bluuebunny/crossref_metadata_2025 huggingface dataset:
Amorphization of Aubi Alloys by Laser Quenching and Ion Irradiation
Authors: Wolthuis A. , Stritzker B.
Published: March 2011

Crystalline AulO0−xBixalloy films (200≤×≤90) could be transformed into an amorphous state by either+laser (20 ns pulse length, 248 nm) or ion bombardment (Ar ions, 300 keV) of these films, which were mounted onto a substrate kept at low temperatures ( <10K). Several metastable Phases could beobtained by annealing of the amorphous phase before the starting equilibrium phase mixture was formed. The different phases were characterized by their different superconducting and electrical properties.
Effects of Pulsed Electron Beam Irradiation on Al Single Crystal With Pb Overlayers
Authors: Battaglin G. , Carnera A. , Dona L.F. , Rose Dalle , Kulkarni V.N. , Mazzoldi P. , D'Anna E. , Leggieri G. , Luches A.
Published: March 2011

The effects of pulsed electron beam irradiation (pulse width 50 ns FWHM, electron eneries from 15 to 30 keV and current density in the range of 100 to 2300 A/cm2 ) on Al-Pb systemsprepared by vacuum evaporation of Pb layers from 500 Å to 2000 Å in thickness over Al single crystals have been investigated by Rutherford backscattering (RBS) and scanning electron microscopy.

The main effects consist in a Pb loss which shows definite features as a function of the incident beam current density and in a mixing of Pb into Al which is unambiguously detected by a selective chemical etching of Pb still unreacted after irradiation.

These experimental results are discussed on the basis of some heat flow model calculations which use Monte-Carlo data for the electron depth dose function.
Reflectivity and Grazing Angle Diffraction of Polarized Neutrons
Authors: Ankner J.F. , Majkrzak C.F. , Neumann D.A. , Matheny A. , Flynn C.P.
Published: March 2011

Using polarized-neutron reflectivity, one can determine the layer-averaged magnetic structure of films and multilayers with exquisite precision. By employing the closely related phenomenon of grazing-angle diffraction, it is possible to obtain information about the in-plane structure in interfacial layers some tens of Ångstroms thick. We have used polarized-beam methods to study the Y/Gd interface using both reflectivity and grazingangle diffraction and discuss the status of these experiments.
Magnetic Domain Imaging of Epitaxial thin Films by Spin-Polarized Scanning Electron Microscopy
Authors: Allenspach R. , Stampanoni M.
Published: March 2011

The formation of magnetic domains in thin epitaxial Co/Au(111) films is investigated by spin-polarized scanning electron microscopy. Three-monolayer films are shown to decay into out-of-plane domains of micrometer size. The transition from out-of-plane to in-plane magnetization at a crossover thickness of 4.5 layers is followed by imaging the domains, and the transition is shown to occur as a continuous rotation of the magnetization. The domain size in field-free-grown perpendicular films depends linearly on film thickness. From high-resolution line scans across magnetization reversals we determine the resolution in magnetic imaging to be better than 40 nm.
Interlayer Magnetic Coupling in Transition-Metal Multilayered Structures
Authors: Levy Peter M. , Fry J.L. , Ethridge E.C.
Published: March 2011

Recent experiments have confirmed the main features of the interlayer coupling we calculated for Fe/Cr multilayers. We discuss the origins of these features and present new results on the interlayer coupling for Fe/Mo(100) multilayered structures. We find they share many of the features seen in Fe/Cr structures; in particular the rapid oscillations of the coupling which are suppressed by the roughness of the interfaces in sputtered superlattices.
Giant Magnetoresistance and Oscillatory Interlayer Exchange Coupling in Copper Based Multilayers
Authors: Parkin S.S.P.
Published: March 2011

Giant magnetoresistance values exceeding 65% at room temperature are reported in antiferromagnetically coupled Co/Cu multilayers grown on Fe buffer layers using magnetron sputter deposition. For such samples the saturation fields exceed 10 kOe. However by taking advantage of the rapid decrease of the Co interlayer magnetic exchange coupling with increasing Cu spacer layer thickness, large magnetoresistance values exceeding 35% can be obtained at room temperature for saturation fields of just a few hundred oersted.
Magnetism and Magnetoresistance of Multilayers with Two Magnetic Components. II. Au-Based Films
Authors: Okuyama T. , Dohnomae H. , Yamamoto H. , Shinjo T.
Published: March 2011

Magnetoresistance(MR) properties of Au-based multilayers including two magnetic components, i.e.\Au/Co/Au/Ni(Fe)]xn, were investigated and compared with those of Cu-based films. The interlayer coupling between Co and Ni(Fe) through Au layer was found to be strongly antiferromagnetic if the thickness is less than 35Å. Antiparallel alignment of magnetizations caused by the difference in the coercive fields of Co and Ni(Fe) layers is realized when the Au layer thickness is larger than 50Å. Then, the resistance is enhanced by the spin-dependent scattering but the observed MR ratio is smaller than the case of Cu-based multilayers.
Magnetic and Transport Properties of Ion Beam Sputtered FE/CR Multilayers
Authors: Inomata K. , Okuno S.N. , Hashimoto S. , Yusu K.
Published: March 2011

Fe/Cr/Fe sandwiches and (Fe/Cr)n, multilayers were prepared by ion beam sputtering on MgO(100) substrates by changing acceleration voltages. Lower acceleration voltage was crucial to obtain multilayers with high quality interfaces.Single crystalline Fe/Cr/Fe sandwiches were prepared with ambient substrate temperature having a relation of Fe(100)<110>//MgO(100).On the substrates with elevated temperature above 150°C,however,polycrystalline films were grown.Magnetic coupling between Fe-layers through intervening Cr layers was investigated by FMR using 9.4GHz,in which three resonance lines were observed for single crystalline Fe/Cr/Fe sandwiches and (Fe/Cr)n multilayers with antiferromagnetic Fe-layer interactions,while a single resonance line was observed for the polycrystalline films.Magnetoresistance measured on (20AFe/12ACr)5 single crystalline multilayers showed anisotropy in saturation fields Hs which are about 2 times lower in the applied field parallel to Fe<100> than to Fe,which is consistent with the magnetization process for the films.It was found that the shapes of the magnetoresistance curve vs magnetic field differ for H//Fe<100> and H//Fe<110>.
Magnetism and Magnetoresistance of Fe/Cr Composite Multilayers
Authors: Araki Satoru , Narumiya Yoshikazu , Shinjo Teruya
Published: March 2011

Fe/Cr multilayers with composite layered structures were prepared onto MgO (100) and glass substrates by alternate deposition in ultrahigh vacuum. A multilayer with two thicknesses of Fe layers shows a larger MR change, 6.2 % at RT and 13.5 % at 77 K, than a simple type ones with the applied field upto 3 k0e. This Is due to the ferrimagnetically coupled Fe layers. For the multilayers of Cr-composite type, the MR ratio could be enhanced, 12.9 % at RT with the field of 2 T.
Morphologies of Solid Surfaces Produced far from Equilibrium
Authors: Williams R. Stanley , Bruinsma Robijn , Rudnick Joseph
Published: March 2011

We present the first quantitative experimental study of the morphology of amorphous solid surfaces formed by non-equilibrium processes and compare the results with theories developed to explain the formation of such surfaces.
Thickness Dependence of the Ferromagnetism of Pd Films
Authors: Bouarab S. , Demangeat C. , Mokrani A. , Dreysse H.
Published: March 2011

We report the electronic structure of Pd(001) films with various thicknesses, within a self-consistent real-space description of the Hubbard Hamiltonian. We point out that the onset of ferromagnetism in Pd films is not a surface effect, but is directly related to the thickness of the slab: when the lattice parameter increases, films of two or three planes become ferromagnetic. Films with increasing thicknesses (from five layers to the bulk size) need a greater increase of the lattice parameter. An important supplementary lattice expansion is necessary to obtain a free-standing ferromagnetic monolayer. The surprising experimental results of Pd films on Ag or Fe substrate, are well described within this framework.
Epitaxial τMnAl/AlAs/GaAs Heterostructures with Perpendicular Magnetization
Authors: Sands T. , Harbison J.P. , Allen S.J. , Leadbeater M.L , Cheeks T.L , Brasil M.J.S.P. , Chang C.C. , Ramesh R. , Florez L.T. , Derosa F. , Keramidas V.G.
Published: March 2011

Epitaxial films of ferromagnetic τMnAl with perpendicular magnetization have been grown on {100}AlAs/GaAs substrates by molecular beam epitaxy. A multistep growth procedure involving the formation of a template followed by codeposition and subsequent annealing yields thin epitaxial τMnA1 films that exhibit the extraordinary Hall effect with nearly ideal hysteretic characteristics.
Structure and Magnetism of NI/FE Multilayers.
Authors: Jennett Nigel M. , DINGLEY D.J.
Published: March 2011

X-ray diffractometry at grazing incidence has been performed upon Nin/Fen multilayers with 6<2n<30mpl (n = no. of monolayers per nn layer, mpl), as a further test that the observed reduction in magnetisation (as n decreases) was not due to interfacial alloying. The results show that the interfaces are terraced to the extent that pinholes occur in the thinner layers. The layers became continuous for modulations 2n>10mpl. Each X-ray scan revealed a series of peaks which corresponded to integer monolayer differences in modulation periodicity. In contrast, interfacial alloying would have produced a broad single peak.

M-H loops were performed on the samples for the range of temperatures 6<T<300K using a vibrating sample magnetometer with the field always applied in the plane of the sample. The sample coercivity was observed to vary with modulation wavelength such that at a modulation of 2n=16mpl it was about a factor of three greater than at either 2n=6mpl or 2n=30mpl. The coercivity peak occurs at a value of n equal to the critical layer thickness for the transformation of the Fe from FCC to BCC. High angle X-ray diffractometry shows an apparent change in planar spacing at the same modulation layer thickness (n=8mpl).

The ratio of remnant magnetisation at low temperature to that at room temperature, RT, was greater than unity for all the samples measured. The ratio increased as the modulation period of the samples decreased. This is consistent with a modulation period dependence of the Curie temperature of the Ni/Fe multilayers.
MBE-Grown Epitaxial Co/Cr Superlattices
Authors: Vavra W. , Elagoz S. , Clarke Roy , Uher C.
Published: March 2011

A series of epitaxial Co/Cr superlattices has been grown by molecular beam epitaxy. The Cr is in a metastable hcp phase as confirmed by transmission electron microscopy, selected area diffraction, and reflection high energy electron diffraction. The Cr layers are 10Å thick in all samples while the Co layers are varied from 12Å to 40Å. The diffusion between Co and Cr is studied by SQUID magnetometry and indicates step-like interfaces in the best samples. Interfacial sharpness has also been found to be unusually sensitive to Co deposition rates, and in contrast with other superlattice systems, we find that sharper interfaces enhance parallel anisotropy. Hall effect measurements of the saturation field are within 10% of SQUID values. Magnetoresistance at 4.2K is only 1/3% which we believe is a consequence of the high density of states at the Fermi level of hcp Cr.
The Enhanced Magnetization Observed in FE/mo Multilayers Deposited by Ion-Beam Sputtering
Authors: Wang Y. , Cui F.Z. , Li W.Z. , Fan Y.D.
Published: March 2011

Fe/Mo multilayers, with varied Fe single layer thickness, tF, and Mo single layer thickness, tMO, were deposited by using a focusing ion-beam sputtering technique. Their structural and magnetic properties were studied. The periodic modulated structure was observed for all samples. An enhancement of magnetization over the value of bulk Fe was noticed for some samples. The change of lattice spacing of Fe layers, as a result of compress stress in the film plane, was considered to be responsible for the increase of the magnetization for Fe/Mo multilayers.
Absorption of Radiation by Magnetic Superlattices
Authors: LePage J.G. , Camley R.E.
Published: March 2011

We calculate the absorption of infra-red radiation by a magnetic superlattice composed of alternating ferromagnetic films. Although the films are ferromagnetic, the interfacial interaction is antiferromagnetic (i.e. Fe/Gd or Co/Gd). As has been shown previously, such a system can exist in several distinct phases, and we calculate the power absorption for these different phases. The spin wave modes of the system were found and used to construct a Green's function via an eigenvector expansion. The incoming radiation was modeled as an oscillating magnetic field which was assumed to decay into the material. Given this driving field, the Green's function yields the response of the system. Our results indicate that a simple absorption measurement can be used to probe for surface and bulk magnetic phase transitions. Additionally, we can find the response of the system to a spatially uniform driving field and thus calculate the local susceptibility. We discuss the possibility of using such a susceptibility to find dipole-exchange modes in magnetic superlattices.
Perpendicular Magnetic Anisotropy of Pd/Co and Related Multilayers
Authors: Tsunashima S. , Nakamura K. , Takahashi H. , Fukatsu S. , Uchiyama S.
Published: March 2011

Multilayer films consists of noble metal (Pd, Pt, Cu, Au, PdSi) and transition metal(Co, Ni, PdCo, PtCo, CoZr) layers were prepared by rf sputtering method on glass and/or MgO single crystal substrates. The perpendicular magnetic anisotropy was examined in relation to the magnetostriction, lattice misfits, crystallinity and crystal orientations. The results suggest that the perpendicular magnetic anisotropy in noble metal/PdCo alloy multilayers originates from the magnetoelastic energy of the PdCo layers under a stress due to the lattice misfits. In both Pd/Co and Pd/Ni multilayers, the anisotropy was found to depend on the crystal orientation, and the dependence is discussed from the view point of the magnetoelastic surface anisotropy.
Optical and Magneto-optical modeling of Ultra-thin Film Multilayers
Authors: McGahan William A , He Ping , Woollam John A
Published: March 2011

A Method for calculation of the optical and magneto-optical response of multilayered structures in which the layers are atomically thick is presented. The method can be used to calculate the response of any flim which has arbitrary compositional varaiation in the direction normal to the film plane as well. Calculations are presented for Tb/Co compositionally modulated alloys.
Spin-Polarized Eels on Ultrathin FCC Co Layers on CU(100)
Authors: Kamper K.-P. , Abraham D.L. , Hopster H.
Published: March 2011

The magnetism and the electronic structure of fcc Co films epitaxially grown on Cu(100) was investigated by spin polarized electron energy loss spectroscopy. Films above 2 atomic layers thickness show ferromagnetic order above room temperature with the magnetization in the plane. An exchange splitting of 0.8 eV and a Stoner gap of 300 meV is found. Films thinner than 1.6 layers do not show remanent magnetization above 80 K. No evidence for enhanced moments in monolayer films is found.
Preparation Of Zirconium Diphosphonate-Phosphites With A Narrow Distribution Of Mesopores.
Authors: Alberti G. , Costantino U. , Vivani R. , Zappelli P.
Published: March 2011

The presence of H3PO3 in the synthesis of zirconium diphosphonates in dimethylsulfoxide, other than the expected dilution of the pillars, which in turn gives rise to a certain degree of microporosity, may also induce the formation of a high percentag. of mesopores. E.g., compounds with high surface area(300–500 m2 /g) of which 60–70% is due to mesopores with diameters 20–40 Å and the remaining is due to micropores, were obtained. It was furthermore found that the distribution of the mesopores was fairly narrow. Compounds with micropores <3 Å and mesopores of 20–30 Å behave in practice as pure and narrow mesoporous solids;they are therefore of great interest as new molecular inorgano-organic sieves.
Photoreduction Of Methylviologen In The Interlayers Of Some Layered Titanates And Niobates
Authors: Nakato Teruyuki , Sugahara Yoshiyuki , kuroda Kazuyuki , Kato Chuzo
Published: March 2011

Methylviologen dication was intercalated to some layered semiconducting oxides, and the photoinduced electron transfer between the hosts and the guest was investigated. K4 Nb6O17, H2 Ti4O9, and HTiNbO5 were used as the layered oxides. The arrangements of methylviologen in the interlayers were deduced from the XRD results. UV irradiation of the intercalation compounds caused electron transfer from the hosts to the guest to form methylviologen radical cations. The radical cations were stable within a few minutes even in the presence of oxygen, and the decaying rates altered with the hosts. The difference was discussed on the basis of the structure of the intercalation compounds.
Intercalation Of Layered V2O5 Xerogel With Polymers
Authors: Kanatzidis M. G. , Wu C.-G. , Liu Y.-J. , DeGroot D. C. , Schindler J. L. , Marcy H. O. , Kannewurf C. R.
Published: March 2011

The intercalation properties of the layered V2O5 xerogel towards conductive polymers are described. The systems intercalated with polyaniline show post-intercalative redox polymerization caused by ambient oxygen to give products with enhanced conductivity. For the first time the role of oxygen in this intercalation reaction has been unequivocally identified. We also report the synthesis and some properties of a new intercalation compound in which the guest species is poly(ethylene oxide), an insulating polymer.
Reduction of Cu2+ and Ni2+ In Zeolite Y Using Polyol Process: A New Approach In The Preparation Of Metal Supported Catalysts
Authors: Malla P. B. , Ravindranathan P. , Komarneni S. , Breval E. , Roy R.
Published: March 2011

Zeolite NaY was exchanged with three levels of Cu2+ and Ni2+ ions which were subsequently reduced in ethylene glycol (polyol process) at 195° C. This process effectively reduced the transition metal ions to zerovalent forms and the degree of reduction was dependent on the amount of exchange and the location of transition metal ions. Polyol process was found to be more efficient in reducing these ions located in zeolite cages than commonly used molecular hydrogen. Comparison of reduction behavior of Cu2+ and Ni2+ ions indicated that better metal dispersion in NaY can be achieved for Ni2+ than Cu2+ by the polyol process.
Designing Zeolites As Novel Precursors To Electronic Ceramics
Authors: Corbin David R. , Parise John B. , Chowdhry Uma , Subramanian M. A.
Published: March 2011

The decomposition of zeolites is a novel route for the synthesis of aluminosilicate-based ceramic materials. Zeolites offer a number of advantages as ceramic precursors which allow the formation of dense ceramics at lower temperatures than by conventional methods. Using various cation-exchanged zeolites, ceramics and ceramic composites containing anorthite (CaAl2Si2O8). mullite (Al6Si2O11) cordierite (Mg2Al4Si5O18). celsian (BaAl2Si2O8), and ß-spodumene (LiAlSi2O6) have been formed. Using Extended X-ray Absorption Fine Structure (EXAFS), we have studied the reconstructive transformation of strontium-exchanged zeolite A to Sr-anorthite and have shown that the primary coordination of strontium remains intact during conversion.
Preparation Of Ceramic Molecular Sieve Membranes
Authors: Geus E.R. , Schoonman J. , van Bekkum H.
Published: March 2011

The preparation of a composite ceramic membrane consisting of large silicalite (MFI-type) crystals and a gas tight lead-boron silicate glaze is reported on. A one single crystal containing membrane model was prepared to establish the zeolite stability after each preparative step.
Atomic Force Microscopy Of Micron Size Silicalite Crystals
Authors: Rasch P. , Heckl W. M. , Deckman H. W. , Häberle W.
Published: March 2011

We have imaged micron sized silicalite crystals with an atomic force microscope (AFM). High resolution images taken in the repulsive mode show a periodic pattern that locally has a symmetry and periodicity which can be mapped onto the expected image looking along the [010] direction. Extra spots, however, appear in the image in regions which should correspond to channels exposed at the surface. These extra spots are attributed to multiple tip effects which should not affect the ability to detect long range ordering. On a scale length of ˜ 3 – 5 unit cells, the ordering in images deviates from that expected for a perfect crystal. This may be due to imperfections in the ordering at crystal surfaces. One other important aspect of the surface crystallography is revealed in low resolution scans where definite steps / grooves in the exposed surface are seen. The results are discussed in terms of the potential of AFM as a probe of surface crystallography.
Cracking And Aromatization Of Butanes Over ZSM-5 Zeolites
Authors: Ono Yoshio , Kanae Kunihiko , Osako Kazuaki , Nakashiro Katsumi
Published: March 2011

The transformation of butanes over H-ZSM-5, Zn-ZSM-5, and Ga-ZSM-5 at 773 K were studied with special emphasis on the activation mechanism of butanes. Over H-ZSM-5, butanes undergo cracking exclusively by a carbonium-ion mechanism at low conversion levels. At higher conversion levels, the activation by a hydride-transfer mechanism are involved. The loading of Zn and Ga greatly enhances the dehydrogenation of starting alkanes as well as intermediate alkenes. The loading of the metal cations promotes also the cracking, especially in the case of isobutane. The synergetic action of the metal cations and protons is proposed as a mechanism of alkane dehydrogenation.
Selective Oxidation Of Hydrocarbons By Cobaltsubstituted Aluminophosphate Molecular Sieves
Authors: Maroni Victor A. , Iton Lennox E.
Published: March 2011

The Co(III) form of cobalt-substituted aluminophosphate molecular sieves, Co(III)-APOs, was found to be a selective oxidant for a variety of organic and inorganic compounds. At relatively low temperatures (20 to 100°C), alcohols are converted to aldehydes and ketones, benzene becomes a dimer radical cation, amines are transformed to imines, and NO is oxidized to NO+. There is also evidence that Co(III)APOs activate the C-H bonds of methane at higher temperatures (400–500°C). Accompanying all these reactions is a clearly observable change of color from the yellow of the Co(III) form to the blue of the Co(II) form.
Strain Relief and Defect Formation in High Dose Oxygen Implanted Silicon
Authors: Venables D. , Jones K. S. , Namavar F. , Manke J. M.
Published: March 2011

Lattice strain and defect formation in oxygen implanted silicon (SIMOX) were investigated as a function of dose and annealing conditions by high resolution x-ray diffraction and transmission electron microscopy. X-ray rocking curves revealed the presence of two distinct strained layers. Self-interstitial clusters and oxygen interstitials gave rise to a buried strain layer in unidirectional tension centered around the projected range at low doses (l×1016 and 3×1016 cm−2. As the dose was increased to 1×1017 and 3×1017 cm−2 a supersaturation of vacancies near the surface produced a second strain layer with a unidirectional lattice contraction at the wafer surface. Annealing at 900°C, 0.5 hr. reduced this surface strain as the defects coarsened into observable cavities. The development of cavities upon annealing was used in a sequential implantation and low temperature annealing process to produce low threading dislocation density SIMOX. Possible mechanisms for threading dislocation formation are discussed.
Feasibility of Simox Material Quality Determination Using Spectroellipsometry: Comparison With Raman And Planar View Transmission Electron Microscopy
Authors: Crean G. M. , Lyncrt S. , Greef R. , Stoemenos J. , Rossow U. , Richter W.
Published: March 2011

One of the most promising silicon on insulator (SOI) fabrication techniques under development is Separation by IMplanted OXygen (SIMOX) substrates. The objective of this paper is to evaluate the feasability of employing spectroscopic ellipsometry (SE) for the determination of SIMOX substrate quality. Defect density measurements obtained from planar view transmission electron microscopy (TEM) studies are presented and concur with the Raman experimental results. The need for the development of a more sophisticated ellipsometric optical response model to mirror the complexity of the annealed Si overlayer microstructure is demonstrated.
The Energy Dependence of Ion Damage in A1xGa1−xAs/GaAs HETErostructures and The Effects of Implanted Impurity
Authors: Cullis A. G. , Jacobson D. C. , Polman A. , Smith P. W. , Poate J. M. , Whitehouse C. R.
Published: March 2011

Bombardment damage produced by Si+ ions in AlxGa1−xAs/GaAs layer structures has been studied using transmission electron microscopy and ion channeling and backscattering spectrometry. The damage resistance of A1xGa1−xAs alloy layers increases with Al concentration. In particular, by comparison of complementary Si+ ion doses yielding similar nuclear displacement densities at 150keV and 2MeV bombardment energies, it is demonstrated for the first time that the local concentration of implanted Si impurity is likely to be a significant factor in controlling lattice damage build-up, especially for the highest Si+ ion implantation doses. It is also shown that, in a manner analogous to A1As, the alloy layers can confer a significant protection from ion damage upon adjacent, epitaxially-bonded narrow zones of crystalline GaAs.
Anisotropic Damage Production at ION Irradiated GaAs/AlAs Interfaces
Authors: Klatt J. L. , Alwan J. , Coleman J. J. , Averback R. S.
Published: March 2011

Ion beam mixing and damage production at GaAs-AlAs interfaces was studied by Rutherford backscattering and channeling methods. It was observed that the general features of the intermixing of GaAs with AlAs at 100K are typical of that in other semiconductor and metallic systems but that the damage production is not. The GaAs layers amorphize at a very low ion dose whereas the AlAs layers are very resistant to amorphization. Damage in the AlAs begins at one interface of the GaAs and grows through the AlAs layer, but damage at the other interface never nucleates. The ratio of nuclear to electronic stopping influences the growth of the damage zone.
Characterization of Novel Emissions in Mg+ -Implanted InP
Authors: Iida Tsutomu , Makita Yunosuke , Niki Shigeru , Yamada Akimasa , Asakura Hisao , Kimura Shinji , Obara Akira , Uekusa Shin-ichiro
Published: March 2011

Photoluminescence (PL) measurements have been carried out as a function of temperature and of excitation power on heavily magnesium (Mg) implanted ultra-pure indium phosphide (InP) with a dose concentration, [Mg], ranging from l×lO15cm-3 to 3×1020cm−3. Several undefined emissions have been observed; a strong emission, Z, emerges near the band-acceptor emission for [Mg]= 3×1020cm−3 and two novel emissions, Y1 and Y3 appear below the energy of donor-acceptor pair emission for [Mg] smaller than 3×1018cm−3. In order to obtain more explanation on such emission, temperature and excitation power dependence of the emissions were investigated. Temperature dependent PL experiments revealed that Z is composed of three emissions named ZA, ZBand ZC. Measured activation energies suggest Z represents a pair type transition associated with Mg acceptors. While, Y1 and Y3 emissions are attributed to donor-acceptor type transition because of a significant blue-shift with increasing excitation power.
Mesotaxy Layers of IrSi3 in (111)Si Formed by MeV ION Implantation
Authors: Short K. T. , White Alice E. , Eaglesham D. J. , Jacobson D. C. , Poate J. M.
Published: March 2011

Iridium has been implanted at 1MeV and 500keV in the dose range 1 to 3×1017/cm2 at 525°C to form a buried Ir-rich region ∼ 2500Å below the surface in (111)Si. Samples were annealed at temperatures in the range 600°C to 1200°C to form buried IrSi3 layers. Rutherford backscattering and channeling analysis in conjunction with transmission electron microscopy were used to study the formation and the alignment of the IrSi3 layer to the silicon host as a function of annealing. For a dose of 2×1017 Ir/cm2, stoichiometric IrSi3 formed beneath ∼ 2000Å of Si after annealing to 1100°C. The IrSi3 layer was aligned with the Si substrate with Xmin ∼12%, but a band of precipitates remained either side of the main layer.
Formation of Buried Epitaxial Si-Ge Alloy Layers in Si <100> Crystal by High Dose Ge ION Implantation
Authors: Yu Kin Man , Brown Ian G. , Im Seongil
Published: March 2011

We have synthesized single crystal Si1−xGex alloy layers in Si <100> crystals by high dose Ge ion implantation and solid phase epitaxy. The implantation was performed using the metal vapor vacuum arc (Mevva) ion source. Ge ions at mean energies of 70 and 100 keV and with doses ranging from 1×1016 to to 7×1016 ions/cm2 were implanted into Si <100> crystals at room temperature, resulting in the formation of Si1−xGex alloy layers with peak Ge concentrations of 4 to 13 atomic %. Epitaxial regrowth of the amorphous layers was initiated by thermal annealing at temperatures higher than 500°C. The solid phase epitaxy process, the crystal quality, microstructures, interface morphology and defect structures were characterized by ion channeling and transmission electron microscopy. Compositionally graded single crystal Si1−xGex layers with full width at half maximum ∼100nm were formed under a ∼30nm Si layer after annealing at 600°C for 15 min. A high density of defects was found in the layers as well as in the substrate Si just below the original amorphous/crystalline interface. The concentration of these defects was significantly reduced after annealing at 900°C. The kinetics of the regrowth process, the crystalline quality of the alloy layers, the annealing characteristics of the defects, and the strains due to the lattice mismatch between the alloy and the substrate are discussed.
Ion Implantation of High Doses of Co in Si1−xGex Alloys
Authors: Lauwers A. , Maex K. , Vandervorst W. , Brijs G. , Poortmans J. , Caymax M. , Vanhellemont J. , Petersson S.
Published: March 2011

The implantation of high doses of Co in Si1−xGex alloys is investigated for several Ge concentrations. The aim of this work is to monitor phase formation, layer formation and crystalline structure of the layers. The samples are evaluated by RBS, SIMS, TEM and sheet resistance measurements. Similar as for the implantation of high doses of Co in Si, buried layer formation of CoSi2 in the Si1−x Gex alloy is observed with a concommitant expulsion of Ge out of the silicide layer.
Process and Simulation of TiSi2/n+/p Silicon Shallow Junctions
Authors: Wu Ying , Savin W. , Fink T. , Ravindra N. M. , Lareau R. T. , Pfeffer R. L. , Yerke L. G. , Wrenn C.
Published: March 2011

Experimental analysis and simulation of the formation and electrical characterization of TiSi2/+/p-Si shallow junctions are presented here. The formation of shallow n+-p junction, by ion implantation of As through Ti films evaporated on p-Si substrates followed by Rapid Thermal Annealing (RTA) and conventional furnace annealing has been performed in these experiments. Structural techniques such as Secondary Ion Mass Spec-troscopy (SIMS) and Rutherford Backscattering (RBS) experiments have been employed to characterize these devices. RUMP simulations were used to analyze and interpret the RBS data. Current-voltage characteristics have been simulated using PISCES simulator.
A Novel Process to Form Epitaxial Si Structures With Buried Silicide
Authors: Erokhin YU. N. , Grotzschel R. , Oktyabrski S. R. , Roorda S. , Sinke W. , Vjatkin A. F.
Published: March 2011

The interaction during low temperature thermal annealing of metal atoms from a Ni film evaporated on top of Si structures with a buried amorphous layer formed by ion implantation has been investigated. Rutherford Backscattering Spectrometry (RBS)/channeling, cross-sectional transmission electron microscopy (XTEM) and X-ray microanalysis were used to determine structures and compositions. It is shown that the combination of such silicon properties as the increased rate of silicidation reaction for amorphous silicon with respect to the crystalline one in combination with high metal atom diffusivity leads to formation of buried epitaxial Ni silicide islands at the interface between the amorphous and the top crystalline silicon layers. During thermal annealing at temperatures as low as 350° C, these islands move through the a-Si layer leaving behind epitaxially recrystallized Si.
Temperature Dependence of Ar Sputtering of CoSi2 Thin Films on Si and SiO2
Authors: Hong Q. Z. , Harper J. M. E.
Published: March 2011

The temperature dependence of 300 eV argon ion sputtering of CoSi2 thin films in the range 50–600°C has been investigated. At temperatures above 400°C, the etch rate of CoSi2 on Si is significantly reduced, while the underlying Si reacts with the Co atoms diffusing from the silicide surface. As a result, the silicide layer effectively moves into the substrate during Ar bombardment. During sputtering of CoSi2 on Sio2, the thickness of the silicide layer decreases almost linearly with bombarding time until all the silicide is removed. Similar behavior is observed in low temperature sputtering of CoSi2 on (100) Si and evaporated Si. However, at elevated temperatures (400°C< <600°C), sputtering of CoSi2 on Si undergoes two consecutive stages. During the initial stage, the thickness of the silicide layer decreases at the same rate as that of the silicide on SiO2, and is accompanied by an enrichment in Co concentration near the surface. During the second stage, the etch rate of the silicide is reduced to only one third of the rate during the initial stage.
Ion Beam-Induced Amorphization of (Mg, Fe)2SiO4 Olivine Series: An In Situ Transmission Electron Microscopy Study
Authors: Wang L. M. , Ewing R. C.
Published: March 2011

Effects of ion beam irradiation of five members of the (Mg, Fe)2SiO4 olivine series, from synthetic pure fayalite (Fe2SiO4) to naturally occurring (Mg0.88Fe0.12)2SiO4, have been studied by in situ transmission electron microscopy (TEM). Under 1.5 MeV Kr+ ion room temperature irradiations, all of the samples have been amorphized. The critical amorphization dose or the total collision energy loss required for amorphization increased rapidly with the increasing Mg:Fe ratio which coincides with an increasing melting temperature (bond strength) and an increasing average bond ionicity. A 400 keV He+ ion irradiation of (Mg0.88Fe0.12)2-SiO4, which mainly results in ionization energy loss in the sample, did not cause amorphization even at a much higher dose rate and a much higher final dose. This indicates nuclear interactions (collisions) are primarily responsible for ion beam induced amorphization. Also, high resolution electron microscopy (HREM) images of the defect structure at a low ion dose have been obtained and compared with the displacement cascade structure generated by computer modelling.
In-Situ Tem Observations of Electron Beam-Stimulated Reactions in NiO Under Oxidizing and Reducing Atmospheres
Authors: Buckett M. I. , Marks L. D.
Published: March 2011

ABSTRACT:L: NiO surfaces have been the subject of numerous investigations using a wide variety of techniques, including transmission electron microscopy (TEM). The findings, however, remain inconclusive regarding the relative contributions of irradiation effects such as ballistic erosion, electron-stimulated desorption (ESD) and electron-stimulated reaction (ESR), especially at incident electron energies exceeding 100 keV. In earlier studies it was suggested that the surface environment played a significant role in the radiation damage process. In this study, the effect of the surface environment is further illustrated by in-situ experiments in controlled sample environments. NiO surfaces were irradiated with electrons, ranging in energy from 3 keV to 300 keV, and examined in-situ under ultra-high vacuum (UHV) conditions (10−10 Torr), as well as in controlled oxidizing (oxygen) and reducing (CO) atmospheres. The nature of the surface reactions and their contribution to the overall radiation damage process in the various energy regimes is examined.
Characterization of Ion Irradiated Zirconia-Yttria Films
Authors: Huang N. K. , Feng Z. R. , Xiong Z. K. , Wang D. Z. , Wang P. L.
Published: March 2011

Zirconia-yttria films containing 8.0wt% Y2O3 were prepared on a Si substrate with r.f. magnetron sputtering deposition followed by 170 KeV Ar+ ion irradiation at room temperature. The characterization of these zirconia-yttria films with different ion bombarding doses has been studied by XRD, XPS and AES. It was found that all the films consisted of three portions, the amorphous films deposited with r.f. magnetron-sputtering were partially crystallized and nontransformable tetragonal (T') phase was detected after Ar+ ion bombardment of a dose of 1×1016 ion/cm2, and the oxidized states of Zr3d, Y3d and Ols peaks of XPS were observed under the conditions of argon ion bombardment of different doses.
MeV Self Ion Beam Induced Amorphisation of Silicon Carbide Surfaces and Its Effect on Their Trdbomechanical Propertdzs
Authors: Sood D. K. , Nath V. C. , Xi Yang
Published: March 2011

Amorphisation of sintered SiC by bombardment with self (C, Si) ions has been studied. Ion doses ranged from 1×1015 to 1×1017 ions/cm2; and ion energy was varied from 0.09 to 5 MeV. Amorphisation was detected by micro-focus Raman scattering. Tribomechanical properties-friction and wear were studied with a high precision pin (steel ball) and disc (implanted) machine. Results show substantial improvements in friction and wear, which persist to a large number of cycles. Tribomechanical properties are shown to correlate with surface amorphisation and carburisation. Carbon ions are found to be much more effective than Si ions (with similar damage distributions) in reducing friction and wear.
Vacancy-type and electrical defects in amorphous silicon probed by positrons and electrons
Authors: Roorda S. , Hakvoort R. A. , van Veen A. , Stolk P. A. , Saris F. W.
Published: March 2011

Amorphous Si has been investigated by variable-energy positron annihilation spectroscopy (PAS) and lifetime measurements of optically generated free carriers. The density of positron-trapping defects can be reduced by thermal annealing at 500°C. Simultaneously, the density of bandgap states is reduced as indicated by an increased photocarrier lifetime. Hydrogen, implanted and annealed at 150°C, leads to an increased photocarrier lifetime and reduced positron trapping. It appears that (some of) the electrical defects are associated with positron-trapping, and therefore possibly vacancy-type, structural defects. Finally, both methods have been used to detect small amounts of ion irradiation damage in amorphous Si.
Stability of Uranium Silicides During High Energy Ion Irradiation
Authors: Birtcher R. C. , Wang L. M.
Published: March 2011

Changes induced by 1.5 MeV Kr ion irradiation of both U3Si and U3Si2 have been followed by in situ transmission electron microcopy. When irradiated at sufficiently low temperatures, both alloys transform from the crystalline to the amorphous state. When irradiated at temperatures above the temperature limit for ion-beam amorphization, both compounds disorder, with the Martensite twin structure in U3Si disappearing from view in TEM. Prolonged irradiation of the disordered crystalline phases results in nucleation of small crystallites within the initially large crystal grains. The new crystallites increase in number during continued irradiation until a fine grain structure is formed. Electron diffraction yields a powder-like diffraction pattern that indicates a random alignment of the small crystallites. During a second irradiation at lower temperatures, the small crystallizes retard amorphization. After 2 dpa at high temperatures, the amorphization dose is increased by over twenty times compared to that of initially unirradiated material.
Role of Chromium in High-Dose, High-Rate, Elevated Temperature Nitrogen Implantation of Austenitic Stainless Steels
Authors: Williamson D. L. , Ivanov I. , Wei R. , Wilbur P. J.
Published: March 2011

In order to help establish the role of Cr in high-dose, high-dose-rate, elevated temperature N implantation of austenitic (fcc) stainless steels, similar implantations into fee Ni80Fe20 and Ni80Cr20 alloys have been made and characterized by Auger depth profiling and X-ray diffraction. For the Ni-Fe alloy a shallow layer fcc(∼ 0.2 μm) containing an ordered fee γ'-(Ni0.8Fe0.4)4N phase is induced. In contrast, for the Ni-Cr alloy a much thicker N-containing layer (∼ 0.2 μm) is produced consisting primarily of a high-N solid solution fee phase. The fractions of the implanted N retained in Ni-Fe and Ni-Cr were approximately 10 and 100%, respectively. The mechanisms by which Cr is promoting the deep migration and high retention of N in solid solution are proposed.
Photoluminescence of Erbium in Amorphous Silicon: Structural Relaxation and Optical Doping
Authors: Custer J. S. , Snoeks E. , Polman A.
Published: March 2011

Photoluminescence of erbium in ion-implanted amorphous Si has been observed after annealing at 400°C. In addition, a broad band of luminescence attributed to intrinsic defects in amorphous Si is present. The background level steadily increases with increasing anneal temperature. The fluorescence lifetimes of either the Er or the background in all samples are ≤150μsec.
Metastable Phase Formation in the Y-TI System by Ion Mixing
Authors: Lai S. L. , Zhang Z. J. , Ding J. R. , Liu B. X.
Published: March 2011

Amorphization behavior was studied for the Y-Ti system, which has rather positive heat of formation being around + 22 kJ/mol, by room temperature 360 keV xenon ion mixing of YxTi100−xmultilayered films to various doses, ranging from 7×1014 to 1×1016 xe/cm2 Single and uniform amorphous phase was obtained in a narrow composition region, i.e. x=65 to 75, after ion mixing to the relevant doses. Moreover, a metastable fee crystalline Y-Ti phase was observed, for the first time, in this system. The crystalline lattice constant of the metastable phase was determined to be 4.012 Å. The re-crystallization temperature of the formed amorphous alloy was found out to be 600°C by in situ transmission electron microscope annealing as well as by vacuum furnace experiments. Possible interpretation is also discussed by comparing the experimental results with those proposed models for predicting glass forming ability.
Al-Yb Amorphous Alloys Produced by Ion Mixing or Solid State Reaction
Authors: Liu B. X. , Ding J. R. , Che D. Z. , Zhang H. B.
Published: March 2011

We report, in this paper, three different ways of producing amorphous alloys in the Al-Yb system, (i) Al80Yb20multilayered films were readily amorphized by 180 keV xenon ion mixing at room temperature(RT) to a dose of 3×1015 Xe/cm2. (ii) When the dose went up to 1×1016 Xe/cm2 or higher, a metastable phase of hcp structure was formed. Interestingly, the hcp phase turned into amorphous after annealing at 500°C for about 10 minutes. (iii) Amorphous alloys were also formed by steady state thermal annealing of the Al-Yb multilayered films at about 450 °C for 20 minutes. The optimum amorphization range was found out by experiments to be 17 to 30 Yb at%, i.e., within this composition range, the multilayered films could entirely be amorphized by solid state reaction.

The recrystallization behavior of the amorphous alloys formed by different methods was also studied and the difference in this aspect was thought to relate to the structures resulting from different processing methods.

Possible explanation of the observed sequence of phase transition is also discussed.
Molecular Dynamics Simulation of Electron Irradiation-Induced Amortization of the Ordered Compound NiZr
Authors: Devanathan R. , Lam N. Q. , Sabochick M. J. , Okamoto P. R. , Meshh M.
Published: March 2011

We present the results of a molecular dynamics simulation of the crystalline-to-amorphous transformation in the ordered intermetallic compound NiZr, using embedded-atom potentials. It is found that NiZr can be amorphized by random atom exchanges as well as by the introduction of Frenkel pairs. In both cases, the shear elastic constants C44 and C decreased drastically and eventually became equal. The average shear elastic constant fell to about 40% of its original value. These results are in general agreement with experimental observations.
Nanoindentation Hardness of 17–4PH Stainless Steel Irradiated With 2.5 MEV PER Nucleon 20NE2+ Ions
Authors: Grummon D. S. , Schalek R. , Rachel T. , Schock H. , Ronningen R. M. , Mcharris Wm. C.
Published: March 2011

Direct ion implantation of radioactive isotopes, such as 7Be or 22Na, has recently been of interest as a means of surface layer activation for purposes of wear-rate measurement in material systems for which activation by conventional proton irradiation is ineffective. Though direct implantation doses anticipated for adequate wear measurement sensitivity are expected to be quite low (∼1012 cm−2), the potential for alteration of wear properties by ion damage cannot be ignored. The present work was designed to simulate 22Na implantation with non-radioactive 20Ne irradiations into specimens of 17–4PH stainless steel which had been deliberately heat treated to contain 98 vol% metastable martensite. Specimens were subjected to doses of 2×1012, 2×1013 and 2×1014 cm−2 of 20Ne2+, applied at a total energy of 50 MeV, giving a projected ion range (determined by TRIM-91 computations) of approximately 10 μm. Nanoindentation surface hardness traverses were conducted to detect any material softening which may have resulted from ion-solid interactions within the projected range. Though doses of > 1014 cm−2 produced a detectable softening (apparent as a dip in the hardness level corresponding to locations near the end of the ion range) the maximum dose for a negligible effect on nanoindentation hardness was found to be approximately 1013 cm−2, well above the doses anticipated for use in wear studies employing direct ion implantation of radioisotopes.
Fatigue of Aluminum Films Leading to Melting by Multiple Laser Pulses
Authors: Bernstein Joseph B. , Cohen Simon S. , Wyatt Peter W.
Published: March 2011

Repeated laser pulses at a single point on an aluminum thin film can reduce the power needed to melt or damage the surface as compared with CW application. This multi-pulse effect was found to depend on metal thickness and number of pulses, while being weakly dependent on the pulse length. This behavior appears to result from cumulative mechanical fatigue due to cyclic thermal stress in excess of the aluminum yield stress. This principle has been applied to cutting metal wires in microelectronic applications for deletive redundancy. The results suggest a significant advantage over CW laser application since the power needed to cut a metal wire is reduced by more than 70%, and 87% as compared to a single pulse.
XPS and FTIR Study of the Thin Polyimide Films Fabricated by Ionized Cluster Beam Deposition
Authors: Kim K. W. , Chae K. H. , Choi S. C. , Cho S. J. , Vahc Y. W. , Whang C. N. , Jung H. J. , Lee D. H. , LEE J. K.
Published: March 2011

The ionized cluster beam deposition (ICBD) technique has been employed to fabricate high-purity polyimide (PI) films. The pyromellitic dianhydride (PMDA) and oxydianiline (ODA) were deposited using dual ionized cluster beam (ICB) sources. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoemission spectroscopy (XPS) studies show that the bulk and surface chemical properties are very sensitive to the ICBD conditions such as cluster ion acceleration voltage and ionization voltage. At optimum ICBD conditions, the PI films have a maximum imidization and negligible impurities(∼;1% isoimide) probably due to the high surface migration energy and surface cleaning effect.