[Show abstract][Hide abstract] ABSTRACT: A new approach to analyzing the X-ray diffraction spectra of multilayer structures is described. This approach is based on information on the layer growth time. As compared to the standard analysis, the number of variable parameters decreases. The stability and rate of convergence of fitting a calculated spectrum to an experimental spectrum increase in the case of a large number of layers and little-information experimental data. The approach is executed by imposing relations on the model parameters during the calculation of spectra using the Bruker DIFFRAC.Leptos software package. A multilayer SiGe/Si structure is used to compare the new approach and the standard procedure of analysis. The correctness of the new approach is supported by a comparison with the experimental data obtained by secondary-ion mass spectrometry and transmission electron microscopy. The advantages and limitations of the proposed method are discussed.
[Show abstract][Hide abstract] ABSTRACT: In the present work features of antimony (Sb) segregation in SiGe heterostructures grown by molecular beam epitaxy are investigated. Dependences of the segregation strength on growth temperature, composition and elastic strains are obtained. It is shown that growth conditions and parameters of the structure exert an interrelated impact on the impurity segregation: the influence of the structure parameters depends on growth temperature. Moreover, the alloy composition is found to be a much more significant factor than the elastic strains in SiGe layers. Obtained dependences of Sb segregation on growth conditions and structure parameters were used for formation of selectively doped SiGe heterostructures.
Journal of Crystal Growth 01/2014; 396:66–70. · 1.55 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Model Al/C60/ITO sandwich devices were fabricated, where Al is a magnetron sputtered aluminum layer (top electrode); C60 is a buckminsterfullerene layer routinely deposited by thermal evaporation in vacuum; and ITO is an indium tin oxide layer (bottom electrode). These devices demonstrate weak rectification in the dark and almost negligible photovoltaic activity under illumination, if polyethyleneterephthalate (PET) is used as substrate. If the substrate is glass, inversion of rectification occurs, accompanied by a rather more pronounced photovoltaic effect (in the reverse direction, too) than in their Al/C60/ITO/PET counterparts. Secondary ion mass spectroscopy (SIMS) with depth-profiling suggests that this effect is associated with the differences in the chemical composition of the top Al/C60 interface in devices on PET and on glass. Such differences result from migration of admixtures from the substrate towards the top electrode. Since (photo)electrical properties of the devices reflect the dominating contribution of one of the two interfaces (top Al/C60 and bottom C60/ITO), rectification can be reversed by amending either interface. This fact is to be taken into account when comparing efficiency of multilayer photovoltaic cells (e.g., with a heterojunction) on different substrates.
[Show abstract][Hide abstract] ABSTRACT: A study of vertical transport in δ-doped SiGe/Si heterostructures is presented. An asymmetrical triple barrier structure was grown with a δ-layer of boron impurity in the center of a narrow quantum well. The growth procedure was followed by conventional processing including photolithography, plasma etching and magnetron sputtering. Secondary-ion mass-spectroscopy depth profiling and high resolution x-ray diffraction were used to control the as-grown structure. The conductance of the structure was measured at liquid helium temperature and analyzed. All pronounced resonances were identified. The resonant feature near 60 mV is attributed to impurity-assisted tunneling, which is supported by calculation of the binding energy of the acceptor in the narrower quantum well.
Physica E Low-dimensional Systems and Nanostructures 01/2014; 57:42–46. · 1.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A new variant of depth profiling for thin-film fullerene-containing organic structures by the method of time-of-flight (TOF) secondary ion mass spectrometry (SIMS) on a TOF.SIMS-5 setup is described. The dependence of the yield of C60 molecular ions on the energy of sputtering ions has been revealed and studied. At an energy of sputtering Cs+ ions below 1 keV, the intensity of C60 molecular ions is sufficiently high to make possible both elemental and molecular depth profiling of multicomponent (multilayer) thin-film structures. Promising applications of TOF-SIMS depth profiling for obtaining more detailed information on the real molecular composition of functional organic materials are shown.
[Show abstract][Hide abstract] ABSTRACT: In this publication, we report the results of studying a multilayerd nonperiodic SiGe/Si structure by the methods of X-ray diffractometry, grazing-angle X-ray reflectometry, and secondary-ion mass spectrometry (SIMS). Special attention is paid to the processing of the component distribution profile using the SIMS method and to consideration of the most significant experimental distortions introduced by this method. A method for processing the measured composition distribution profile with subsequent consideration of the influence of matrix effects, variation in the etching rate, and remnants of ion sputtering is suggested. The results of such processing are compared with a structure model obtained upon combined analysis of X-ray diffractometry and grazing-angle reflectometry data. Good agreement between the results is established. It is shown that the combined use of independent techniques makes it possible to improve the methods of secondary-ion mass spectrometry and grazing-incidence reflectometry as applied to an analysis of multilayered heteroepitaxial structures (to increase the accuracy and informativity of these methods).
[Show abstract][Hide abstract] ABSTRACT: The effects of the growth temperature, composition, and elastic strains in separate layers on the segregation of antimony are studied experimentally for stressed SiGe structures grown by molecular beam epitaxy. It is established that the growth conditions and parameters of the structures exert an interrelated influence on the segregation of Sb: the degree of the influence of the composition and elastic stresses in the SiGe layers on Sb segregation depends on the growth temperature. It is shown that usage of a method previously proposed by us for the selective doping of silicon structures with consideration for the obtained dependences of Sb segregation on the growth conditions and parameters of the SiGe layers makes it possible to form SiGe structures selectively doped with antimony.
[Show abstract][Hide abstract] ABSTRACT: The results of experimental studies of the effect of rapid thermal annealing on low-barrier diode structures used in the fabrication of microwave detectors for imaging arrays are indicative of an increase in the effective barrier height. Assuming that this effect is related to the diffusion spreading of the silicon δ-doped layer, which determines charge transport in the modified diode, a theoretical model is developed and the diffusion coefficient for silicon in the near-surface region of gallium arsenide (D ≈ 2 × 10−14 cm2/s at 600°C) is estimated. A comparison with published data makes it possible to assume that diffusion in the near-surface layers is greatly facilitated compared to that in the bulk. It is suggested that the cause of acceleration of the diffusion can be a high electric field formed by the charged plane of the detector and it can also be related to an increased density of defects near the surface. The practical result consists in the emerging possibility of increasing (within a certain range) the effective barrier height in the grown structures, which will make it possible to adapt the parameters of low-barrier diodes to the optimal value in order to obtain sensitive detectors.
[Show abstract][Hide abstract] ABSTRACT: We report the results of the first experiments on the growth of indium
nitride films by electron cyclotron resonance plasma-enhanced metal
organic chemical vapor deposition. Discharge sustained by the radiation
of a technological gyrotron with a frequency of 24 GHz and power up to 5
kW was used to provide active nitrogen flow. The use of higher frequency
microwave radiation for plasma heating provides a higher plasma density,
and more active nitrogen flow. Mirror-smooth homogeneous hexagonal InN
films were grown on ittria-stabilized zirconia and sapphire substrates.
It was shown that single-crystal InN films can be grown on
Al2O3 (0001) substrates if a double buffer layer
of InN/GaN is used. The growth rate of 1 μm/h was demonstrated in
this case. Film properties are studied by optical and electron
microscopies, secondary ion mass spectroscopy, X-ray diffraction, and
Japanese Journal of Applied Physics 08/2013; 52(8). · 1.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: GaAs-based heterostructures with Ge and Ge/InGaAs quantum wells are grown by laser-assisted sputtering. Structural and optical studies of the heterostructures are carried out. A broad photoluminescence line is observed in the wavelength range from 1300 to 1650 nm. The line corresponds to indirect transitions in the momentum space of the Ge quantum wells and to transitions between the In0.28Ga0.72As and Ge layers, indirect in coordinate space, but direct in momentum space.
[Show abstract][Hide abstract] ABSTRACT: The fabrication technology and properties of light-emitting Si structures codoped with erbium and oxygen are reported. The layers are deposited onto (100) Si by molecular beam epitaxy (MBE) using an Er-doped silicon sublimation source. The partial pressure of the oxygen-containing gases in the growth chamber of the MBE facility before layer growth is lower than 5 × 10−10 Torr. The oxygen and erbium concentrations in the Si layers grown at 450°C is ∼1 × 1019 and 1018 cm−3, respectively. The silicon epitaxial layers codoped with erbium and oxygen have high crystal quality and yield effective photoluminescence and electroluminescence signals with the dominant optically active Er-1 center forming upon postgrowth annealing at a temperature of 800°C.
[Show abstract][Hide abstract] ABSTRACT: YBa2Cu3O7 − δ high-temperature superconductor targets subjected to ion-plasma sputtering in a magnetron-sputtering system are studied by X-ray diffraction analysis and secondary ion-mass spectrometry. It is found that dc magnetron sputtering is accompanied by diffusive oxygen depletion and restructuring of the target surface caused by radiation and heat effects of bombarding ions. It is assumed that these changes in the target are responsible for a decrease in the growth rate of YBa2Cu3O7 − δ films.
[Show abstract][Hide abstract] ABSTRACT: A TOF.SIMS-5 by ION-TOF operating with pulsed 25 keV Bi+ for
analysis and 2 keV Cs+ for sputtering was used to study depth
compositional changes in near-surface layers of permalloy (iron-nickel)
blades after treatment by pulsed nitrogen plasma directly in sealed reed
switches. The formation of 350 nm-thick oxy-nitride coating in the
contacting region of the blades was observed. It was found that the
origin of this coating cannot be explained just by nitrogen and oxygen
diffusion inside the treated material. Rather, cathode sputtering and
re-deposition of sputtered products, thermal decomposition of nitrides
and oxides along with sputter-induced surface roughening can also
contribute in the formation of the modified layers.
[Show abstract][Hide abstract] ABSTRACT: The depth resolution function of the TOF.SIMS-5 secondary ion mass spectrometer has been studied for several types of analyzed structures under different experimental conditions. A numerical algorithm for calculating the depth distribution profile of an element for a given structure model taking into account ion mixing, induced roughness, and information depth has been realized. The values of the depths of the thin near-surface layers (δ-layers) of Ge in a Si matrix and Si in a GaAs matrix were determined by fitting the calculated profiles to experimental ones by varying parameters of the resolution function. It is shown that determination of the depth of the δ-layer from the peak position on the experimental profile yields a large systematic error, account of which noticeably increases the accuracy of estimating the delta-layer’s position.
Journal of Surface Investigation X-ray Synchrotron and Neutron Techniques 07/2012; 6(4). · 0.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Freestanding absorption filters based on Mo/Si and Mo/ZrSi2 are tested under conditions of long-term heating in vacuum in the temperature range 700–1000°C. The effect of high temperatures on the optical and structural characteristics of the films is studied. The critical thermal loads at which filters maintain their properties during many hours of testing are estimated. The mechanisms for the degradation of filter characteristics upon annealing are determined by means of secondary ion mass spectrometry (SIMS) data and optical measurements.
Journal of Surface Investigation X-ray Synchrotron and Neutron Techniques 05/2012; 6(3). · 0.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Manganese diffusion during annealing of structures with InGaAs/GaAs quantum wells and a Mn delta-layer is investigated by photoluminescence and secondary ion mass spectrometry. Annealing at 365–425°C results in quenching of the photoluminescence intensity for the quantum well nearest to the Mn deltalayer, due to Mn diffusion into the quantum well. The penetration of Mn and In into the GaAs coating/cover layer is discovered. Near the surface the profiles of these elements are similar.
Journal of Surface Investigation X-ray Synchrotron and Neutron Techniques 05/2012; 6(3). · 0.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: a b s t r a c t A new approach for producing high-purity silicon with isotopic enrichment of 28 Si isotope is reported. The methods of centrifugal enrichment were modified to obtain the initial gaseous silicon tetrafluoride with a record-breaking enrichment of 0.99999664(11) with respect to 28 Si. The effective conversion of silicon tetrafluoride into elementary silicon with minimal isotopic dilution was achieved in an electron cyclotron resonance discharge plasma, sustained by gyrotron microwave radiation with a frequency of 24 GHz. We have experimentally demonstrated the deposition of the layers of microcrystalline 28 Si with enrichment of 0.999986 ± 0.000003, which is the best result at the present time.
Solid State Communications 01/2012; 152:455-457. · 1.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: An original approach to selective doping of Si by antimony (Sb) in molecular beam epitaxy (MBE) is proposed and verified experimentally. This approach is based on controllable utilization of the effect of Sb segregation. In particular, the sharp dependence of Sb segregation on growth temperature in the range of 300–550 °C is exploited. The growth temperature variations between the kinetically limited and maximum segregation regimes are suggested to be utilized in order to obtain selectively doped structures with abrupt doping profiles. It is demonstrated that the proposed technique allows formation of selectively doped Si:Sb layers, including delta (δ-)doped layers in which Sb concentrations can be varied from 5 × 1015 to 1020 cm−3. The obtained doped structures are shown to have a high crystalline quality and the short-term growth interruptions, which are needed to change the substrate temperature, do not lead to any significant accumulation of background impurities in grown samples. Realization of the proposed approach requires neither too low (<300 °C), nor too high (>600 °C) growth temperatures or any special equipment for the MBE machines.
Journal of Applied Physics 06/2011; 109(11):113533-113533-7. · 2.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A technique for fabrication of freestanding multilayers which are able to be used as optical elements in the soft X-ray and EUV ranges is reported. Two types of transmission mode elements have been developed: phase retarders for the aims of soft X-ray polarimetry and thin film spectral filters. A variety of phase retarders on the base of Cr/Sc, Cr/C, V/B4C and W/B4C freestanding multilayers were designed for a spectral region of "water window" (lambda~ 2-4.5nm) 2 - 4.5 nm). The possibility to yield the phase shift between s- and p-polarizations as high as 90Âº at equal transparencies of these polarizations of 0.4% was experimentally demonstrated with Cr/Sc phase retarder close to the Sc L-edge of absorption (lambda = 3.11 nm). The set of freestanding absorption filters Cr/Sc, Mo/C, Zr/Si, Zr/Al with spectral windows within 2.2 to 22 nm wavelength range was developed for the aims of hot plasma diagnostics. We also fabricated Al/Si structures with supported mesh, which are transparent in the range lambda = 17 - 60 nm, for application in the sun astronomy. The sample of 160 mm in diameter Mo/ZrSi2 spectral purity filters with transparency of 70% (lambda = 13 nm) was fabricated as the probable component part of industrial EUV lithography tool. The preliminary testing of heat load withstandability was fulfilled for a number of freestanding multilayers consisting of Si, Zr, Mo and silicides of both metals. It was found that Mo/ZrSi2 structure is the challenge to withstand intensive heating up to 800 - 850°C.