bluuebunny/crossref_metadata_2025 huggingface dataset:
Monte Carlo Modeling of Atomic Oxygen Interaction with Protected Polymers for Projection of Materials Durability in Low Earth Orbit
Authors: Banks Bruce A. , Auer Bruce M. , Rutledge Sharon K. , Gebauer Linda , Sechkar Edward A.
Published: March 2011

Atomic oxygen in low Earth orbit (LEO) readily attacks and oxidizes exposed spacecraft polymeric materials such as polyimide Kapton photovoltaic array blankets. The application of thin film silicon dioxide protective coatings can greatly extend the useful life of such materials in LEO. A Monte Carlo computational model has been developed which simulates atomic oxygen interaction with polymeric and protective coating materials for both ground laboratory and in-space experiments, allowing the determination of the geometrical shape of atomic oxygen attack of protected polymeric materials at defect sites in protective coatings. Modeling of attack of unprotected carbon-carbon composite materials predicts textured surfaces suitable for high emittance radiators. Results for fiberglass composites indicate loss of the matrix polymer leading to friable fibers. The computational modeling to project in-space performance based on ground laboratory testing predicts mass loss per fluence in space to be approximately one third that observed in plasma ashers.
Thermodynamic and Elastic Properties of Polyethylene at Elevated Temperatures
Authors: Cagin Tahir , Karasawa Naoki , Dasgupta Siddhart , Goddard William A.
Published: March 2011

Over the years molecular modeling techniques, such as Molecular Mechanics, Monte Carlo and Molecular Dynamics have been applied to study the equilibrium thermodynamic and mechanical properties of materials. The accuracy of the predictions made by these techniques strongly depend on the force fields employed to represent the interactions in the studied system. Recently developed force field parameters for crystalline polyethylene are shown to reproduce the mechanical properties of polyethylene accurately through molecular mechanics. Here, we will present the statistical fluctuation formulae for the elevated temperature equilibrium thermodynamic and elastic properties in terms of microscopic variables such as energy, enthalpy, pressure, volume, microscopic strain or stress tensors and present preliminary results of our calculations.
Computersimulations of the Dielectric Breakdown in Ceramics Based on Laplace'S Equation
Authors: Köller Ralf J.
Published: March 2011

In this work, the benefits of a modern personal computer are used to get a deeper insight into the processes occurring in a ceramic material just before and during a dielectric breakdown. Especially, a model to simulate the thermal breakdown behavior in a two-phase material is presented, which is based on a random resistor network. To study the influence of different parameters on the thermal breakdown, simulations were done changing the values of a set of six variables, e.g. external voltage, resistivity, etc. The resulting plots time vs. maximum temperature are shown.
ESR Study of Fluorine Implanted a-Si:H and a-C:H Thin Films
Authors: Wong S. P. , Peng Shaoqi , Ke Ning , Li Pengxu
Published: March 2011

The study of ESR splitting effects induced by fluorine implantation into a-Si:H and a-C:H films has been performed. The implanted fluorine concentration Cp ranges from 1 × 1017 to 6 × 1021 cm−3. It is found that for both a-Si:H and a-C:H after fluorine implantation, in addition to the g1 resonances due to dangling bonds in the respective materials, there is a g2 resonance of g value close to 2.003 in both materials. This g2 resonance is further observed to be closely related to some doping effect of the implanted fluorine atoms in both materials. For a-C:H, it is also found that there is anisotropie hyperflne splitting (HFS) induced by the implanted fluorine atoms. These HFS signals exhibit unexpected peculiar CF dependence and do not show up at some intermediate CF values. A model based on the spin polarization effect has been proposed to attribute the HFS signals to be arisen from interaction between the π electrons of the carbon atoms and the 2p orbitals of the fluorine atoms.
Reduction of Secondary Defects in High Energy O-Implanted Si by High Energy Si Irradiation
Authors: Ellingboe S. L. , Ridgway M. C.
Published: March 2011

The effect of 4.2 MeV, low dose Si irradiation before annealing of 1 MeV, high dose O-implanted Si has been studied. Si irradiation results in differences in the defect structure both before and after high temperature annealing. With no Si irradiation, annealing results in polycrystalline Si (polySi) formation and microtwinning at the front SiO2/Si interface. With Si irradiation, the polySi volume fraction is greatly reduced after annealing, twinned Si having grown in its place. Si irradiation has no effect on Si inclusions within the SiO2 layer. The dependence of secondary defect formation on Si dose and implant temperature is presented. In particular, Si irradiation at low implant temperatures (150°C) and moderate doses (5×1016 cm−2) is shown to be most effective in the reduction of the polySi volume fraction at the front SiO2/Si interface.
Electronic Stopping of Channeled Ions in Silicon
Authors: Hobler Gerhard , Pötzl Hans W.
Published: March 2011

Concentration profiles of channeling and random implants of boron, phosphorus, and arsenic in silicon are compiled from the literature and are analyzed using Monte Carlo simulations. An empirical 3-parameter model of the electronic stopping power is found which yields excellent results for all channeling directions in the energy range of about 20 keV to 1 MeV. The model contains a local impact parameter dependent part and a nonlocal part, the latter increasing with ion energy. In addition, local electron density dependent stopping power models are investigated, using a realistic electron density distribution obtained by first principles band structure calculations. These models fail to describe the slowing down of ions channeled along the <110> axis.
Structural Phase Transition in Buried CoSi2 Layers
Authors: Spanninga W. G. , Sandy A. R. , Niesen L.
Published: March 2011

Heteroepitaxial Si/CoSi2/Si<111> structures were made by high dose implantation of Co in a Si wafer. These single crystaline layers were investigated with 57Co source Mössbauer spectroscopy, 4He ion channeling and X-ray scattering. All results show there is a structural phase transition in the buried CoSi2 layer at a temperature around 200 K.
Lattice Location of Supersaturated Arsenic Atoms in Silicon Studied by Channeled Ion Beam
Authors: Xu Li , Tsien Peihsin , Li Zhijian
Published: March 2011

By using rapid thermal annealing (RTA) we can obtain a me testable carrier concentration which well exceeds the solid solubility of arsenic dopant in silicon. The deactivation of such the supersaturated dopant, however, may result in relaxation of the metastable concentration. This paper describes lattice location of the deactivated arsenic atoms determined by channeling angular distribution. On the basis of the results for lattice site location the deactivation mechanism of supersaturated As in Si is discussed.
Thin Ni Silicide Formation by Low Temperature-Induced Metal Atom Reaction with Ion Implanted Amorphous Silicon
Authors: Erokhin Yu.N. , Patnaik B. K. , Pramanick S. , Hong F. , White C. W. , Rozgonyi G. A.
Published: March 2011

We have extended our recent work [1,2] on buried suicide formation by Ni diffusion into a buried amorphous silicon layer to the case where silicide formation is at lower temperatures on silicon substrates which have been preamorphized. The reaction of metal atoms from a 12 nm Ni film evaporated on top of a 65 nm thick surface amorphous layer formed by 35 keV Si+ ion implantation has been investigated at temperature ≤400 °C. Rutherford Backscattering Spectrometry (RBS) with channeling, cross-sectional transmission electron microscopy (XTEM), X-ray diffraction and four-point-probe measurements were used to determine the structure, interfacial morphology, composition and resistivity of the silicide films. It has been found that an increased rate of silicidation occurs for amorphous silicon with respect to crystalline areas permitting a selective control of the silicon area to be contacted during silicide growth. Vacuum furnace annealing at 360 °C for 8 hours followed by an additional step at 400 °C for one hour produces a continuos NiSi2 layer with a resistivity 44 μΩ cm.
Defect-Minimized SiGe Layer Using Ion Beam Synthesis
Authors: Im Seongil , Washbum Jack , Gronsky Ronald , Cheung Nathan W. , Yu Kin Man
Published: March 2011

Ion Beam Synthesis for SiGe layers was performed to study the end-of-range(EOR) defects and strain-induced dislocations. High Ge doses of 5×1016/cm2, 3×1016/cm2 and 2×1016/cm2 at 120 keV were implanted to obtain 12 at%, 7 at% and 5 at% of Ge peak concentrations respectively. RBS spectra show a projected range(Rp) at a depth of 65nm and an amorphous thickness of 170nm on a wafer with 12 at% of Ge peak concentration. Ge ion implantation was performed both at room temperature(RT) and at liquid nitrogen temperature(LNT), in order to investigate the effect of implantation temperature on reducing EOR defect density. Solid phase epitaxial(SPE) annealing for all SiGe layers was done in nitrogen ambient at 800°C. The EOR defect density is considerably reduced by LNT implantation and the strain-induced dislocations have a threshold Ge peak concentration(about 6 at%) for their abrupt generation. For SiGe layer with 12 at% Ge peak concentration, the amorphous-crystalline(a/c) interfacial morphology changes from a planar interface into a faceted interface during SPE growth at 550°C.
Evaluation of Subsurface Ion Implant Damage by Photothermal Displacement Measurement
Authors: Takamatsu Hiroyuki , Sumie Singo , Nishimoto Yoshiro , Tsunaki Hidetoshi , Nishine Koichi , Hara Tohru
Published: March 2011

Subsurface damage in silicon formed by ion implantation and the residual damage after annealing have been successfully evaluated by measuring the photo-acoustic displacement (PAD) induced by an intensity modulated pump beam. The PAD was detected by a laser interferometrie probe with a sensitivity of 0.1 picometers in a noncontact manner. A temperature rise within the subsurface damage due to a decrease in the thermal conductivity leads to significant thermal expansion and causes a displacement on the sample surface. Therefore, subsurface damage can be monitored by measuring the PAD. Experimental results for As+ and B+ implanted samples indicate that recrystallization of ion implant damage by annealing can be monitored by this technique. Samples of higher doses (>1014/cm2) have residual damage even after annealing at 800'C for 30 minutes. The results for high-energy (2MeV) implanted samples also show that the secondary defects after annealing, which are formed in a deep region a few microns under the surface, can be detected with high sensitivity.
MeV Ion Implantation of Er into LiNbO3
Authors: Fleuster M. , Buchal Ch. , Holzbrecher H. , Breuer U. , Dinand M. , Suche H. , Brinkmann R. , Sohler W.
Published: March 2011

The incorporation of Er into LiNbO3 is of great interest for fabricating waveguide lasers and amplifiers. We compare Er diffusion data with the results of Er implantation, performed at 3.6 MeV energy. Even after annealing for 4h at 1060°C, the resulting Er profiles display very good matching to the optical modes. The results of a theoretical gain estimate are presented.
Colloid Formation in Implanted Glasses
Authors: Arnold G. W. , Mazzoldi P. , Tramontin L. , Boscolo-Boscoletto A. , Battaglin G.
Published: March 2011

Metal colloids in glasses can yield an enhanced (χ((3)) susceptibility which leads to an intensity dependent refractive index. Ion implantation is a convenient means of introducing the metal species. The host glass plays an important role in colloid formation. We have characterized Ag-colloid formation in various silicate glasses and, in addition, have studied the formation of colloids in Ag-doped phosphate glass as a function of N and H implantation. Some preliminary results for Cu-implanted glasses are presented.
Plasma Immersion ion Implantation of Semiconductors
Authors: Cheung N. W. , En W. , Jones E. , Yu C.
Published: March 2011

This paper reviews recent developments of plasma immersion ion implantation (PHI) for semiconductor applications: ultra-shallow junction formation, microscopic conformai doping, metallization, and impurities gettering. We also discuss semiconductor processing issues with PHI: reactor design, wafer charging, surface deposition/etching., and secondary electron emission.
Raman Spectroscopy of C-Irradiated Graphite
Authors: Hembree D. M. , Pedraza D. F. , Romanoski G. R. , Withrow S. P. , Annis B. K.
Published: March 2011

Highly oriented pyrolytic graphite samples were irradiated with C+ ions at 35 keV in a direction normal to the basal plane and subsequently annealed up to 1373 K. Substantial surface topography changes were observed at fluences of 5×1018 ions/m2 and higher using scanning electron and atomic force microscopies. Intricate networks of surface cracks and ridges developed after high dose implantation. A systematic study of the irradiation effects was conducted using Raman spectroscopy. Microstructural changes in irradiated regions were first detected at a dose of 1×1017 ions/m2 through the appearance of the Raman D-line at ∼1360 cm−1. The intensity of this line increases while that of the Raman G-line at 1580 cm−1 decreases as the irradiation dose is increased or the irradiation temperature is decreased. After irradiation at 280K to a fluence of 5×1019 ions/m2 or higher the first order spectrum exhibits one single line at a wavelength intermediate between the D- and G-lines. Damage recovery upon thermal annealing depends not only on the initial damage state but also on the annealing temperature sequence. Samples irradiated to a damage level where two distinct Raman peaks are no longer resolvable exhibited upon direct annealing at a high temperature two distinct Raman lines. By contrast, pre-annealing these highly irradiated specimens at lower temperatures produced less pronounced changes in the Raman spectra. Pre-annealing appears to stabilize damage structures that are more resistant to high-temperature annealing than those induced by irradiation.
The Effect of High Energy Electron Beam on the Interaction Between CH4/CF4 and the Diamond (100) Surface
Authors: Lin B. Y. , Beetz C. P. , Brown D. W. , Lincoln B. A.
Published: March 2011

The interaction of the diamond (100) surface with pure CH4 and CF4 gases was investigated as a function of temperature and total gas exposure. We found that sp2 carbon does not form on the diamond (100) surface after exposures of up to lO9L of CH4 or 106 L of CF4 in a UHV system over the range of temperatures from room temperature to 900°C. When a high energy electron beam (5keV) intersected the path of the impinging gas or the diamond surface was exposed to a high energy electron beam before gas exposures, sp2 carbon was not produced at levels detectable by Auger spectroscopy. However, sp2 carbon was formed when the gas exposure was coincident with the electron beam on the diamond surface. The mechanisms responsible for these observations are discussed.
Molecular Dynamics Simulation of Radiation-Induced Amorphization of the Ordered Compound NiZr2
Authors: Devanathan R. , Lami N. Q. , Okamoto P. R. , Meshii M.
Published: March 2011

We have studied the electron irradiation-induced amorphization of the ordered intermetallic compound NizR2 by molecular dynamics simulations in conjunction with embedded-atom potentials. Randomly chosen Frenkel pairs and chemical disorder were introduced into the system in separate processes. In both cases, the energy and volume of the system rose above the corresponding levels of a quenched liquid and the calculated diffraction patterns indicated the occurence of a crystalline-to-amorphous transition. In addition, the average shear elastic constant fell to about 50% of its value in the perfect crystal and the system became elastically isotropie. These results indicate that NiZr2 can be amorphized by chemical disorder as well as Frenkel pairs and are in good agreement with experimental observations.
Ion Beam Induced Crystallization of Amorphous Si from NiSi2 Precipitates: An In Situ Study
Authors: Fortuna F. , Ruault M. -O. , Bernas H. , Gu H. , Colliex C.
Published: March 2011

By first growing NiSi2 precipitates in a-Si and then irradiating with a 150 keV Si beam, we have studied ion beam induced epitaxial crystallization (IBIEC) of Si initiated at a-Si/NiSi2 precipitate interfaces. The growth shape and its temperature dependence are studied in-beam via in situ transmission electron microscopy. Interface roughening is evidenced. Preliminary results for the Co-Si system are also reported.
Low Energy Fluoroboron Ion Beam Interaction with Silicon Single Crystals
Authors: Huang L. J. , Lau W. M. , Mitchell I. V. , Lee S.-T.
Published: March 2011

Fluoroboron (BF2+) ion implantation into silicon is frequently used for fabrication of shallow junctions. For scaling down of the junction dimensions, one of the efficient approaches is to lower the implantation energy. This work reports fluoroboron ion interactions with (100) oriented silicon at 10 to 500 eV ion energy. Ion bombardment was carried out using a mass-separated BF2+ ion beam in an ultrahigh vacuum low energy ion beam system. The temperature of the silicon crystal during bombardment was kept either at room temperature or 500°C. The reactions (both etching and incorporation) were characterized by x-ray photoemission spectroscopy (XPS), Rutherford backscattering (RBS) and Raman scattering. The results show that BF2+ ions dissociated on the silicon surface at an energy as low as 10 eV and most of fluorine segregated to the surface and desorbed. Both the physical and chemical etching rate of the beam were energy dependent but much lower than the accumulation rate. For beam fluences higher than 1 × 1018/cm2, continuous amorphous boron films were deposited on silicon.
Photo-Assisted Chemical Beam Epitaxy of II-VI Semiconductors
Authors: Ho E. , Coronado G. A. , Kolodziejski L. A.
Published: March 2011

Photo-assisted epitaxy is a versatile growth technique which allows in situ modification of surface chemical reactions. Under appropriate growth conditions the surface stoichiometry can be tuned by selectively desorbing surface species, or by decomposing particular molecular species, or by affecting the reaction rate constant of a chemical process. A potential application of laser-assisted growth rate enhancement or growth rate retardation is in the area of maskless selective area epitaxy. We have investigated the effect of photons on the growth of ZnSe by solid and gaseous source molecular beam epitaxy using various combination of sources. Significant growth rate enhancement (up to 20x), as well as growth rate suppression (as much as 70%), have been observed depending on the sources employed. In all cases, the laser power density remained low (∼200 mW/cm2), and the creation of photo-generated carriers was found to be required. An electron beam incident to the surface has a similar effect and increased the growth rate.
i-CxSiyOzHw Films Formed by Ion Beam Assisted Deposition
Authors: Fountzoulas C. G. , Demaree J. D. , Kosik W. E. , Franzen W. , Croft W. , Hirvonen J. K.
Published: March 2011

i-CxSiyOzHw films were formed by thermal evaporation of a tetraphenyl-tetramethyl-trisiloxane diffusion pump oil onto silicon and steel substrates with simultaneous bombardment of the growing film with 40 keV Ar+ ions to decompose the (C6H5)4(CH3)4Si3O2 molecules. Both the current density of the ion beam and the oil arrival rate were varied to produce hard, adhesive films on room temperature substrates, with densities ranging from 1.4 to 2.3 g/cm3 and Knoop microhardness values (at 15 g load) from 1000 to 2100. Unlubricated friction coefficients against a 440C steel ball with a 50 g load ranged from 0.03 to 0.40, depending on deposition conditions, and all films were more wear-resistant than the substrate materials. The films were examined with RBS, hydrogen forward recoil scattering, SEM, TEM, photon tunneling microscopy, electron diffraction, and ellipsometry to ascertain and correlate their chemical compositions and microstructures with their mechanical/chemical properties (microhardness, adhesion, friction and wear).
Ion and Electron Beam Processing of Condensed Molecular Solids to Form Thin Films
Authors: Ruckman M. W. , Mowlem J. K. , Moore J. F. , Strongin D. R. , Strongin M.
Published: March 2011

Electron and ion beams can be used to deposit thin films and etch surfaces using gas phase precursors. However, the generation of undesirable gas phase products and the diffusion of the reactive species beyond the region irradiated by the electron or ion beam can limit selectivity. Tn this paper, the feasibility of processing condensed precursors such as diborane, tri-methyl aluminum, ammonia and water at 78 K with low energy (100–1000 eV) electron and ion beams (Ar+, N2+ and H2+) ranging in current density from 50 nA to several μ a per cm2 is examined. It was found that boron, boron nitride and stoichiometric aluminum oxide films could be deposited from the condensed volatile species using charged particle beams and some of the physical and chemical aspects and limitations of this new technique are discussed.
Structural Change of Graphite During Electron Irradiation
Authors: Koike J. , Pedraza D. F.
Published: March 2011

Highly oriented pyrolytic graphite was irradiated at room temperature with 300-keV electrons. High resolution transmission electron microscopy and electron energy loss spectroscopy were employed to study the structure of electron-irradiated graphite. All the results obtained here consistently indicated die absence of long-range order periodicity in the basal plane and the loose retention of the c-axis periodicity. The structure was modeled based on a mixture of sixfold and non-sixfold atom rings. The formation of non-sixfold atom rings was related to the observed buckling and discontinuity of the original graphite basal plane.
Synthesis of Ti2N-TiSi2 Layers by One-Step Excimer Laser Irradiation
Authors: Majni Giuseppe , Mengucci P. , Barucca G. , Leggieri G. , Luches A.
Published: March 2011

In the present work a novel approach to suicide and nitride formation on the surface of silicon single crystals wafers is reported. The compound growth occurs directly in the place of interest as a result of a laser promoted chemical reaction. Results indicate that it is possible to obtain a titanium nitride layer superimposed on a titanium suicide film with a single-step laser irradiation process. The thickness of the suicide and nitride layers can be adjusted by a proper choice of the laser fluence and number of subsequent pulses.
Ultrafast Laser Superheating of Metal Surfaces
Authors: Elsayed H. E. , Herman J. W. , Murphy E. A.
Published: March 2011

Reflection high-energy electron diffraction with ∼200-ps temporal resolution is used to study the structural dynamics of the closed-packed surfaces of single crystals of lead and bismuth subjected to ultrafast laser heating. By monitoring the temporal evolution of the diffraction streak intensity, information is obtained on the mean-square vibrational amplitude of the surface atoms and the structural integrity of the surface. Pb(lll) is observed to superheat by ∼120 k above the bulk melting point. With increased heating laser intensity, melting is observed to occur subsequent to superheating. Superheating of Bi(0001) by ∼85 K was also observed.
Laser Heating of Substrate by Multi-Beam Irradiation
Authors: Lu Y. F.
Published: March 2011

A general model is derived for computing the temperature profile induced by multi-beam laser irradiation in a semi-infinite substrate. The model is then applied to calculate 2-beam irradiation induced temperature rise in substrate. From this model, it is possibLe to calculate the temperature profile induced by multi-beam irradiation in substrate. The calculated results show that the double-Gaussian beam has advantages of narrow temperature profile and low heat flow intensity. Flatly-topped temperature profiles can be obtained by converting the Gaussian laser beam.
Interaction Between Intense Nd:Yag Laser Pulse and a Metal
Authors: Ito Yoshiro , Kametani Michiko , Imai Jun-Ichi , Nakamura Susumu
Published: March 2011

Energy absorption of intense Nd:YAG laser pulse at the surface of aluminum was measured as a function of laser energy fluence φ by pbotoacoustic method using a piezoelectric transducer. Luminescence spectra from laser induced plume were measured. A Q-switched Nd:YAG laser which generate pulses of 8 ns duration was used.

Pbotoacoustic signal intensity I increased according to the laser pulse energy at low fluences. At a constant pulse energy, the I was a function of the energy fluence φ and had a threshold φth, When the φ was lower than the φth, the I was constant and corresponded to the absorption coefficient of the metal. Above the φth, it approached the maximum I/max and then began to decrease with further increase in the φ. If we represent the relative change in I at different pulse energies as the normalized intensity I/Imax. a universal curve was obtained.

Below the φth, the process was normal photon absorption by the metal. Damage left on the irradiated surface became evident above the φth, Above the φth and below the Imax. surface temperature increased high enough to form melt and the photo-absorption coefficient would increase during one laser pulse. A shock wave would be formed at the surface and contribute to the increase of the I. Higher φ than at the Imax some processes which inhibit the energy absorption would occur and the I decreased.
Ion Bombardment Effect on the Hardness of Ti(C,N,O) Films Prepared by Ion Beam Controlled Deposition (IBCD)
Authors: Youshan Chen , Yilin Sun , Fumin Zhang , Haichuan Mou , Wei Tao , Shichang Zou
Published: March 2011

Ion beam controlled deposition (IBCD) or ion beam assisted deposition (IB AD) of Ti(C,N,O) films has been investigated much in the last decade for both the advantage of this advanced technology and the promising properties of such materials. Ti(C,N,O) films are various solid solutions of interstitial compounds TiC, TiN and TiO of F.C.C structure with lattice constants lying between the values of the pure compounds. Some content of oxygen improves their wear resistance due to the lower fn;e enthalpies of such films in comparison with pure TiC and TiN films [1]. Many so-synthesizcd titanium carbide and titanium nitride films reported in published papers were actually of this sort as they often had more or less oxygen content from residual gas in vacuum. A number of papers were contributed to depict the texture and composition dependence of film on the arrival ratio of assisting ions versus deposited atoms (AR) as well as their mechanical properties [2–6]. However, the film formation mechanism in IBCD isn't quite clear yet, especially for cases with assisting ion energy of several to tens of keV. During a course to synthesize Ti(C,N,O) films by IBCD with the two beam technique, datum were accumulated. Based on a part of it, a previous paper on ion beam governed preferential growth in IBCD has been published [7]. This paper was aimed to search for the origin of ion bombardment effect on film hardness.
Neutral Beam Source Design and Beam Kinetic Energy Activated SiO2 Etching
Authors: Chen Lee , Sekiguchi Akihisa , Podlesnik Dragan
Published: March 2011

An unique method is used to produce a low energy nonthermalized fast neutral radical beam wliich can activate the SiO2 surface for chemical reaction at the desired incident energy. The fast neutral beam energy is continuously adjustable (2eV<Ek<200eV) and the beam flux is typically 5×1015cm−2 sec−1(∼4L). An uniform large diameter plasma is also made for the production of neutral beam covering 5”wafer and larger. Large diameter neutral beam single wafer reactor is feasible with off-the-shelf pumping technology.
Effects of Additive Gas on SiO2 Etching
Authors: Miyakawa Yasuhiro , Hashimoto Jun , Ikegami Naokatsu , Kanamori Jun
Published: March 2011

Precise control of critical dimension(CD) loss (defined as the length of the top of contact hole minus the bottom of resist in this paper) and etched profile of contact holes is a key technology in the fabrication of Ultra Large Scaled Integrated Circuit(ULSI). In case of fine contact hole etching, small CD loss and vertical profile is essential. We have found out that N2 addition to Ar/CHF3/CF4 sharpens etched profile with CD loss kept small. And N2 addition also increases etch rate without a heavy deterioration of selectivity of SiO2 versus heavily doped n-type poly cry stall ine Si(n+ poly Si). Mechanisms of changes in etching characteristics have been investigated and discussed with the emphasis on adlayer formed on etched surface.
Sub-Micron Mesotaxial CoSi2 Wires
Authors: Liddle J. Alex , Zimmerman Neil M. , White Alice E. , Short Ken T. , Fetter Linus
Published: March 2011

Transition metal suicides are receiving an increasing amount of attention as materials for VLSI interconnects because of their low resistivities and ease of integration with silicon. A recently invented technique, mesotaxy, allows the production of buried single-crystal suicide layers in silicon.

Buried suicide layers made by implantation into (100) Si wafers can be patterned by restricting the implant with an oxide mask, giving great flexibility in the types of features that can be produced. We have fabricated simple microstructures to investigate the formation and properties of mesotaxial CoSi2. Wires of constant dose but varying widths exhibit a transition in morphology from {111} faceted wires to largely (100) faceted layers. After annealing for prolonged periods, the finer wires show the effects of coarsening. We have also observed the movement of a significant amount of Co from the oxide implant mask into the substrate during these anneals. The wires show greatly improved thermal stability compared to polycrystalline suicides formed by deposition.1
Heat Transfer in Melt Spinning Cooling Belts and Drums
Authors: Swanson B. W. , Williams R. S. , Draper R.
Published: March 2011

Fourier series solutions have been obtained for the temperature distributions in melt spinning cooling belts and drums. These solutions have been used to determine drum and belt designs for producing 0.050 inch steel sheet. This paper discusses thermal design parameters for cooling drums used in melt spinning rapid solidification.
Melt-Spinning a Commercial Aluminium Alloy
Authors: Willis T C , Cantor B
Published: March 2011

A commercial aluminium alloy (3004) has been melt-spun on both an aluminium and a copper substrate. The meltspinning conditions have been varied in order to determine the optimum spinning parameteis for the apparatus used. The resulting ribbon has been examined by optical microscopy, transmission electron microscopy and anodization to show differences in grain structure and second phase distribution between the as-received rolled sheet and the melt-spun ribbon. X-ray diffractometry has been used to obtain information about the different intermetallic phases present in the sheet and ribbon, and peak heights of X-ray diffractometer traces have also been used to indicate textures present in the ribbons spun on aluminium and copper substrates.
Dynamic Compaction of Al Alloys
Authors: Sears J.W. , Muddle B.C. , Fraser H.L.
Published: March 2011

Powders of Al alloy 7091 have been consolidated by means of dynamic compaction. The dependence of density and hardness on projectile velocity has been determined. The resulting as-compacted material has been characterized using analytical transmission electron microscopy and evidence of interparticle melting observed. The microstructural responseof the compacted material to heat treatment at 523 and 723°K has been investigated.
Corrosion Resistance Of fe- and Ni- Based Metallic Glasses
Authors: Reinders B.-O. , Bergmann H. W.
Published: March 2011

The corrosion behaviour in liquid electrolytes were investigated for some Fe- and Ni-based metallic glasses varying pH-value, electrolyte temperature and heat treatment. For some (Fe100-xMx)83B17 glasses the high temperature oxidation behaviour was studied.
Kinetics and Morphology in Rapid Solidification
Authors: Bergmann H. W. , Fritsch H. U.
Published: March 2011

The important parameters in all descriptions of the kinetics of crystallization behaviour are the differences in free energy Δgv between the liquid (glassy) phase and the various stable and metastable crystalline phases. The various quenching techniques can be subdivided into those in which the cooling rate is determined by the heat diffusivity and those in which the heat transfer coefficient is important. The temperature gradient and the solidification rates are different in the two cases. An additional difference is the nucleation rate which is dependent on the degree of undercooling.
High Strength Copper-Nickel Alloys Made by Rapid Solidification Technology (Rst)
Authors: Panchanathan V.
Published: March 2011

Rapid solidification technology (RST) has been shown to offer outstanding prospects of processing new cost-effective engineering materials with superior properties. There has as yet been only limited effort in the use of RST to synthesize new and improved copper-base alloys. A detailed investigation has been carried out to develop new coppernickel alloys by RST. These alloys find extensive use as condenser tubes, seamless tubes, etc.

New alloy systems suitable for processing by RST have been identified. These systems are as follows:

a) Cu-Ni-B

b) Cu-Ni-Al-B

c) Cu-Ni-Cr-B

d) Cu-Ni-Al-Cr-B

The preferred composition ranges and maximum attainable hardness for each system are given. It is of interest to note that the maximum hardness values attained for this system are around 500 Kg/mm2 which is much higher than the hardness of the conventional copper-nickel alloys.
Precipitation Strengthening Of Rapidly Solidified Austenitic Stainless Steels
Authors: Megusar J. , Chaudhry A. , Imeson D. , Grant N. J.
Published: March 2011

Precipitation kinetics was studied in a rapidly solidified 316 stainless steel containing 0.22% C and 1% Ti. A high density of fine TiC particles was obtained by annealing at 923 to 973 K. An increase in recrystallization temperature and room temperature yield strength was observed as compared with the rapidly solidified 316 stainless steel with a nominal carbon and titanium content. An extension of solid solubility by rapid solidification thus offers a potential for developing precipitation strengthened austenitic stainless steels to improve structural and mechanical stability and likely the irradiation resistance.
Metallic Glass Cladding Of High Strength Steel Using Electron Beams
Authors: Mawella K J A , Honeycombe R W K
Published: March 2011

The effects of electron beam surface melting on a high strength Ni-Cr-Mo-V steel are first described with particular reference to the refined microstructure and the increased surface hardness. Similar experiments on an Fe80P13C7 alloy are described, in which surface amorphous layers were produced leading to hardnesses around 910VPN at the surface up to 1250VPN further in and falling to 650VPN in the as-cast crystalline substrate.

Metallic glass cladding of the steel was achieved by coating the steel surface with thin layers of powdered Fe80P13C7 alloy, and traversing with an electron beam sufficient to fuse the powder layer. Process variables including beam power and thickness of powder layer were examined and optimum conditions for glass formation in the surface layer were determined. These layers were examined by optical and electron microscopy, X-ray diffractometry and energy dispersive X-ray analysis. The microhardness variation with distance from the surface was also determined and found to be in the range 880–1150VPN.
New Phenokena in Electron Beam Glazing
Authors: Strutt P. R. , LeMAY J. , Tauqir A.
Published: March 2011

Linear heat source surface melting studies have been carried out using a 1 to 15 kH oscillating beam incident on a steel substrate to produce a 3 to 35mm wide rapidly solidified strip of material at rates ranging from 1 to 100 cm.s−1. A simple relationship betweenmelt depth, power, and substrate velocity (V) has been determined at low values of V; limited results at higher velocities appear to follow the same relationship. A serendipitous discovery was the effect of prior surface homogenization treatment on the geometrical and microstructural uniformity of the subsequently formed rapidly solidified layers. This pre-treatment resulted in the formation of thin layers of uniform thickness under the most rapid processing condition (V = 100 cm.s−l). Omission of pre-treatnent resulted in irregular and sometimes discontinuous surface layers. In the case of a high speed steel of near peritectic composition (M2)pre-treatment resulted in the almost complete elimination of massive austenitic region within the dominant ferrite phase.
Electron Beam Glazing of Hardfacing Alloys
Authors: Kurup M. , Tauqir A. , Strutt P. R. , Kear B. H.
Published: March 2011

Electron beam glazing has been used to reprocess hardfacing deposits of conventional Stellite 6 alloy, and TiC, TiB2 particle strengthened Stellite 6. By varying the scanning mode and power density, a wide variety of microstructures have been developed, with significant increases in hardness. Single-pass line source scanning produces a distribution of moderately sized carbides (2–5μm) in a dendritic matrix, whereas multi-pass processing gives a more homogeneous refined microstructure with submicron carbides. Point source scanning, in contrast, produces the most refined microstructures. Effective control of the carbide distribution, including both fine and coarse carbides, may be the key to tailoring the microstructure for specific wear applications.
Estimation of Surface Diffusion Length from AFM Images of Faceted GaAs(111) Homoepitaxial Films
Authors: Yang K. , Schowalter L. J. , Thundat T. G.
Published: March 2011

GaAs films grown on exact (111) substrates in the reconstruction regime always show facets. We have studied the surfaces of these films with an atomic force microscope. The facets are composed of vicinal surfaces which are tilted by small angles (∼ 2°) from the exact (111) plane. From the geometry of the facet, average displacement of adatoms is calculated. The results indicate that the diffusion length under the growth condition is more than 0.2 μm.
Atomic Force Microscopy of Growth Features on Epitaxial CdHgTe Films
Authors: Aindow M. , Cheng T. T. , Jones I. P. , Astles M. G. , Williams D. J.
Published: March 2011

Atomic Force Microscopy has been used to observe the details of surface morphology on CdxHg1-xTe epitaxial films. On films grown by liquid phase epitaxy (LPE), tiered pyramidal features were observed and these are consistent with enhanced nucleation and growth at emergent edge dislocations which thread through from subgrain boundaries in the substrate. On films grown by metal-organic vapour phase epitaxy (MOVPE) using the interdiffused multilayer process (IMP), terraces and steps are observed as expected but the step edges are decorated. It is suggested that this corresponds to the deposition of one binary layer in Volmer-Weber mode.
Microstructure - Roughness Interelation in Ru/C and Ru/B4C X-RAY Multilayers
Authors: Nguyen Tai D. , Gronsky Ronald , Kortricht Jeffrey B.
Published: March 2011

X-ray specular and non-specular scattering, and high-resolution transmission electron microscopy (HRTEM) were performed to study the evolution of the microstructures and interfacial roughness in Ru/C and RU/B4C multilayers upon annealing. The microstructure of the approximately 1.4 nm thick Ru layers in the as-prepared 3.5 nm period multilayers is predominantly amorphous. The Ru layers in the Ru/B4C multilayer show RuB2nano-crystallites after annealing at 600°C for one hour, while those in the Ru/C multilayer crystallize to form hexagonal Ru crystallites. Cross-sectional HRTEM of the annealed Ru/C multilayer also shows agglomeration of the Ru layers. Non-specular measurements of the Ru/C multilayers indicate an enhanced uncorrelated roughness upon annealing. The diffuse component in the as-prepared and annealed RU/B4C multilayers shows insignificant changes. The increase in interfacial roughness in the Ru/C multilayer results from agglomeration of the Ru after annealing, consistent with HRTEM observation.
Reaction Kinetics of Atomic chlorine on Si(100)2×1
Authors: Karahashi Kazuhiro , Matsuo Jiro , Horiuchi Kei
Published: March 2011

The interaction of atomic chlorine with Si(100)2×1 surfaces was studied by using chlorine atom beams. The etching reaction of silicon substrates has been observed when chlorine atoms impinged on the chlorinated surface, at substrate temperatures below 600°C. The major desorption product is SiCl2. Studies of the temperature dependence of the reaction showed that the activation energy are 0.08 eV at 0.4 ML and 0.2 eV at 0.8 ML. These extremely low activation energies suggest that the surface reaction is mainly driven by the internal energy of incident atomic chlorine instead of thermal excitation from Si(100) solid surface. Therefore chlorine atoms enter the transition state without equilibrating at the surface prior to the reaction. The reaction strongly depends on the chlorine coverage on the surface. The reaction occurred above 0.3 ML. The etching probability of the surface reached a maximum at 0.4 ML, and decreased with increasing coverage.
Interface Roughness: What is it and How is it Measured?
Authors: Chason E. , Falco Charles M. , Ourmazd A. , Schubert E. F. , Slaughter J. M. , Williams R. S.
Published: March 2011

A panel discussion on interface roughness was held at the Fall 1992 Materials Research Society meeting. We present a summary of the results presented by the invited speakers on the application and interpretation of X-ray reflectivity, atomic force microscopy (AFM), scanning tunneling microscopy (STM), photoluminescence and transmission electron microscopy. A transcript of the moderated discussion is provided in the final section.
Interface Roughness Determined by Diffuse Scattering and by Reflectivity of Hard X-Rays
Authors: Lengeler B. , Hüppauff M.
Published: March 2011

X-ray reflectivity and diffuse scattering are powerful techniques for the non-destructive determination of the vertical and lateral roughness of external and internal interfaces. The influence of roughness on the reflected and transmitted amplitudes is treated in terms of a model first described by Névot and Croce. The diffuse scattering is described by an improved distorted wave Born approximation. A few examples will demonstrate the possibilities of the techniques.
Investigation of Roughness at InP/InAs Interfaces
Authors: Brasil M.J.S.P. , Nahory R. E. , Tamargo M. C. , Schwarz S.
Published: March 2011

We have investigated the interface roughness of single thin InP/InAs quantum wells grown by Chemical Beam Epitaxy. We report results of low temperature photoluminescence and secondary ion mass spectroscopy. The interface roughness is characterized by multiple-line photoluminescence spectra and is very sensitive to parameters such as the growth temperature. Details of the interface roughness are discussed based on the shifts of the excitonic energies observed by photoluminescence.
A New Quantitative Roughness Measurement and its Application in the Polysilicon/Silicon Dioxide Interface
Authors: Lin Su-Heng , Hatalis Miltiadis K.
Published: March 2011

A quantitative approach for characterizing the interface roughness between two materials by cross sectional transmission electron microscopy (XTEM) is proposed. This approach is based on obtaining an interface height distribution curve (IHDC). The interface roughness can be characterized quantitatively by extracting from IHDC three parameters: the mean, median and maximum interface height. This new method has been applied in the characterization of the interface between thermally grown silicon dioxide and polycrystalline silicon thin films deposited by low pressure chemical vapor deposition. It is shown that high temperature processing yields an interface that has higher roughness.
Surface Roughness in Kinetic Growth with Diffusion
Authors: Yan Hong
Published: March 2011

The evolution of surface roughness in kinetic growth with diffusion is studied by computer simulation of ballistic deposition with an activated hopping algorithm, in which the deposited particles diffuse on the surface via random walks. The results demonstrate that the KPZ-type scaling dictates the asympototic statistical properties of surface roughness at elevated temperatures, which are consistent with earlier studies. As surface diffusion is crucially dependent on substrate temperature and deposition rate, we show that they play essential roles in determining the morphology of the film.
The Origins of Epitaxial Orientations in thin Films
Authors: Thompson Carl V.
Published: March 2011

When a continuous film is deposited on a planar, single crystal substrate, there is usually a single set of relative film-substrate orientations for which the free energy of the film-substrate interface is minimized. It is often assumed that epitaxial films have adopted the orientation which minimizes this energy. However, this is not necessarily the case. Orientation selection is also constrained by minimization of the energy of the/reesurfaceof a film, as well as by minimization of the strain energy. In systems in which films grow by an island mechanism, epitaxial orientations can be established duringor afternucleation, and can change before orafterformation of a continuous film. Interfacial and surface energy minimization is constrained differently for islands and films. Epitaxial grain growth is a process which occurs in continuous films, in which epitaxially-aligned, energy-minimizing grains grow at the expense of other grains. Recent experiments on epitaxial grain growth in polycrystalline Ag films on single crystal Ni is discussed to illustrate, the affects of surface, interface, and strain energy minimization on epitaxial orientation selection.
Role of Atomic Size and Valence in Bonding and Diffusion at Metal Surfaces
Authors: Feibelman Peter J.
Published: March 2011

First-principles calculations and corresponding experimental results underline the importance of basic chemical concepts in understanding bonding and diffusion of atoms at and on metal surfaces. Examples discussed include the outward relaxation of clean Be(0001), the separation energies of metal-adatom dimers, concerted substitutional self-diffusion on fcc(001) and (110) surfaces, and adsorption and diffusion barrier sites for adatoms near steps.
Substrate Surface Structure Effects on Microstructure of Epitaxial Films
Authors: Guo J. , Chang H.L.M. , Zhang H. , Lam D. J.
Published: March 2011

The microstructure of epitaxial thin films grown on sapphire substrates using the metal organic chemical vapor deposition (MOCVD) technique were found to depend on the substrates surface structure. The epitaxial Ti02 films grown on the sapphire (0001) substrates were highly-oriented poly-crystal and the films on the (1120) substrates were single crystal. First-principles total energy calculations were carried out to gain atomistic understandings of sapphire surface structures and their effects on microstructure of epitaxial films. The surface terminating atom planes were found to be Al atoms for the (0001) surface and O atoms for the (1120). The minimum step heights were found to be one sixth of the lattice constant c for the (0001) and one half of the lattice constant α for the (1120). The steps of the minimum height or its odd multiples on sapphire (0001) surface were shown to double the number of variants in the deposited films. The symmetry and step of the substrate surface and the symmetry of the epitaxial growth plane were found to control the microstructure of the epitaxial films.