Surface composition modification of tungsten higher oxide under He<Superscript>+</Superscript> ion bombardment

The surface reduction of higher oxide WO₃ under irradiation by He⁺ ions with the energies 1 and 3 keV in a high vacuum is investigated by X-ray photoelectron spectroscopy. It is found that lower WO₂ and intermediate WO _x (2 < x < 3) oxides form first in WO₃ surface layers under He⁺ ion bombardment, and with an increase in the irradiation dose metallic tungsten forms. It is shown that the degree of irradiated oxide surface metallization increases with an increase in the energy of the bombarding He⁺ ions. A comparison of WO₃ oxide surface composition modification under He⁺ and Ar⁺ ion irradiation is presented.     

Composition and properties of nanoscale Si structures formed on the CoSi<Subscript>2</Subscript>/Si(111) surface by Ar<Superscript>+</Superscript> ion bombardment

The variations in the composition and structure of CoSi₂/Si(111) surface layers under Ar⁺ ion bombardment with subsequent annealing has been studied. It has been demonstrated that nanocluster phases enriched with Si atoms form on the CoSi₂ surface at low doses D ≤ 10¹⁵ cm^–2, and a pure Si nanofilm forms at high doses.     

Inelastic energy losses in single and double collisions of keV-energy Ar<Superscript>+</Superscript> ions with Be,C, Al,Si, Ge,and in targets

Inelastic energy losses Q in scattering of Ar⁺ ions with an initial energy of E ₀ = 5 keV from Be, C, Al, Si, Ge, and In targets are determined using low-energy ion scattering spectroscopy. In spite of the fact that Ar⁺ ion beams are used in the overwhelming majority of applied studies devoted to analysis of the elemental composition and structure of materials for modern electronics, information on inelastic losses for these bombarding particles is scarce. It is shown that the knowledge of the value of Q makes it possible to correctly interpret the energy spectra of particles emitted during ion bombardment of the surface.     

Composition,morphology, and electronic structure of the nanophases created on the SiO<Subscript>2</Subscript> Surface by Ar<Superscript>+</Superscript> ion bombardment

The influence of Ar⁺ bombardment on the composition and the structure of the SiO₂/Si surface is studied. A thin Si film is found to form on the SiO₂ surface subjected to high-dose ion bombardment.     

Kinetics of radiation-induced segregation in 12Cr-MoWSiVNbB steel after Ni<Superscript>++</Superscript> and He<Superscript>+</Superscript> ion irradiation

Ferritic-martensitic 12Cr-MoWSiVNbB (EP-823) steel was irradiated with 7 MeV Ni⁺⁺ ions within fluence interval 5 × 10¹⁸−5.4 × 10¹⁹ ions/m² and with 30 and 70 keV He⁺ ions within fluence interval 10²⁰–10²¹ ions/m² at 500°C. Results from a comparative analysis of Cr and Si radiation-induced segregation profiles near the surface are presented. Dependence of the amount of surface segregation on damage dose, displacement generation rate, and radiation-induced point defects concentration is established.     

Interaction of <Superscript>3</Superscript>He<Superscript>2+</Superscript> and Ar<Superscript>6+</Superscript> ions with acetylene,ethylene, and ethane molecules

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.     

Polymerization of solid C<Subscript>60</Subscript> under C<Stack><Subscript>60</Subscript><Superscript>+</Superscript></Stack> cluster ion bombardment

The structure transformation occurring in fullerene film under bombardment by 50 keV C₆₀⁺ cluster ions is reported. The Raman spectra of the irradiated C₆₀ films reveal a new peak rising at 1458 cm⁻¹ with an increase in the ion fluence. This feature of the Raman spectra suggests linear polymerization of solid C₆₀ induced by the cluster ion impacts. The aligned C₆₀ polymeric chains composing about 5–10 fullerene molecules have been distinguished on the film surface after the high-fluence irradiation using atomic force microscopy (AFM). The surface profiling analysis of the irradiated films has revealed pronounced sputtering during the treatment. The obtained results indicate that the C₆₀ polymerization occurs in a deep layer situated more than 40 nm below the film surface. The deep location of the C₆₀ polymeric phase indirectly confirms the dominant role of shock waves in the detected C₆₀ phase transformation.     

Phase transformations in CuO caused by bombardment by He<Superscript>+</Superscript> ions and by the action of spherical shock waves

The valence state of copper ions and the phase composition of copper monoxide CuO subjected to bombardment by He⁺ ions and explosive shock waves are studied by the methods of x-ray photoelectron spectroscopy (XPS) and x-ray emission spectroscopy (XES). Measurements of photoelectron Cu 2p and emission O K_α spectra revealed a decrease in the concentration of Cu²⁺ ions and partial reduction of CuO to Cu₂O as a result of both ion bombardment and shock-wave loading. The concentration of the Cu₂O phase attained values of 10–15%. The Cu₂O phase is revealed by the XPS and XES methods even at concentrations lower than its threshold concentration for detection by x-ray diffraction measurements. This points to the effectiveness of XPS and XES techniques in studying nanocrystalline materials and defect structures containing finely dispersed inclusions. A model for the emergence of Cu₂O due to the formation of charged clusters under the action of stress waves is proposed.     

Micro-Raman spectroscopic investigation of NiSi films formed on BF<Subscript>2</Subscript><Superscript>+</Superscript>-, B<Superscript>+</Superscript>- and non-implanted (100)Si substrates

The micro-Raman spectroscopic technique was used to investigate vibrational properties of NiSi thin films formed on three different (100)Si substrates: non-implanted, 20 keV BF₂⁺-implanted, and 20 keV B⁺-implanted. Raman measurements were also performed on NiSi powder to identify various phonon modes associated with different selection rules of group theory. It was found that the Raman peaks for NiSi thin films formed on the BF₂⁺-implanted substrate were broader and shifted to lower frequencies compared to those for films formed on the other substrates. The broadening of the Raman peaks for these films, which also exhibit much improved thermal stability, is attributed to the small grains that probably result from the segregation of fluorine to grain boundaries and interfaces. It is further proposed that grain boundary segregation influences the stress in the silicide film, resulting in shifts in phonon peak positions. PACS 78.30.Am; 74.25.Kc; 68.35.Dv; 68.55.Ln; 66.30.Jt     

Study of interface mixing induced by Ar<Superscript>+</Superscript> ion irradiation on Ag–Ge bilayer system

A 400 keV ⁴⁰Ar⁺ ion beam was utilized to induce mixing between two thin layers of Ag and Ge. Rutherford Backscattering Spectrometry and Electrical Resistivity Measurements were employed as probes to investigate the kinetics of ion mixing. The intermixed region was studied at several fluences up to 1.7×10¹⁷ ions/cm² at a constant flux of 0.25 μA/cm². The “RUMP” simulation computer code was used to assist in the evaluation of the experimental results from the spectra. The analysis of the Rutherford Backscattering Spectrometry spectra shows that increasing the Ar⁺ fluence enhances the Ag–Ge intermixing. To describe the mixing process, mixing rate parameters were calculated and compared with the theoretical models’ predictions. Børgesen’s local thermal spike model was found to accurately predict the diffusion in the Ag–Ge interface. An increase in the electrical resistivity of the film was detected during irradiation.     

Distribution of <Superscript>28</Superscript>Si, <Superscript>29</Superscript>Si,and <Superscript>30</Superscript>Si isotopes under plastic deformation in subsurface layers of Si: B crystals

The redistribution of ²⁸Si, ²⁹Si, and ³⁰Si isotopes in subsurface layers of Si: B single crystals after their plastic deformation has been revealed. It has been found that the distribution profile of ²⁸Si and ²⁹Si isotopes becomes smoother after deformation, whereas the ³⁰Si isotope distribution remains unchanged. A change in the subsurface profile of the ²⁹SiO oxide is observed, which indicates the migration of the ²⁹Si isotope in the composition of oxygen complexes during plastic deformation.     

Multiple particle break-up study of low excited states in <Superscript>9</Superscript>Be: The ghost peak in the <Superscript>8</Superscript>Be excitation energy spectrum visited

The aim of this work is to find out the origin of the anomalous resonance in ⁸Be seen in the reactions through excited states in ⁹Be. We have populated the ⁹Be excited states by β-decay of ⁹Li. Energy and direction of the two α particles has been detected and the neutron spectra reconstructed. In our work we identified the “anomalous resonance" in ⁸Be observed in several reaction studies as coming from the decay of the 2.43 and 2.78 MeV states in ⁹Be. This anomalous resonance appears when the two detected α particles are assumed to form a resonance in ⁸Be. We argued that the main decaying channels for these two levels in ⁹Be do not involve ⁸Be.     

<Superscript>29</Superscript>Si, <Superscript>27</Superscript>Al, <Superscript>1</Superscript>H and <Superscript>23</Superscript>Na MAS NMR Study of the Bonding Character in Aluminosilicate Inorganic Polymers

²⁹Si, ²⁷Al, ¹H and ²³Na solid-state magic-angle spinning (MAS) nuclear magnetic resonance (NMR) has been used to relate nominal composition, bonding character and compressive strength properties in aluminosilicate inorganic polymers (AIPs). The ²⁹Si chemical shift varies systematically with Si-to-Al ratio, indicating that the immediate structural environment of Si is altering with nominal composition. Fast ¹H MAS and ²⁹Si T _SiH/T _1ρ relaxation measurements demonstrated that occluded pore H₂O mobility within the disordered cavities is slow in comparison with H₂O mobility characteristics observed within the ordered channel structures of zeolites. The ²⁷Al MAS NMR data show that the Al coordination remains predominantly 4-coordinate. In comparison with the ²⁹Si MAS data, the corresponding ²⁷Al MAS line shapes are relatively narrow, suggesting that the AlO₄ tetrahedral geometry is largely unperturbed and the dominant source of structural disorder is propagated by large distributions of Si–O bond angles and bond lengths. Corresponding ²³Na MAS and multiple-quantum MAS NMR data indicate that Na speciation is dominated by distributions of hydration states; however, more highly resolved ²³Na resonances observed in some preparations supported the existence of short-range order. New structural elements are proposed to account for the existence of these Na resonances and an improved model for the structure of AIPs has also been proposed. Authors' address: John V. Hanna, NMR Facility, Institute of Materials and Engineering Science, Lucas Heights Research Laboratories, Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW 2234, Australia     

Piezoelectric coefficients of multilayer Pb(Zr,Ti)O<Subscript>3</Subscript> thin films

Sol–gel techniques were used to prepare thin films of Pb(Zr _x ,Ti_1−x )O₃ (PZT) with three different Zr/Ti ratios and a graded PZT film with three different compositional layers. A Michelson interferometer was used to measure the thickness strains due to an applied ac electric field. Effective d ₃₃ piezoelectric strain coefficients were computed from the experimental data. Interfacial pinning caused these coefficients to differ from the true ones. They were corrected for the pinning using both an analytical model and finite-element analysis. The corrected coefficients of the PZT (52/48) sample were in excellent agreement with values of bulk materials. The coefficients of the multilayer sample were very low, probably due to insufficient poling or domain switching.     

Studies on the analytical potential energy function of diatomic molecular ion XY<Superscript>+</Superscript> using variational method

A new analytical potential energy function for diatomic molecular ion XY⁺ is proposed based on the energy consistent method (ECM). The Coulomb potential included in the new ionic potential contains multipole corrections, converges quickly and is variationally, changeable. The new potential and the ECM are applied to variationally studying the potential energies of eight electronic states of several diatomic molecular ions: the A²π state of CO⁺, the X²∑_g⁺ state of Li₂⁺, the X²∑_g⁺ state of He₂⁺, the 1²∏_u state of Na₂⁺, the A²∏_u state of N₂⁺, the X¹∑⁺ state of KrH⁺, the X²∑⁺ state of SiO⁺ and the A²π state of SO⁺ ion. The present results agree excellently with the experiment-based Rydberg-Klein-Rees (RKR) potentials, and are superior to the commonly used Huxley-Murrell-Sorbie (HMS) analytical potentials, and are better in some cases than some quantum mechanicalab initio potentials in the ionic asymptotic and dissociation regions.     

Secondary ion emission from a GaAs single crystal upon bombardment with Bi<Stack> <Subscript> <Emphasis Type="Italic">m</Emphasis> </Subscript> <Superscript>+</Superscript> </Stack> cluster ions

Secondary-ion mass spectra and energy distributions upon bombarding a gallium arsenide single crystal using Bi_m⁺(m = 1–5) cluster ions with energies of 2–12 keV are investigated. The gallium cluster ion yield grew nonadditively with the number of atoms in the cluster projectiles. A quasi-thermal component found in the energy spectra of secondary Ga⁺ and Ga₂⁺ ions is indicative of the occurrence of the thermal spike mode upon cluster ion bombardment. The quasi-thermal component in the yield of atomic Ga⁺ ions upon bombardment with Bi₂⁺–Bi₅⁺–ions is 35–75%.     

Study of the formation and unimolecular fragmentation of Si<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>O<Stack><Subscript><Emphasis Type="Italic">m</Emphasis></Subscript><Superscript>+</Superscript></Stack> clusters under ion bombardment

The dependences of the emission and fragmentation of clusters sputtered by Xe⁺ ions from the surface of Si _n O _m ⁺ on the oxygen pressure near the bombarded surface are studied using secondary ion mass spectrometry. It is shown that the process of Si _n O _m ⁺ cluster formation under ion bombardment can be described within the framework of the mechanism of combinatorial synthesis by taking into account the mutual reversibility of the reactions of formation and unimolecular decay.