bluuebunny/crossref_metadata_2025_split huggingface dataset:
Depth of Origin of Secondary Ions: Suppression and Enhancement of Ions Upon Passage Through Overlayers.
Authors: Sack N. J. , Akbulut M. , Madey T. E. 
Published: April 2011

AbstractWe are investigating the transmission of low energy ions (<10 eV) through ultrathin films of condensed rare gases. Our goal is to address the issue of the depth of origin of secondary ions that desorb from solid surfaces under the impact of ionizing radiation, such as electrons, photons, or through ion sputtering. The secondary ions are produced by electron stimulated desorption (ESD) from a suitable substrate, such as an oxide or an adsórbate on a metal single crystal; the overlayer gas is condensed onto this substrate. The yield, energy and angular distributions of the ions are measured as a function of overlayer thickness. We find that 7 eV oxygen ions can be transmitted through rare gas films (Kr, Xe) several ML thick. In contrast, O+ is completely suppressed by 0.5 ML of H2O. Surprisingly, we find the F− yield to be 4 times higher in the presence of 1 ML of Xe, compared to the clean surface value, accompanied by a dramatic change in the ions’ angular distribution. We discuss a model which considers elastic scattering and charge transfer of the ions with rare gas atoms, as well as the structure of the surface and the electronic properties of the solid-vacuum interface.
Defect Formation by Single Ion Impacts on Highly Oriented Pyrolytic Graphite Observed by Scanning Tunneling Microscopy
Authors: Reimann K. P. , Bolse W. , Geyer U. , Von minnigerode G. , Lieb K. P. 
Published: April 2011

Abstract(0001) surfaces of highly oriented pyrolytic graphite (HOPG) were irradiated at 77K with 132Xe+ ions at energies between 50 keV and 900 keV. The ion fluences ranged between 1011 ions/cm2 and 1015 ions/cm2. Scanning tunneling microscopy (STM) was applied to image the irradiation induced defects at the surfaces. In case of orthogonal incidence and small ion fluence each incident ion induces one single hillock at the surface. These hillocks have typical lateral diameters of 2 nm and heights of several à. In many cases measurements of the hillocks with atomic resolution show disordered atomic arrangements. The hillocks are interpreted as the local volume expansion due to surface-near self-interstitials generated in the collision cascades of the ions. The high mobility of these interstitials parallel to the (0001) planes leads to a formation of interstitial clusters which cause the larger hillocks. Irradiation at an angle of incidence of 75° with respect to the surface normal effects a higher density of hillocks due to the higher number of recoils stopped in the uppermost lattice planes. The hillocks are arranged in chains which are aligned in the direction of the incident beam. Each of these chains marks a single collision cascade.
Thermal Stability Study of Oxygen Implanted Algaas/Gaas Single Quantum Well Structures Using PhotoreflectancE
Authors: Hughes P J , Li E H , Weiss B L , Jackson H E , Roberts J S 
Published: April 2011

AbstractThe effects of interdiffusion on the band structure of two MxGaUxAs/GaAs single quantum well (SQW) structures were studied using room temperature photoreflectance. Rapid thermal annealing of the SQW structures at temperatures of 800°C, 900°C and 1000°C for times up to 180 seconds resulted in limited interdiffusion. Low dose (1014 cm”2) oxygen implantation reduced the thermal stability of these structures where the extent of the interdiffusion was found to be greater for the implanted samples for identical annealing conditions.
Total Reflection X-Ray Fluorescence (TXRF)
Authors: Hockett R. S. 
Published: April 2011

AbstractTotal reflection X-Ray Fluorescence (TXRF) is a glancing x-ray analytical technique which is used primarily to measure surface metal contamination on semiconductor substrates. This is a review of Total reflection X-Ray Fluorescence (TXRF) applications for silicon semiconductor processing. In addition, some comments are made about the future of TXRF, and in particular, synchrotron radiation TXRF (SR-TXRF)
Elasticity Shear Modulus Modification By Impulsive Ion Implantation
Authors: Feugeas Jorge N. , Lambri O.A. , Grigioni G. , Sanchez G. , Povolo F. 
Published: April 2011

AbstractSamples of pure copper were argon ion irradiated using a Plasma Gun operated in the detonation mode. The irradiated copper samples were studied by means of the Mechanical Dynamical Spectroscopy technique.
The results show an anomalous behavior in the Elasticity Shear Modulus, consisting in an abrupt jump in its value at ∼840K, repeated in the running up as well as in the running down part of the temperature cycling. A Damping Peak at that temperature was also observed.
Improved Near Surface Heavy Impurity Detection by a Novel Charged Particle Energy Filter Technique
Authors: Ishibashi K. , Patnaik B.K. , Parikh N. R. , Tateno H. , Hunn J.D. 
Published: April 2011

AbstractAs the typical feature size of silicon integrated circuits, such as in VLSI technology, has become smaller, the surface cleanliness of silicon wafers has become more important. Hence, detection of trace impurities introduced during the processing steps is essential. A novel technique, consisting of a “Charged Particle Energy Filter (CPEF)” used in the path of the scattered helium ions in the conventional Rutherford Backscattering geometry, is proposed and its merits and limitations are discussed. In this technique, an electric field is applied across a pair of plates placed before the detector so that backscattered particles of only a selected energy range go through slits to strike the detector. This can be used to filter out particles from the lighter substrate atoms and thus reduce pulse pileup in the region of the impurity signal. The feasibility of this scheme was studied with silicon wafers implanted with 1×1014 and 1×1013 14pe/cm2 at energy of 35 keV, and a 0.5 MeV He+ analysis beam. It was found that the backscattered ion signals from the Si atoms can be reduced by more than three orders of magnitude. This suggests the detection limit for contaminants can be improved by at least two orders of magnitude compared to the conventional Rutherford Backscattering technique. This technique can be incorporated in 200–300 kV ion implanters for monitoring of surface contaminants in samples prior to implantation.
Mass Spectrometric Studies of Pulsed Laser Ablation: Existence of Rydberg State Atoms
Authors: Leuchtner Robert 
Published: April 2011

AbstractAn unusual aspect of the pulsed laser deposition (PLD) process is that highly oriented (sometimes epitaxial) films of complex, multicomponent materials can often be prepared at low substrate temperatures. It is argued, using a simple model, that the arrival of even minor quantities of electronically excited species (Rydberg atoms and ions) can significantly affect the local surface temperature of the growing film. The present study experimentally confirms the existence of these energetic components in an ablation plume using a specially-modified time-of-flight quadrupole mass spectrometer. Ions as well as long-lived, excited state (Rydberg state) atoms were detected from laser ablation from a YBa2Cu307-5 (YBCO) target. Multiple peaks in the TOF profiles appear to derive from electron/ion recombination from higher charged species; the high kinetic energies observed are explainable from simple electrostatics involving localized holes trapped on the target surface.
Real-Time Monitoring for Laser Surface Cleaning
Authors: Lu Y.F. , Hong M.H. , Aoyagi Y. 
Published: April 2011

AbstractReal-time monitoring of surface cleanness in laser dry cleaning was investigated by monitoring the acoustic waves emitted from the substrate surface under pulsed laser irradiation. It is found that the acoustic wave from the surface under laser irradiation can reflect the surface condition, i.e., the surface cleanness. Besides the surface condition, the acoustic waveforms also depend on the substrate materials and laser pulse energies (intensities). The frequency spectrum obtained from the Fourier transform can provide clear indication for different surface cleanness. Removing of surface contaminants can generally result in weaker laser-induced acoustic wave and change in the frequency spectrum. The surface cleanness, therefore, can be monitored in real-time by detecting the amplitude and frequency of the acoustic wave during the laser cleaning process. This phenomenon provides the laser cleaning technique a real-time feedback during the cleaning process.
Exafs Studies of the Difference in Local Structure of Various Tantalum Oxide Capacitor Films
Authors: Kimura H. , Mizuki J. , Kamiyama S. , Suzuki H. 
Published: April 2011

AbstractThe extended x-ray absorption fine structure (EXAFS) above the Ta L3-edge on tantalum oxide capacitor films has been measured. Four kinds of tantalum oxide films were studied: as-deposited (amorphous), dry 02 annealed (crystalline), 02-plasma annealed (amorphous) and 2-step (02-plasma + dry O2) annealed (crystalline). From EXAFS analysis, differences in the local structures of tantalum oxide capacitor films, in terms of oxygen deficiency around Ta, were observed in the various annealed films. The leakage current characteristics of tantalum oxide capacitors correspond with the differences in the local structures around Ta. The discussion looks at the relationship between the leakage current characteristics and the local structures around Ta.
Ion Beam Sputter Deposition of Refractory Metal Oxides
Authors: Kempf B.E. , Dinges H.W. , PÖcker A. 
Published: April 2011

AbstractOxides of hafnium, niobium, tantalum, and zirconium are deposited by ion beam sputtering of the pure metal targets using CO2 as working gas. The resulting thin films are amorphous, featureless smooth and of excellent adherence to semiconductor substrates. Despite a certain content of carbon they are highly transparent in the visible and near infrared wavelength range as determined by spectroscopic ellipsometry. Their wide range of refractive indices makes them suitable for multilayer optical filter design.
Gamma Ray Processing of ZnGeP2: A Nonlinear Optical Material for the Infrared
Authors: Schunemann P.G. , Drevinsky P.J. , Ohmer M.C. 
Published: April 2011

AbstractZinc germanium phosphide, an important frequency-conversion material for producing mid-infrared lasers, is plagued by a defect-related absorption band extending from the fundamental edge (0.62 microns) to ∼3 microns. The level of absorption varies with melt composition, and can be reduced by post-growth annealing treatments. In these experiments, further reduction of the near-band-edge absorption was achieved by irradiating with 1.173 MeV and 1.3325 MeV gamma rays. A 40 kiloCurie “Co source was used to irradiate a series of crystals at an average flux of 4.8x10s rads/hr to cumulative doses up to 3.91xl010 rads. The absorption coefficient in the near-infrared was reduced by nearly a factor of two, and the penetration depth of the ionizing radiation was sufficient to uniformly reduce the absorption in the largest samples tested (up to 7x8x23mm3). The loss coefficients achieved at 1 micron (4.28cm∼l) and at 2.05 microns (0.19cm1) are lower than the best results achievable by conventional thermal annealing alone. No saturation effects or absorption increases at longer wavelengths were observed.
Laser assisted molecular beam deposition of thin films of polymeric copperphthalocyanine and their characterization
Authors: Wijekoon W.M.K.P. , Xia Ping , Prasad P.N. , Garvey J.F. 
Published: April 2011

AbstractThin films of polymeric copperphthalocyanine were fabricated via laser assisted molecular beam deposition by reacting the laser ablated plasma flume of a copper target with 1,2,3,5-tetracyanobenzene entrained within a molecular beam expansion. 1,2,4,5-Tetracyanobenzene entrained within a helium carrier gas was supersonically expanded to intercept a second expansion containing gas-phase aggregates of metallic copper. These two molecular beams met at a point between the target and the substrate producing gas phase polymeric copperphthalocyanine which could be then directly deposited as a thin film coating on room temperature substrates. Such films were characterized by scanning electron microscopy and uv-visible, infrared and x-ray photoelectron spectroscopic techniques. Optical spectra of films dissolved in H2S04 solutions reveal that small amounts of monomeric copperphthalocyanine is also present in the grown films. All the copper in these films is found to be in Cu+2 ionization state.
Fabrication and Modification of Metal Nanocluster Composites Using Ion and Laser Beams
Authors: Haglund R.F. , Osborne D.H. , Magruder R.H. , White C.W. , Zuhr R.A. , Townsend P.D. , Hole D.E. , Leuchtner R.E. 
Published: April 2011

AbstractMetal nanocluster composites have attractive properties for applications in nonlinear optics. However, traditional fabrication techniques — using melt-glass substrates — are severely constrained by equilibrium thermodynamics and kinetics. This paper describes the fabrication of metal nanoclusters in both crystalline and glassy hosts by ion implantation and pulsed laser deposition. The size and size distribution of the metal nanoclusters can be modified by controlling substrate temperature during implantation, by subsequent thermal annealing, or by laser irradiation. We have characterized the optical response of the composites by absorption and third-order nonlinear-optical spectroscopies; electron and scanning-probe microscopies have been used to benchmark the physical characteristics of the composites. The outlook for controlling the structure and nonlinear optical response properties of these nanophase materials appears increasingly promising.
A Comparative Study of Pulsed Laser And Electron Beam Irradiation Effects In Fe81B13.5Si3.5C2 Glass
Authors: Sorescu Monica , Knobbe E. T. , Barb D. 
Published: April 2011

AbstractSamples of Fe81B13.5Si3.5C2 metallic glass were irradiated with a pulsed excimer laser (λ=308 nm, τ=10 ns), with a high-energy electron beam (W=7 MeV), and with low-energy electron beams (W=30 and 50 keV). Irradiation-driven changes in the magnetic anisotropy and phase equilibrium of alloy samples were studied by Mössbauer spectroscopy and scanning electron microscopy. Pulsed-excimer-laser irradiation was found to induce controlled magnetic anisotropy without onset of bulk crystallization in the Fe81B13.5Si3.5C2 amorphous system. High-energy electron-beam irradiation determined an out-of-plane magnetic anisotropy due to changes in the chemical short-range order. Low-energy electron-beam irradiation resulted in the formation of crystalline regions, in which α-Fe, Fe-Si, Fe3B, Fe2B, and clusters of γ-Fe were identified. Interpretation of these results is given in terms of radiation-enhanced diffusion.
Sintering of Textured YBa2Cu307-x Under Intensive 60Co Gamma Irradiation
Authors: Ibragimova Elvira M. , Gasanov Eldar M. , Kalanov Makhmud , Kirk Marquis A. , Goretta Ken C. 
Published: April 2011

AbstractA study of structural and superconducting characteristics of YBa2Cu307-x ceramics sintered after and in the course of gamma-irradiation is reported. Using X-difraction and SEM analyses and transport measurements, it has been shown that mainly the subsurface layer of crystallites and intergrain contacts are affected by the irradiation by means of sorption/desorption of oxygen and ordering/disordering in oxygen sublattice, which depends on gamma dose rate and dose. The irradiation provides the sintering process with an additional superthermal energy to form the orthorhombic well-ordered structure and to obtain dense ceramics possessing strong intergrain contacts and improved and stable superconducting properties
Interaction of Pt Films With ZnO(0001) and ZnO(0001)
Authors: Petrie W.T. , Vohs J.M. 
Published: April 2011

AbstractThe growth, structure, and electronic properties of Pt films supported on the (0001) and (0001) surfaces of ZnO were investigated using high-resolution electron energy-loss spectroscopy (HREELS) and low-energy electron diffraction (LEED). Vapor-deposited Pt films were found to grow in a layer-by-layer fashion on both surfaces and exhibited hexagonal LEED patterns. HREELS results indicate that there are only weak electronic interactions at the Pt/ZnO(0001) interface, while charge transfer and Schottky barrier formation occurs at the Pt/ZnO(0001) interface.
Epitaxial Growth and Characterization of Lattice-Matched MgO/Cr0.7Mo0.3/MgO(001) Layered Structures
Authors: Chambers S.A. , Liang Y. , Gao Y. 
Published: April 2011

AbstractWe have grown by molecular beam epitaxy (MBE) structurally coherent layers of MgO and a random bcc alloy of 70% Cr and 30% Mo to which MgO is lattice matched. Specimens werecharacterized by means of reflection high-energy electron diffraction (RHEED), x-ray photoelectron spectroscopy and diffraction (XPS/XPD), transmission electron microscopy (TEM), and atomic force microscopy (AFM). These systems exhibit excellent long- and shortrange crystallographic order, as well as nearly perfect structural coherence across the interface.
A Study of the MBE Growth of MGO on The FE(001) Surface
Authors: Vassent J.L. , Dynna M. , Patrat G. , Gilles B. , Marty A. 
Published: April 2011

AbstractThe deposition of MgO on the Fe(001) surface has been carried out using electron beam evaporation. MgO is observed to grow epitaxially with a 45° rotation between the Fe(001) and MgO(001) unit cell axes. Oscillations in the intensity of the RHEED specular beam are observed at room temperature showing that growth is two-dimensional. The relaxation of the in-plane lattice parameter during the growth at room temperature has been investigated in-situ by measuring the position of the RHEED streaks and ex-situ with GIXD experiments. Pseudomorphic growth is observed up to about five monolayers. Then the in-plane lattice parameter starts to evolve towards the MgO bulk parameter. HREM shows that the relaxation of MgO occurs via the generation of 1/2<011> misfit dislocations which are non-uniformly spaced at the Fe/MgO interface.
Interfacial Electronic Structure and Full Spectral Hamaker Constants of Si3N4 Intergranular Films from VUV and Sr-Veel Spectroscopy
Authors: French R. H. , Scheu C. , Duscher G. , Müllejans H. , Hoffmann M. J. , Cannon R. M. 
Published: April 2011

AbstractThe interfacial electronic structure, presented as the interband transition strength Jcv(ω) of the interatomic bonds, can be determined by Kramers Kronig (KK) analysis of vacuum ultraviolet (VUV) reflectance or spatially resolved valence electron energy loss (SR-VEEL) spectra. For the wetted interfaces in Si3N4, equilibrium thin glass films are formed whose thickness is determined by a force balance between attractive and repulsive force terms. KK analysis of Jcv(ω) to yield ξ(ξ) for the phases present, permits the direct calculation of the configuration-dependent Hamaker constants for the attractive vdW forces from the interfacial electronic structure.Interband transition strengths and full spectral Hamaker constants for Si3N4 samples containing a SiYA1ON glass have been determined using SR-VEELS from grains and grain boundaries and compared with results from bulk VUV spectroscopy on separate samples of glass and nitride. The At2, Hamaker constant for Si3N4 with glass of the bulk composition is 8 zJ (zJ = 10−21 J) from the more established optical method. The EELS method permits the determination of vdW forces based upon actual local compositions and structure, which may differ noticeably from bulk standards. Current results show that full spectral Hamaker constants determined from VUV and SR-VEEL measurements of uniform bulk samples agree, but care must be taken in the single scattering and zero loss subtraction corrections, and more work is ongoing in this area. Still the results show that for the grain boundary films present in these polycrystalline Si3N4 samples the glass composition is of lower index of refraction. This can arise from increased oxygen content in the intergranular glass and leads to an increased value of the Hamaker constant (24 zJ) determined in situ from the SR-VEELS of a particular grain boundary film.
Sreels Analysis of Oxygen-Rich Inversion Domain Boundaries in Aluminum Nitride
Authors: Bruley J. , Westwood A.D. , Youngman R. A. , Zhao J.-C. , Notis M.R. 
Published: April 2011

AbstractSpatially resolved electron energy loss spectroscopy analysis has been conducted on planar inversion domain boundaries in aluminum nitride. The defects were found to contain 1.5 monolayers of oxygen, in agreement with the most recent structural model of Westwood. From variations in near-edge structure, the local atomic environments of both oxygen and aluminum are compared with α-A1203, γ-A1203 and γ-AION standards. Based upon this study the stnrcture of the inversion domain boundary is found to resemble that of the cubic γ-AION spinel, and eliminates from consideration those structural models based upon ai-Al203. Furthermore, quantification of the shape resonances provided Al-O bond-length data from the inversion domain boundary interface. These distances closely agree with the Youngman Model that has recently been further refined by Westwood et al.
The “Solidification” of Grain Boundaries with Increasing Temperature
Authors: Lojkowski Witold , Palosz Bogdan 
Published: April 2011

AbstractThe aim of the paper is to explain the recently observed de-wetting grain boundary transition with increasing temperature. On the example of a bicrystal from the Fe-6at.%Si alloy, it was found recently that as temperature is increased, the following GB transitions take place: “solid” (or regular) GB-→“premelted” GB →“solid” GB. At the same time the wetting/de-wetting transitions have taken place. Another example of such GB behavior was discovered during sintering of alumina. The inverse melting behavior is explained as follows: low melting point impurities cause GB premelting at low temperatures, However de-segregation of impurities at high temperatures causes return of the GB structure to its regular “solid” state.
Theory of the Physical Properties of Si Nanocrystals
Authors: Lannoo M. , Delerue C. , Allan G. , Martin E. 
Published: April 2011

ABSTRACTThis paper reviews calculations concerning several aspects of silicon crystallites and their relevance for porous silicon. This begins with the optical properties of perfect crystallites: gap versus size, radiative recombination time, relative importance of phonon assisted transitions. A second part is devoted to the determination of the excitonic exchange splitting and of the Stokes shift which are found to bring a similar contribution (∼10 to 20 meV). The effect of surface defects like dangling bonds is then investigated with their contribution to the recombination time. The Auger non radiative recombination time is also calculated and found to be short (∼1 nsec). This is confirmed by some experiments on porous silicon which show a saturation effect of the photoluminescence under intense optical excitation or under cathodic polarization in aqueous solution, Auger recombination preventing the existence of more than one electron-hole pair per crystallite. Donor and acceptor impurities are studied in detail (screening of Coulomb potential, notion of ionization energy) with the conclusion that they are ionized. A final discussion shows the present level of understanding and identifies problems remaining to be solved.
Compound Semiconductor Nanocrystals formed by Sequential Ion Implantation
Authors: White C. W. , Budai J. D. , Zhu J. G. , Withrow S. P. , Zuhr R. A. , Chen Y. , Hembree D. M. , Magruder R. H. , Henderson D. O. 
Published: April 2011

ABSTRACTIon implantation and thermal processing have been used to synthesize compound semiconductor nanocrystals (SiGe, GaAs, and CdSe) in both SiO2 and (0001) Al2O3. Equal doses of each constituent are implanted sequentially at energies chosen to give an overlap of the profiles. Subsequent annealing results in precipitation and the formation of compound nanocrystals. In SiO2 substrates, nanocrystals are nearly spherical and randomly oriented. In Al2O3, nanocrystals exhibit strong orientation both in-plane and along the surface normal.