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A photovoltaic effect was observed under exposure to 810-nm laser light on the atomically clean surface of an n-GaAs wafer etched with Ar+ ions: open-circuit voltage in current–voltage (J–V) light characteristics was as high as 47 mV. The effect is due to the formation of a p–n structure under Ar+ ion bombardment in the near-surface bulk layer (~ 7 nm thick) via the conversion of the conductivity type of the near-surface layer from n to p. The effect of the conductivity type conversion under pure mechanical ion action manifested itself in that the Fermi level approached the valence band top, which was detected by high-resolution photoelectron spectroscopy with the use of a synchrotron radiation. The formation of the p–n junction in the structure was confirmed by dark J–V characteristics, which show a diode effect at voltages in the range (0–0.6) eV with a direct-to-reverse current ratio as large as 103. The results obtained show that the near-surface bulk properties of n-GaAs treated by the most widely employed surface cleaning procedure via etching with a beam of Ar+ ions differ dramatically from the pristine deep bulk.

The excitation spectrum of GaAs has been studied by reflection electron energy loss spectroscopy. In addition to dominant collective excitations, a series of single-electron transitions of a core Ga 3d electron to previously unknown unoccupied states located above the Fermi level by 1.25, 3.7, and 6.8 eV have been detected in the spectrum. It has been shown that the detected states appear near the ion core of Ga because of an increase in its effective charge at excitation. Since the detected electronic levels are equidistant, they can be described by a subnanometer spherical quantum dot model. It has been shown that one of the decay channels of the detected states involves the emission of ultraviolet radiation.

The core-level and valence band electronic structure of the n-GaAs (100) has been studied by synchrotron-based high-resolution photoelectron spectroscopy after irradiation by an Ar+ ion beam with energy Ei = 1500 eV and fluence Q = 1 × 1015 ions/cm2. Conversion of the conductivity type of the surface layer and formation of a p–n structure have been observed. The p-surface layer thickness (d ~ 5.0 nm) and band structure were experimentally determined from the Ga3d photoelectron spectrum by separation and analysis of the low intense n-type bulk contribution from deeper layers. A band diagram of the p–n junction formed on the n-GaAs surface by Ar+ ion bombardment was reconstructed. The p–n junction proved to be unexpectedly narrow compared to the extended tail of the implanted ion depth distribution.

A highly defective ~10-nm-thick layer was fabricated in a high vacuum by 2.5 keV Ar+ ion bombardment of the n-GaAs surface. Valence band photoelectron spectra showed a p-type conductivity of the layer arising due to the high concentration of mechanically created point defects (p-centers). J–V characteristics measured ex situ for the structure consisting of the irradiated p-layer on the n-type substrate revealed a diode effect. Analysis of the data attributes the effect to the formation of a specific p–n junction. Thereby, we demonstrated that Ar+ ion bombardment of the n-GaAs surface results in that a nanostructure with the p–n junction properties is formed. The p–n junction under consideration seems to deserve further study and possible application since it can be formed in high-vacuum clean conditions directly by exposure to a low-energy Ar+ ion beam without wet lithography.

Oxidation specific of the defected GaAs has been considered on the basis of elemental and chemical composition study of the oxide layer naturally emerged on the GaAs surface strongly irradiated by Ar+ ions with energy Ei = 3000 eV and fluence Q ~ 3 × 1015 cm–2. The diffusivity of elemental arsenic known to form an interface layer was shown to increase at room temperature by more than 35 orders of magnitude due to radiation defects and to amount to the value D ~ 1 × 10–17 cm2/s. Efficient room temperature diffusion results in total removal of elemental arsenic from oxide into the bulk, thus curing the damaged substrate.

The concentration profiles of defects produced in structures upon the implantation of nitrogen ions into GaAs epitaxial layers with an uncovered surface and that covered with an AlN film and subsequent annealing are studied. The ion energies and the implantation doses are chosen so that the nitrogen-atom concentration profiles coincided in structures of both types. Rutherford proton backscattering spectra are measured in the random and channeling modes, and the concentration profiles of point defects formed are calculated for the samples under study. It is found that the implantation of nitrogen ions introduces nearly the same number of point defects into structures of both types, and the formation of an AlN film by ion-plasma sputtering is accompanied by the formation of an additional number of defects. However, the annealing of structures of both types leads to nearly the same concentrations of residual defects.

An approach to solving the problem of the in situ bandgap determination in the extremely thin and chemically active nitride nanolayers fabricated in high vacuum on the n-GaAs surface has been suggested. The approach is based on measuring the interband transitions involving the quantum well states by the method of electron energy loss spectroscopy. The bandgap of the nitride layer formed on the GaAs surface by low-energy $${\text{N}}_{2}^{ + }$$ ion implantation was determined to be 0.2 eV less than that of GaAs, which evidenced for creation of the GaAsN dilute alloy on the GaAs surface.

The elemental and chemical compositions throughout the thickness of the GaAs native oxide layer slightly irradiated by Ar+ ions have been studied by synchrotron-based photoelectron spectroscopy at different photon energies enabling variation of probing depth. The presence of only two phases was observed: of the gallium oxide Ga2O3 and elementary arsenic Aso generated due to complete decay of arsenic oxides under the ion irradiation. Depth composition profiles were determined nondestructively. Despite inhomogeneous depth distribution, these profiles demonstrated domination (90 at %) of the dielectric Ga2O3 phase virtually throughout all the oxide thickness (~2 nm).

The electronic structure and chemical composition of the n-GaAs surface after implantation of N2+ ions with energy Ei = 3000 eV and fluence Q ∼ 3 × 1015 cm-2 were studied by synchrotron-based X-ray photoelectron spectroscopy to clarify effects of low-energy nitrogen ion implantation on A3B5 semiconductor surfaces. Conversion of the conductivity type and creation of a p-n structure on the n-GaAs surface were revealed under N2+ ion irradiation. The conductivity type transformation was shown to occur due to pure mechanical action of nitrogen ions, resulting in formation of Ga anti-site acceptors. The ∼ 10 nm-thick p-layer obtained consisted of concentrated GaAs1-xNx (x ∼ 0.1) alloy whose bandgap width is known to be essentially narrower compared to the pristine GaAs semiconductor. Therefore, the structure formed is a nano-heterosctructure incorporating the semiconductor alloy whose properties are considered to be attractive for infrared applications. The obtained GaAsN electron binding energies (EB (N1s) = 397.0 eV, EB (Ga3d) = 19.42 eV and EB (As3d) = 41.25 eV) can be used for identification of the GaAsN alloy phase. An approach to 3D p-n structures formation was suggested using nitrogen ion beam without wet lithography.

Poor dielectric properties of GaAs oxides are the drawback of the GaAs-based electronics preventing using these oxides as dielectric layers. The elemental and chemical compositions of the GaAs native oxide layer slightly irradiated by Ar+ ions with the fluence Q ~1 ∗ 1014 ions/cm2 have been studied by the synchrotron-based photoelectron spectroscopy. The effect of selective and total decay of arsenic oxides followed by diffusive escape of arsenic atoms from the oxide layer has been revealed. The effect results in three-fold Ga enrichment of the upper layer of the native oxide and in strong domination (~90 at%) of the Ga2O3 phase which is known to be a quite good dielectric with the bandgap width as wide as 4.8 eV. A band diagram was obtained for the native oxide nanolayer on the n-GaAs wafer. It has been shown that this natural nanostructure has a character of a p-n heterojunction.

The density of states of the valence band of a p-GaAs layer formed on an n-GaAs surface owing to the bombardment by 2500-eV Ar+ ions has been studied by photoelectron spectroscopy. A number of peaks have been detected in the spectrum of the edge of the valence band in the binding energy range EV < 1.2eV. Their number and energy positions correspond to the quantum confinement levels calculated for a hole quantum well on the surface with the width about the ion penetration depth Rp = 3.6nm. Electronic transitions from these levels to the bottom of the conduction band have been revealed in the spectrum of characteristic energy losses of electrons reflected from the surface. Thus, it has been shown that the action of the argon ion beam on n-GaAs results in the formation of a quantum well on the surface.

Secondary-ion mass spectrometry and Rutherford proton backscattering have been used to measure the concentration profiles of nitrogen atoms and examine the defect structure of epitaxial GaAs layers implanted with 250-keV N+ ions at doses of 5 × 1014–5 × 1016 cm–2. It was found that no amorphization of the layers being implanted occurs at doses exceeding the calculated amorphization threshold, a concentration of point defects that is formed is substantially lower than the calculated value, and a characteristic specific feature of the defect concentration profiles is the high defect concentration in the surface layer.

Electronic structure and chemical composition of GaAs-based semiconductors are considered to be well characterized by photoelectron spectroscopy and other surface-sensitive methods. However, effect of ion irradiation on electron binding energies and band structure of semiconductors can drastically distort results of diagnostics. This effect was studied by synchrotron-based XPS applied to n-GaAs wafer after 1250 eV - Ar+ ion exposure with fluence Q ~ 1 × 1015 ions/cm2 which is typical for preparation of atomically clean surfaces. Mechanical action of ions was shown to change the n-GaAs electron binding energies by the value of the bandgap width due to creation of defect states, and conversion of the conductivity type from n to p. The Ga3d and As3d core-level binding energies for p-GaAs and n-GaAs were measured in one experiment on the p-n plane structure formed due to irradiation: EB(p/n) = 19.3/20.4 eV and EB(p/n) = 41.3/42.4 eV. The p-layer nanothickness was determined and the band diagram of the p-n GaAs structure was constructed. The revealed effect may be comparable with core-level chemical shifts and should be taken into account to avoid mistakes in the XPS chemical composition diagnostic of GaAs-based semiconductors.

Auger-electron spectroscopy has been used to study in situ the initial stage of graphite oxide (GO) reduction under the action of a low-intensity electron beam that does not lead to heating of the irradiated region. It was found that this stage evolves at a rate that is tens of times the rate of the subsequent reduction. It was shown that the fast stage is associated with the removal of oxygen groups from the GO surface. The effective cross sections of the initial and subsequent stages of GO reduction by 1500 eV electrons were found to be σin ~ 0.5 × 10–16 cm2 and σav ~ 1.2 × 10–18 cm2, respectively.

The thickness, elemental and chemical compositions of the native oxide naturally formed on a perfect GaAs(1 0 0) crystal grown by MBE have been studied by Auger electron spectroscopy (AES) and electron energy-loss spectroscopy (EELS) to specify the oxidation mechanism and to confirm or reject the questionable presence of elemental arsenic in the natural oxide. Elemental arsenic (Aso) arising in the oxidation process due to reduction of As2O3 by the GaAs substrate was revealed at the Auger energy of 1225.8 eV and shown to reach ~16 at% of the oxide whose thickness was determined to be ~4 nm. Aso was shown by EELS to form a segregate with the plasmon energy of 18.1 eV. Room temperature oxygen diffusivity through the finally formed oxide layer was estimated to be low enough (D

A change in the elemental composition of a graphite oxide film irradiated by a weak electron beam, which does not heat the irradiated region, has been studied by Auger electron spectroscopy. The process of nonthermal electron-stimulated reduction of graphite oxide, which occurs because of the excitation of the electronic system of the material, has been detected.

Graphite oxide (GO) nanofilms on the SiO 2 /Si surface have been studied by photoelectron spectroscopy (XPS) with synchrotron radiation and by Auger electron spectroscopy (AES). Auger electron energies were determined for the basic functional GO groups: hydroxyl (C OH) and epoxide (C O C). The data obtained enabled developing a technique for the GO chemical and elemental composition determination. The technique allows controlling the hydrogen content in GO despite the impossibility of Auger emission from hydrogen.

A nitride nanolayer fabricated on a GaAs (100) surface by implanting ions N2+ (Ei = 1.5 keV) has been studied by high-resolution photoelectron spectroscopy with the use of synchrotron radiation. It has been found that, apart from the dominant GaN wide-gap semiconductor phase, an additional phase of the GaAs1 − xNx narrow-gap solid solution (x < 0.10) is present in the nitride layer. It has been shown that the nitride layer created by ion implantation is a nanostructure with an attribute of a system of quantum dots, since it consists of nanoclusters of the narrow-gap semiconductor in the wide-gap matrix.

Monte Carlo simulation of the C60-fullerite film irradiation by 5 keV electron beam at normal incidence has been performed. Average transverse coordinates of the primary and secondary electrons as well as the density of collisions of several types were drawn in dependence on the penetration depth. It was shown that a swarm of low energy secondary electrons provides efficient excitation of valence electrons and gives the main contribution to polymerization of C60-fullerite.

Effective cross-sections σD(E) of fullerite C60 modification by electrons in the energy range E = 0.25–3000 eV were obtained using electron energy loss spectroscopy. Comparison of σD(E) with cross-section σF(E), describing fragmentation of individual fullerenes C60 in the gas state and known from literature, revealed several orders of magnitude difference between the absolute values of these cross-sections and the inverse behavior of their energy dependencies. This fact evidences that the mechanism of electron-induced destruction of fullerite C60 drastically differs from the one implied by the model of successive fragmentation of separate fullerenes and that condensed fullerenes C60 are radically more stable than it was considered earlier.

Transformation of the chemical composition and electron structure of graphite oxide (GO) nanolayers as a result of their annealing in hydrogen has been studied by X-ray photoelectron spectroscopy using synchrotron radiation. It is established that both the chemical composition and bandgap width of GO can be controlled by varying the temperature and duration of heat treatment. By this means, the properties of GO nanolayers can be smoothly changed from dielectric to semiconductor.

The composition of a nitride nanolayer formed on a GaAs(100) surface by the implantation of ions with an energy of Ei = 2.5 keV and the chemical state of nitrogen in this layer have been studied by the method of Auger electron spectroscopy. It is established that, in addition to GaN, a GaAsN solid solution phase is formed in the ion-implanted layer. The energies of N KVV Auger electron transitions in these phases are determined as EA(GaN) = 379.8 ± 0.2 eV and EA(GaAsN) = 382.8 ± 0.2 eV (relative to the Fermi level), which allowed the distribution of nitrogen between these phases to be evaluated as [N(GaN)] = 70% and [N(GaAsN)] = 30%. It is established that an argon ion beam produces a chemical effect on the nitride layer, which is related to a cascade mixing of the material. Under the action of the argon ion bombardment, the distribution of nitrogen in the indicated phases changes to opposite. As a result a nitride nanolayer is formed in which the narrow-bandgap semiconductor (GaAsN) predominates rather than the wide-bandgap component (GaN).

Large-scale graphene fabrication by thermal and chemical reductions of graphene oxide has faced the problem of defect formation. To solve the problem, we have considered a physically alternative reduction process including electronic excitation followed by the oxygen group detachment from the carbon sheet without capturing a sheet of carbon atoms. Single-layer graphene oxide films were studied by photoemission spectroscopy in the course of monochromatic synchrotron X-ray radiation with in situ control of the layer thickness, chemical composition, atomic ordering, and defect concentration exactly in the modified area. The radiation flux was too low to heat the film. A non-thermal and low-destructive effect of X-ray induced graphene oxide reduction has been revealed. Transformation of the sp3 σ bonds into sp2 π ordered bonds, bandgap closing, and significant diminishing of the oxygen content (below 5 at. %) have been observed without any signs of defects in the photoemission spectra. The effective cross sec...

An extremely high rate of destruction of fluorinated fullerite С60F18 by accelerated electrons was revealed. This rate was three orders of magnitude higher than that of the ordinary fullerite C60. High rate of the modification was assumed to be caused by the efficient mechanism of fragmentation of С60F18 molecule compared to the mechanism of polymerization of fullerite C60. The conclusion has been made that films of fluorinated fullerites are perspective as an electron-beam resist for dry nanolithography.

The electronic structure of the well-defined n -GaAs (100) near-surface layer irradiated by an ion beam of the keV energy range has been studied by synchrotron-based photoelectron spectroscopy. Conversion of the conductivity type from n into p has been revealed in the irradiated layer several nm thick, thus resulting in the junction formation. The effect manifests itself in adjoining the valence band edge to the Fermi level. Transformation of the conductivity type has been shown to be caused by Ga-antisite point defects generated by mechanical impact of inert argon atoms diffusing away after implantation. The possibility of local formation of a nanojunction by ion beam within the beam spot has been demonstrated.

AbstractDetailed information on GaAs oxide properties is important for solving the problem of passivating and dielectric layers in the GaAs-based electronics. The elemental and chemical compositions of the native oxide layer grown on the atomically clean surface of an n -GaAs (100) wafer etched by Ar^+ ions have been studied by synchrotron-based photoelectron spectroscopy. It has been revealed that the oxide layer is essentially enriched in the Ga_2O_3 phase which is known to be a quite good dielectric as compared to As_2O_3. The gallium to arsenic ratio reaches the value as high as [Ga]/[As] = 1.5 in the course of oxidation. The Ga-enrichment occurs supposedly due to diffusion away of As released in preferential oxidation of Ga atoms. A band diagram was constructed for the native oxide nanolayer on the n -GaAs wafer. It has been shown that this natural nanostructure has features of a p–n heterojunction.

The structure of C1s and F1s core electron levels in C60F18 and C60F36 fluorinated fullerenes has been studied by X-ray photoelectron spectroscopy using synchrotron radiation. It is established that C1s levels of carbon atoms not bound to fluorine in these compounds are shifted down by 1.0 and 1.6 eV relative to the C1s level in the usual C60 fullerene, so that the binding energies of the core electron levels in C60F18 and C60F36 amount to Eb (C1s, C-C) = 285.7 and 286.3 eV, respectively. These values are characteristic and can be used for the identification of both homogeneous fluorinated fullerenes and combined materials comprising a mixture of various fluorinated fullerenes with each other and with different carbon-containing based materials.

Photoemission spectra of solid fluorinated fullerenes C60Fx (x = 18, 36) were measured in comparison with parent C60 using synchrotron radiation (hν = 120 eV) providing the spectra in the density of states mode. Creation of the ion-like bonding of fluorine and disappearance of the π-states were observed to be a result of fluorination. Disappearance of the upper lying π-states was revealed to be a reason of the band gap widening upon fluorination.

Formation of a lithographic image (a pixel) of electron nano‐probe has been studied using fullerite C60 film as a negative electron beam resist. A mechanism of widening a pixel due to modification of the resist by secondary electrons has been revealed. Widening a pixel occurs due to diffusion of secondary electrons around the area filled by primary and scattered electrons. The mechanism manifests itself in formation of a large carbon cluster‐pixel on which small cluster‐pixel formed by primary electrons is superimposed. It was shown that the role of the revealed mechanism may be important in the case of formation of lithographic pictures and carbon nanostructures with high density of elements.

Comparative study of near edge X‐ray absorption fine structure spectra (NEXAFS) of fluorinated fullerenes C60Fx (x = 0, 18, 36) has been implemented. Local density of unoccupied states was obtained and an accurate boundary between π* and (π+σ)* states was determined. The experimental evidence was found that unoccupied π*‐ states of C60Fx are delocalized ones and form cluster shells that sequentially disappear in fluorination starting from the highest state. As a result, the density of the lowest π* ‐ state (LUMO) was revealed to remain being constant in fluorination despite the π ‐electron subsystem exhaustion.

Energy transfer in collision of light atom(ion) with a single‐walled carbon nanotube (SWCNT) were investigated theoretically within two approximations, frozen electron subsystem and adiabatic motion, which correspond to high and low energi limits, respectively. Average energy losses as well as standard deviations were obtained as functions of the collision energy and ion charge for E = 0.1 ÷ 5 keV and Q = 0 ÷ 4. It is demonstrated that contribution to energy losses by elastic scattering dominates in all considered energy range and light ion can transfer energy to SWCNT of the order of tens eV which is enough for CNT destructions.

We have observed the energy structure in the density of occupied states of graphene grown on n-type 6H-SiC (0001). The structure revealed with photoelectron spectroscopy is described by creation of the quantum well states whose number and the energy position (E1 = 0.3 eV, E2 = 1.2 eV, E3 = 2.6 eV ) coincide with the calculated ones for deep (V = 2.9 eV) and narrow (d = 2.15 A) quantum well formed by potential relief of the valence bands in the structure graphene/n-SiC. We believe that the quantum well states should be formed also in graphene on dielectric and in suspended graphene., Comment: 7 pages, 4 figures

The electronic structure of the solid polycrystalline fluorinated fullerene C60F18 has been investigated by reflection electron‐energy‐loss spectroscopy for the first time. The elementary excitation spectrum of the solid C60F18 was compared with the respective spectrum of the solid C60, and an explanation of their significant similarity in the range of π→π∗ transitions was suggested.

Simulating of fullerite C60 polymerization under the electron beam irradiation was performed within the framework of proposed model. The number of arising covalent bonds was assumed to be proportional to the number of excited and ionized C60 molecules. The polarization, exchange, and muffin‐tin size were taken into account in simulating elastic scattering events; inelastic ones were modeled within the frame of dielectric formalism for scattering on valence electrons and as a binary collisions for ionization of deep atom levels. It was found out that small variations in the momentum‐ and frequency‐dependent loss function may considerably affect both the evolution of low energy secondary electrons and the character of the electron induced structure transformation.

It has been shown that low size dispersion systems of carbon nanoclusters can be fabricated by ion irradiation of fullerite C60 film through a special mask. As the mask, lavsan track membrane with more or less equal pinholes of diameter of about 60 nm was used. STM study showed that fabricated clusters have a form of the cone‐like island with average diameter of about 60 nm and height of about 5 nm.

The effect of double scattering of Ar+ ions from the surface of C, Al, Si, Ti, Ge, and In targets is studied by the method of slow scattered ion spectroscopy. Based on this effect, a technique to estimate the cluster phase of germanium atoms in the Si1−xGex solid solution with a small (5–10%) content of germanium is suggested.

A model has been suggested, and the simulation of the fullerite C60 polymerization by electrons within the energy range 0.15 ÷ 1.5 keV has been carried out. The number of created intermolecular bonds was assumed to be proportional (with a coefficient k) to the number of excited molecules. Polarization, exchange, and muffin-tin size were taken into account for elastic scattering. Ionization of deep atom levels was treated as a binary collision, and the inelastic scattering by valence electrons was described in the framework of the dielectric formalism. The comparison of results of the simulation with experimental data gave the coefficient of proportionality k∼(2 ÷ 5) · 10−3.

The photoelectron spectra of a C60 fullerene condensate are investigated. Under conditions where the photoionization (HOMO-ɛ 1) and Auger (KVV*) transitions are at resonance, the intensity of molecular lines in the photoelectron spectra increases by a factor of several tens. It is found that even insignificant destruction of the molecular structure of fullurenes under synchrotron radiation leads to quenching of the observed resonance. The quenching of the resonance manifests itself in a decrease in the intensity of the molecular lines in the photoemission spectra. The revealed effect can be used to determine the degree of radiation-induced modification of fullerenes.

The fullerite C60 modification induced by electron irradiation was studied using electron energy loss spectroscopy (EELS). We show that prolonged electron irradiation causes gradual transformation of electron and atomic structures of fullerite C60 films towards respective structures of amorphous carbon. Moreover, strongly modified parts of fullerite C60 films become thermally unevaporable. A possible mechanism of these effects is suggested. Finally, we propose a new original nanolithography technique based on two key ideas: the use of fullerite films as negative electron-beam resist and development of lithographic images by appropriate thermal treatment of these films.

Nitration of n-type GaAs (100) by N2+ ions with the energy Ei = 1.5 keV has been studied by photoelectron spectroscopy with using synchrotron radiation. Phase of GaAs1-xNx (x ∼ 0.10) alloy was revealed in the nitrated nanolayer besides GaN and nitrogen N1s core-level binding energies in GaAs1-xNx (Eb = 397.5 eV) and GaN (Eb = 396.7 eV) were measured in one experiment. It was shown that the nitrated nanolayer consists of the narrow band gap clusters of GaAs1-xNx alloy in the GaN wide band gap matrix, which can be considered as a system with quantum dots. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Photoemission spectra of valence electrons of solid C60F18 were measured in X-ray photon energy range being close to the excitation of fluorine F 1s core electron into the first unoccupied state. Enhancement of photoemission cross sections was revealed due to Auger decay of fluorine vacancy in which electron of neighboring carbon atom takes part.

The energy spectra of electrons ejected in ${\mathrm{He}}^{2+}\ensuremath{-}\mathrm{He}$ collisions were measured in the ion energy range 6--30 keV. Theoretical analysis of the ionization mechanisms has been performed on the basis of the advanced adiabatic approximation for one-electron processes and perturbation theory for two-electron processes. The ionization channel 2$p$\ensuremath{\sigma}${}^{2}$ \ensuremath{\rightarrow} 1$s$\ensuremath{\sigma}$\mathit{nd}$\ensuremath{\sigma} \ensuremath{\rightarrow} 1$s$\ensuremath{\sigma}\ensuremath{\epsilon}$d$\ensuremath{\sigma} has been revealed, which makes a considerable contribution to the ionization cross section in the keV ion energy range.

Experimental and theoretical studies of the energy spectra of electrons ejected in H{sup -}He collisions have been performed. Comparison of calculations using the Sturmian and advanced adiabatic theories with experimental data reveals the existence of a correlated electron detachment mechanism, which yields the main contribution to formation of the high-energy part of the ejected electron energy distribution. This mechanism is associated with dynamical energy transfer to the loosely bound 1s{sup '} electron of H{sup -} in the course of superpromotion of the inner 1s electron.

A new way of controlled fabrication of "metal/insulator/superconductor" (MIS) structures with nano- and subnanometer thickness of layers and interfaces is suggested. The way is based on the effect of ion-induced self-organizing restructuring of the near surface region of high temperature superconductors (HTSC). The chemical bond breaking of metal atoms with oxygen stimulated by the bombarding ions is the first stage of the effect. Then the metal atoms diffuse to the surface and form a metallic segregate in the form of a film or a cluster ensemble depending on the ion energy and irradiation dose. The irradiated region loses its superconductivity and is transformed into insulator. The thickness of the dielectric layer is determined by the penetration depth of ions which can be regulated by variation of their energy. The processes pointed out and the properties of the created structures have been studied using electron spectroscopy. As compared to the known structures, the discovered ones are characterized by qualitatively thinner layers and interfaces.