The initial stages of growth of barium zirconate titanate and barium stannate titanate ferroelectric films on single-crystal sapphire and silicon carbide are studied for the first time. The choice of substrates is dictated by the possibility of using such structures in ultra-high frequency devices. The growth of discontinuous BaZrxTi1–xO3 films is found to be mediated by the gas phase mass transport mechanism in the studied temperature range. For deposition of BaSnxTi1–xO3 films, the mechanism of mass transport switches at ~800°C from surface diffusion to gas phase diffusion; also, the films deposited on sapphire and silicon carbide have considerably different elemental composition. The formation of an intermediate SiO2 layer is noted on silicon carbide during the growth of oxide films on this substrate, its thickness depending on the deposition temperature.

AbstractThe initial stages of growth of barium zirconate titanate and barium stannate titanate ferroelectric films on single-crystal sapphire and silicon carbide are studied for the first time. The choice of substrates is dictated by the possibility of using such structures in ultra-high frequency devices. The growth of discontinuous BaZr_ x Ti_1– x O_3 films is found to be mediated by the gas phase mass transport mechanism in the studied temperature range. For deposition of BaSn_ x Ti_1– x O_3 films, the mechanism of mass transport switches at ~800°C from surface diffusion to gas phase diffusion; also, the films deposited on sapphire and silicon carbide have considerably different elemental composition. The formation of an intermediate SiO_2 layer is noted on silicon carbide during the growth of oxide films on this substrate, its thickness depending on the deposition temperature.

Методом "многостоповой" времяпролетной масс-спектрометрии исследован механизм радиационных повреждений молекул глицина, находящихся в газовой фазе, при взаимодействии с ионами He2+ с энергией Ep = 4 keV/a.m.u. Впервые измерены относительные сечения различных элементарных процессов, происходящих при однократных столкновениях молекул глицина с ионами. Обнаружено различие в фрагментации промежуточных двухзарядных ионов, формирующихся в процессах захвата одного электрона с ионизацией и двухэлектронного захвата, что объясняется разницей в энергии возбуждения молекулярных ионов. DOI: 10.21883/PJTF.2017.07.44470.16531

The initial stages of the growth of ferroelectric barium strontium titanate films on single-crystal silicon carbide substrates have been studied for the first time. The choice of a substrate with high thermal conductivity has been due to the possibility of applying these structures in powerful microwave devices. The temperature ranges separating the mechanism of the surface diffusion of deposited atoms from the diffusion via a gaseous phase during the growth of multicomponent films have been determined. The studies show that the mass transfer by means of surface diffusion leads to the formation of small-height nuclei that cover a large area of the substrate, whereas the mass transfer via a gaseous phase leads to the formation of a “columnar” islandtype structure with small percentage of covering the substrate and larger island heights.

Измерены абсолютные величины дифференциальных сечений рассеяния быстрых частиц, образовавшихся в процессах захвата одного или двух электронов у атомов Ar ионами He2+ с кинетической энергией 6 keV в диапазоне углов рассеяния 0-2.5o. Определены сечения процессов захвата и захвата с ионизацией как функции параметра удара. Проведено сопоставление вероятностей осуществления исследуемых процессов с распределением электронной плотности различных оболочек в атоме-мишени. Сделана оценка применимости моделей экранированных кулоновских потенциалов взаимодействия для описания рассеяния перезарядившихся частиц. DOI: 10.21883/PJTF.2017.02.44190.16419

The method of "multistop" time-of-flight mass spectrometry has been used to study the mechanism of radiation damage to glycine molecules in the gas phase upon their interaction with He2+ ions with energy E (p) = 4 keV/amu. The relative cross sections of various elementary processes occurring in single collisions of glycine molecules with the ions were measured for the first time. A difference was found between the fragmentations of intermediate doubly charged ions formed in capture of a single electron with ionization and in two-electron capture, which is accounted for by the difference between the excitation energies of molecular ions.

The absolute differential cross sections of scattering of fast particles formed in processes with capture of one or two electrons from Ar atoms have been measured for 6-keV He 2+ ions in the interval of scattering angles within 0°–2.5°. The cross sections of electron capture and electron capture with ionization have been determined as functions of the impact parameter. The probabilities of these processes are compared to the distribution of electron density in various shells of target atoms. Applicability of the models of screened Coulomb interaction potentials to description of the scattering of recharged particles is assessed.

Впервые исследованы начальные стадии роста сегнетоэлектрических пленок титаната бария-стронция на подложках монокристаллического карбида кремния. Выбор подложки, обладающей высокой теплопроводностью, обусловлен возможностью применения данных структур в мощных сверхвысокочастотных устройствах. Определены диапазоны температур, разделяющие механизм поверхностной диффузии осаждаемых атомов от диффузии через газовую фазу при росте многокомпонентных пленок. Исследования показали, что массоперенос посредством поверхностной диффузии приводит к формированию зародышей малой высоты, покрывающих большую часть подложки, тогда как массоперенос атомов через газовую фазу приводит к образованию "столбчатой" островковой структуры с малым процентом покрытия подложки и большей высотой островков. А.В. Тумаркин и А.А. Одинец выражают благодарность за финансовую поддержку РФФИ (проект 16-29-05147 офи\_м) и Минобрнауки России (государственное задание N 3.3990.2017.ПЧ). DOI: 10.21883/FTT.2017.12.45230.157

The relative cross sections of elementary processes occurring in single collisions of tryptophan molecules in the gaseous phase with He2+ ions with energy 4 keV/u are measured using time-of-flight mass spectrometry for studying the mechanism of radiation damage of amino acid molecules. The fragmentation channels for intermediate singly and doubly charged tryptophan molecular ions formed during one-electron capture, two-electron capture, and electron capture with ionization are investigated. Significant difference is observed in the mass spectra of fragmentation of intermediate doubly charged ions formed during the capture with ionization and double capture, which is associated with different energies of excitation of {C11H12N2O2}2+* ions.

The initial stages of growth of ferroelectric films of barium strontium titanate BaSrTiO 3 on singlecrystal sapphire substrates have been experimentally investigated as a function of the deposition temperature. It has been shown that, at the initial stage of the condensation of the BaSrTiO 3 film on sapphire, the temperature of the substrate determines the mechanisms of mass transfer of deposited atoms and the processes of nucleation.

We have studied the process of UV reduction of wrinkled grahpene oxide films, deposited on silicon substrate from ethanol suspension. In order to avoid destruction of graphene oxide via ozone formation from ambient air, samples were protected by argon atmosphere during UV irradiation. Using the analysis of back scattering spectra for medium energy ions, we have found that the UV irradiation mediated reduction process produced significantly decreased carbon content on the substrate surface. The decrease in the carbon content was accompanied by a smoothing of the films during reduction to graphene. We suppose that the observed effect is related to the oxidation of carbon atoms in the graphene scaffold of graphene oxide to carbon monoxide or dioxide by the oxygen from the graphene oxide (GO) itself. One has to consider this when developing a process for the preparation of graphene films using the UV-mediated reduction of graphene oxide.

The possibilities of Medium-Energy Ion Scattering (MEIS) spectrometry combined with ion channeling for the estimation of the composition of single layer graphene oxide films and produced graphene layers deposited on the surface of standard silicon substrates was investigated. It was found that the oxygen amount in the natural surface silicon oxide ranges from 2-8 times the possible oxygen content in a graphene oxide layer. This causes difficulties in the estimation of the oxygen concentration in graphene oxide deposited on such substrates. The proposed method of preliminary single hydrogen cathode surface processing in electroplating bath leads to the significant decrease of surface layer oxygen content which results in an increase in the accuracy of reduced graphene oxide composition estimation.

The absolute differential cross sections of scattering of hydrogen atoms resulting from an electron capture and an electron capture ionization are measured for collisions of 4.5- and 11-keV protons with argon and xenon atoms. The range of scattering angles is 0°–2°. From the scattering differential cross section found experimentally, the probabilities of single-electron capture and electron capture ionization as a function of the impact parameter are calculated. The dependences of the incident particle scattering angle on the impact parameter (deviation function) for interactions with Ar and Xe atoms are calculated in terms of classical mechanics using the Moliére—Yukawa potential to describe the interaction of atomic particles. Analysis is given to the probabilities of electron capture and electron capture ionization versus the impact parameter and to the distribution of the electron density on different electron shells in a target atom versus a distance to the core. It is concluded that only electrons from the outer shell of the target atom are involved in the process of electron capture ionization. The cross section of electron capture ionization is calculated in the proton energy range 5–20 keV.

X-ray diffraction (XRD) and medium-energy ion scattering (MEIS) have been used to reveal distortions in the crystal lattice of La0.67Ba0.33MnO3 (LBMO) films formed in relaxation of mechanical stresses. The LBMO films 25 nm thick have been prepared by laser deposition. The XRD and MEIS data obtained suggest that biaxially and mechanically elastically stressed LBMO layers grow coherently on LSATO substrates, whose crystal lattice parameter differs only weakly from the corresponding LBMO parameter, whereas in the bulk of manganite films grown on LaAlO3 substrates, stresses relax partially. Stresses do not relax in the LBMO interface about 4 nm thick adjoining LaAlO3. The electro- and magneto-transport parameters of partially relaxed LBMO films have been compared with those obtained for coherently grown manganite films with approximately the same tetragonal distortion of the lattice cell (a ⊥/a ‖ = 1.024–1.030; a ‖ and a ⊥ are the unit cell parameters in the substrate plane and normal to it, respectively). At temperatures substantially lower than the Curie temperature, the electrical resistivity ρ of LBMO films fits the relation ρ = ρ0 + ρ1 T 2 + ρ2(H)T 4.5; the coefficients ρ0 and ρ1 do not depend on temperature T and magnetic field, and ρ2 does not depend on temperature but almost linearly decreases with increasing magnetic field strength H. The coefficient ρ2 for partially relaxed LBMO films is substantially larger than that for coherently grown manganite layers.

The relative cross sections of processes taking place when H+ and He2+ ions with an energy of 6z keV (z is the ionic charge) capture an electron from molecules of C5H11NO2S methionine (proteogenic amino acid) and C6H13NO2 norleucine (nonproteogenic amino acid) are measured by time-of-flight mass spectrometry (a methionine molecule transforms into a norleucine molecule by substituting the CH2 group for the S heteroatom). The fragmentation pattern of resulting molecular ions is established from correlation analysis of the detection times of all fragment ions. The results are compared with experimental data for fragmentation of the same molecules ionized by electrons and photons. In these amino acids, the pattern of molecular ion fragmentation is found to depend on the type of molecule ionization. However, the detachment cross section of the COOH neutral group or residue (neutral or charged) R of a side chain of the amino acid is invariably among the largest. The relative cross sections of capture with single and double ionization of molecules are measured.

The time-of-flight mass spectrometry method is used to study processes occurring when 36-keV multiply charged Ar ions (Ar6+) capture electrons from adenine and uracyl molecules. Adenine and uracyl constitute one of two base pairs entering into the RNA composition. The fragmentation scheme of resulting molecular ions is derived by analyzing correlations between the detection times of all fragment ions. Fragmentation patterns for molecular ions resulting from molecule ionization by photons, electrons, protons, and multiply charged ions are compared.

Time-of-flight mass spectroscopy methods are employed for studying processes occurring during capture of electrons by 3He2+ and Ar6+ multiply charged ions with energy 6z keV (z is the ion charge) from C2H n molecules (n = 2, 4, 6) with different multiplicities of C-C bonds. Fragmentation schemes of the molecular ions formed in such processes are established from analysis of correlations of recording times for all fragment ions. The absolute values of the cross sections of capture of an electron and capture with ionization are measured, as well as the cross sections of formation of fragment ions in these processes. The absolute values of total capture cross sections for several electrons are determined.

the field of atomic physics, one of the creators of the modern theory of atomic collisions, Honored Scientist of Russia, Professor Emeritus at St. Petersburg University, died on 15 November 2010. Yu N Demkov was born on 12 April 1926 in Leningrad into the family of engineer-architects designing many public buildings in Leningrad and other cities in the USSR. He graduated magna cum laude from high school in 1942 in the city of Yaroslavl' during the evacuation and entered the Moscow Institute of Steel in 1943. In 1944, when he was 18 years old, Y N Demkov was drafted into the acting army and served as a soldier in the First Ukrainian Front during World War II. In September 1945 he was demobilized, went back to Leningrad, and joined the sophomore class of the Department of Physics at Leningrad State University, where he worked all his life. After graduating with summa cum laude from Leningrad State University in 1949, YuNDemkov joined as an assistant the Chair of Theoretical Physics headed at that time by Academician V A Fock. His graduation thesis, ``Charge exchange in atomic collisions'', proved to be quite relevant and determined the main direction of his research for many years. Yurii Nikolaevich's PhD thesis was devoted to the variation principles in collision theory, which were closely related to the investigations of V A Fock. He defended a PhD thesis in 1954 and later wrote amonograph on the same topic, which was then translated into English and received a university prize in 1962. Yu N Demkov defended his doctoral dissertation, ``Slow collisions of atoms and molecules'', in 1967 and became a full professor in 1970. Yurii Nikolaevich worked successively as an assistant, senior researcher, associate professor, head of the laboratory of the theory of atomic collisions, and professor. From 1975 to 1991, he was the head of the Chair of QuantumMechanics. The work of Yu N Demkov on the collision theory of atoms and ions brought him scientific authority in theoretical physics in our country and later worldwide prominence. He obtained pioneering results in the theories of charge exchange, electron detachment, and other processes. The concepts of the `Demkov model' and `Demkov coupling' are well known in modern atomic physics. The second set of results obtained by Yu N Demkov concerns the problems of symmetry in atomic physics, in particular, when applied to the Fock symmetry of the hydrogen atom and harmonic oscillator. The most important among these results was the explanation of the internal symmetry of the Mendeleev Periodic Table and the so-called (n‡ l, n) energy-level occupation rule. Here, he managed to combine in whole the work of Maxwell on the so-called `fish eye', of Mendeleev, Bohr, and Fock on the hydrogen atom symmetry. Yurii Nikolaevich also obtained, together with G F Drukarev and V N Ostrovskii, fundamental results in the development of the method of zero-radius potentials in atomic physics. The results of these studies are presented in the monograph Method of Zero-Radius Potentials by Yu N Demkov and V N Ostrovskii [(Leningrad: Leningrad State University, 1975), which was translated into English (Plenum Press, 1988)] and awarded a University First-Class Prize. Yu N Demkov's significant achievement was the discovery of a new class of problems in collision theory, so-called harmonic scattering, and the development (together with I V Komarov, A P Shcherbakov, and D I Abramov) of the original theory of this scattering using conformal mappings. This work was awarded an Academician V A Fock Prize of the Russian Academy of Sciences. Other work of Demkov includes original and unexpected results obtained in neutrino focusing studies; polynomial solutions of the problem of the Uspekhi Fizicheskikh Nauk 181 (5) 565 ± 566 (2011) DOI: 10.3367/UFNr.0181.201105l.0565 Translated by M N Sapozhnikov PERSONALIA PACS number: 01.60.+q

Luminescent and structural properties of n -FZ-Si and n -Cz-Si implanted with Si ions at amorphizing doses and annealed at 1100°C in a chlorine-containing atmosphere have been studied. An analysis of proton Rutherford backscattering spectra of implanted samples demonstrated that an amorphous layer is formed, and its position and thickness depend on the implantation dose. An X-ray diffraction analysis revealed that defects of the interstitial type are formed in the samples upon annealing. Photoluminescence spectra measured at 78 K and low excitation levels are dominated by the dislocation-related line D1, which is also observed at 300 K. The peak position of this line, its full width at half-maximum, and intensity depend on the conduction type of Si and implantation dose. As the luminescence excitation power is raised, a continuous band appears in the spectrum. A model is suggested that explains the fundamental aspects of the behavior of the photoluminescence spectra in relation to the experimental conditions.