoms included by diffusion way during high temperature treatment have been investigated by means of X-ray transmission topography (Lang method). The studies allow us to observe the increase or decrease iai the dislocation images widths in dependence on the time of diffusin annealing. In one case, during the more prolonged decoration process a build-up of decorating particles on dislocation occurs with widening of the topographic images of this dislocation. Ιn another case (short time of decorating process) some compensation of defect deformation frelds has been noticed (shortening of tle mentioned images takes part). The obtained effects depend not only on the type of intrinsic impurities which take part in forming the Cottrell atmospheres but also on the duration of diffusion annealing. Tle observed results of interaction of dislocations with impurities have been confirmed by the studies of the integral reflectivity of decorated samples by means of the double-crystal spectrometer. PACS numbers: 61.10.—i, 61.72.Cc, 61.72.Ff, 81.40.Cd

A diffractometrical method for quantitative evaluation of structure perfection level in silicon single crystals containing various types of near surface distortions is described. The method is based on the spatial distribution analysis of the reflected intensity in the Bragg case of diffraction. To implement the proposed approach one has to satisfy the condition of the so-called low X-ray absorption because in this case the penetration depth of diffracted radiation exceeds the corresponding value of extinction length. It permits us to obtain a remarkable value of noncoherent reflectivity due to defects placed in deep (on the extension of absorption length) regions of a crystal and therefore, to increase the sensitivity of scattering for low distortions of crystal lattice. Using the method described here the extension of various disturbed layers as well as the level of the static Debye-Waller factor of a crystal can be determined. The effect of surface distortions caused by mechanical treatment and the influence of the following thermal annealing as well as irradiation by high energy protons on the defective structure of the samples were investigated. PACS numbers: 81.40.—z, 61.10.-i

In their recent paper, Wang and Su (2015 Eur. J. Phys. 36 055010) acquainted readers with a solution to a problem about the optimal shape of an object for generating a maximum gravity field at a given point in space. After applying the variational principal and the Euler–Lagrange equation they obtained the shape for two-, three- and arbitrary n-dimensional cases. We are convinced that the problem is interesting enough to consider it with students. In this Comment we will try to present an easier way to solve it for the three-dimensional space.

The fluorescence spectra of the porous silicon modified by water solutions of biologically active materials and materials of biological origin are recorded as well as the fluorescence spectra of the porous silicon modified by lecithin monolayers grown on the surface of water solutions of the biologically active materials. The analysis of the obtained spectra made it possible to conclude on the effect of the studied materials on the content of ROS.

Effect of the microwave irradiation on the subsequent development of the Chlamydomonas actinochloris culture is studied. The number of cells in the suspension was controlled and photoluminescence measurements were performed for 25 days to estimate the functional state of the cells. The exposure at a dose of 80 J/g is shown to negligibly affect the green alga, whereas the 122 J/g dose led to deterioration of the functional state and, thereafter, to the death of most cells. However, the survivors intensively developed, the culture restored the normal state for 20 days, reached and later even left behind the control sample in development.

The effect of high temperature (up to 1120 ° C)—high pressure (up to 1.1 GPa) treatment mr tle resulting defect structure of preannealed (450-725°C, up to 96 hours) Czochralski grown Si crystals was studied by X-ray diffraction. The values of the Debye-Waller static factor and of the root-mean-square atomic dispalacement due to defects were determined for various Laue reflections. Well-defined development of the cluster like defect structure after high temperatnre pressurization depending to a substantial extent mi the preannealing conditions was observed. PACS numbers: 61.70.-r, 81.40.-z

Sensitivity of X-ray integral reflectivity of GaAs single crystal to a degree of structure distortions was established to grow considerably in the Bragg diffraction case when tle characteristic Ag Κ, 1 line is changed for more hard white radiation. In effect, the absorption length essentially exceeds the extinction length what results in enlancement of incoherent scattering. Measurements of X-ray integral reflectivity coordinate dependence b y single crystal spectrometer permitted to determine the mean level of crystal 1attice distortion as well as the degree of structure homogeneity of a sample with dislocations. The Debye-Waller static factor value vas estimated from X-ray integral reflectivity magnitudes for the 800 reflection of white radiation.

Determination of the integral claracteristics of structural perfection of a real crystal (i.e. Debye-Waller's static factor e -L and coefficient of absorption μd s due to diffuse scattering) is especially expedient using the suitably selected wavelengths of the X-ray continuous spectrum by investigation of the thickness I(t), coordinate I(x) as well as amplitude I(W) dependencies of intensities at Laue or Bragg diffraction. Here W is an amplitude of weak ultrasound vibrations excited in a sample for suppression of tle Bragg component of reflectivity. PACS numbers: 81.40.—z, 61.66.Bi, 61.72.Dd

The influence of microwave emission on the Vallisneria spiralis L. photoluminescence (PL) is studied. It is found that the irradiation leads to degradation of all the luminescence spectrum bands. It is shown that the influence on the chlorophyll PL at 715-735 and 800 nm is not limited by accompanied temperature effect. The degradation of PL has a temperature threshold at the thermal treatment. The 725 nm luminescence band of chlorophyll is shifted to short waves at both the irradiation and thermal treatment. The shift dependence from the irradiation dose and temperature is non-monotonous.

The amplitude dependences of the integral reflectivity (IR) Ri(W) of perfect silicon crystals distorted by shear short wave ultrasonic vibrations are investigated for high order reflections of AgKβ, AgKα1 radiations. Transition to the kinematical regime of diffraction is obtained for high ultrasound amplitudes both, in the Laue and in the Bragg case of diffraction. The ratios of the integral reflectivities measured in the initial and distorted state of a crystal are in agreement with the theory developed formerly. The influence of structural defects on the transition of the IR to the kinematical regime is studied, too. [Russian Text Ignored.]

The influence of large dislocation loops and clusters (with radius rd of the order of extinction length Λ) in dislocation-free silicon crystals grown by the Czochralsky-method on the thickness dependence of the total integral reflectivity Ri as well as on its Bragg's RB and diffuse RD components is investigated by variation of the X-ray wavelength (MoK, CuK-radiation) and of the order of Laue diffraction. For such defects diffuse scattering is concentrated near the reciprocal lattice point (RLP). Integral intensities are measured by means of the Bragg-Laue double crystal spectrometer in the positions (n, −n) and (n, −2n). The components RB and RD are determined using the formula of the dynamical theory of X-ray scattering in crystals with homogeneously distributed defects and the values of diffraction parameters i.e. the static Debye-Waller's factor L, and coefficient absorption due to diffuse scattering μds measured under conditions of weak absorption where the interfere influence of dynamical effects is negligible. The sensitivity of Ri to large defects is shown to increase at the expence of growing of the relative contribution of the RD component by transition to reflection of higher orders as well as by using of harder short-wavelength radiation. The ratio RD/Ri does not depend on the crystal thickness under conditions of strong absorption what conforms the arising of the dynamical regime for the diffuse component. This effect is absent for small (rd ≫ Λ) defects. The parameter L is shown to be more sensitive to the presence of large defects than μds. [Russian Text Ignored].

Atmospheric air pollution can cause the oppression of the placentae fine structures development and of the adaptive abilities. These changes and its expression co-related with the level of air pollution.

The effect of the net plane curvature on the X-ray intensities at Laue diffraction is investigated by means of a thermal gradient normal to these planes. By contrast to previous works, a good agreement is obtained between the measured and calculated values of the normalized intensities as well as of their most important parameters, namely the absorption and migration factors. The conclusion is drawn that Penning and Polder's theory satisfactorily describes the diffraction phenomena in crystals where the net planes are subjected to curvature only. [Russian Text Ignored].

The existence of a linear function of the integral intensity logarithm versus the sample thickness is shown by investigation of the X-ray interference transmission in an elastically bent thin crystal. The parameters of that function namely the effective interference coefficient of absorption μie and the factor In C describing the diffraction condition failure by deformation are determined depending on the sign and level of strain ϵ. μie as a function of t has specific features. It increases and decreases regarding to the meaning of the photoelectric absorption coefficient μ0, reaches a minimum and maximum for ϵ ≥ 0 and ϵ ≤ 0, respectively, and after that tends again to μ0. Such peculiarities of the μie functions may be explained on the basis of suppression of one of the wave fields in a thin crystal by strain. [Russian Text Ignored].

A strict dynamical theory of radiation scattering in defect crystals is developed involving no arbitrary assumptions. Final theoretical expressions are obtained for the case of Laue-diffraction in monocrystals containing homogeneously distributed defects, in particular Coulomb-like defects (clusters, dislocation loops). The theory gives an unified description of the thickness dependences of intensity scattering both, for thin and thick crystals, and predicts an effect of anomalous transmission of diffuse background in thick crystals. Experimental investigations on O- or Cu-doped Si-monocrystals are carried out which confirms the theory. [Russian Text Ignored].

The behaviour of the Laue diffracted intensities has been studied as a function of the value of departure of the diffraction net plane from the normal position to the surface of an elastically strained crystal. These intensities and the interferencial coefficient of absorption depend on the deformation efficiency parameter Z in a more complicated way than it has been predicted by the theories of Kato and Penning and Polder. The qualitative agreement of the behaviour of the experimental curves, obtained at different μt, with Kato's theory is established. The necessity is suggested to take into account the effect of the net planes fanning-out on the Laue diffraction for an elastically bent crystal. [Russian Text Ignored].

The Borrmann effect peculiarities in elastically bent silicon crystals containing structural defects appearing as a result of decay of oxygen solid solution are investigated by means of a double-crystal spectrometer. Linearity of the thickness dependences of the integral intensity logarithms In IR = f(t) at fixed level of elastic strain ϵ is established in such samples. This fact allows to determine the most important parameters μi and α describing respectively the absorption and scattering of intensity IR in an elastically bent crystal. The effect of non-additive influence of the localized and distributed distortions of lattice periodicity as well as the sensibility attenuation of IR to elastic strain in real samples with respect to perfect crystals are explained on the basis of decreasing of the effective volume scattering the radiation dynamically. [Russian Text Ignored]