bluuebunny/crossref_metadata_2025 huggingface dataset:
Time Resolved Spectra of Raman and Thermal Emission During Pulsed Laser Heating of Silicon
Authors: Von Der Linde D. , Wartmann G. , Kemmler M. , Zhu Zhen-He
Published: March 2011

Laser heating of crystalline silicon is investigated with 10 ns laser pulses at 532 nm Raman spectra below the transition threshold show distinct shifts to low frequencies. The absence of line shifts at higher energy is due to a time resolution artifact. Temperatures evaluated from frequency resolved anti-Stokes/Stokes ratios are in agreement with the temperature estimated from line shifts, and provide clear evidence that the surface reaches the melting point. These conclusions are confirmed by independent measurements of the thermal emission. Time-resolved pyrometry also provides the temperature evolution of the liquid phase.
Stress Effects on Raman Measurements of Pulsed Laser Annealed Silicon
Authors: Jellison G. E. , Wood R. F.
Published: March 2011

It has recently been shown that the front surface region of the silicon lattice is severely strained during pulsed laser irradiation. This uniaxial strain reduces the symmetry of the front surface region, resulting in additional shifts and splittings of the phonon frequency and changes in the Raman scattering tensor. It is shown that, for the case of pulsed laser irradiation, the phonon frequency is increased, and the 3-fold degenerate optical phonon is split into a singlet and a doublet. The changes in the Raman scattering tensor make it non-symmetric, and generally invalidate the technique used by Compaan et al. to determine the cross section experimentally. The complications introduced by the presence of stress during pulsed laser annealing, coupled with the temperature dependence of the optical and Raman tensors, make a simple interpretation of the Stokes to anti-Stokes ratio in terms of lattice temperature extremely unreliable.
Melting Phenomena and Impurity Redistribution During Pulsed Laser Irradiation of Amorphous Silicon Layers
Authors: Narayan J. , White C. W. , Holland O. W.
Published: March 2011

we have investigated microstructural changes and phase transformations in 30Si+, 75As+, 63Cu+, and 115In+ implanted amorphous silicon layers as a function of pulse energy density. Cross-section electron microscopy studies have revealed the formation of two distinct regions, large and fine polycrystalline regions below the threshold for “defect-free” annealing. The fine polycrystalline region is formed primarily by explosive recrystallization, and occasionally by bulk nucleation and growth. The impurity redistribution in the large and fine polycrystalline regions were determined by Rutherford backscatterinq measurements. Large redistributions of impurities in the large poly region are consistent with velocity of solidifications of 3–5 ms−1. The nature of impurity redistributions in the fine poly region as a function of distribution coefficient provides information on the details of liquid phase crystallization phenomena.
Laser Quenching of Amorphous Si from the Melt Containing Dopants
Authors: Campisano S. U. , Jacobson D. C. , Poate J. M. , Cullis A. G. , Chew N. G.
Published: March 2011

The formation of amorphous Si by the quench of a thin surface layer melted by fast UV laser irradiation has been investigated. The starting (111) surface layers were either pure or doped with As, Bi, In and Te by implantation. The asimplanted samples were recrystallized by ruby laser irradiation resulting in surface accumulation of Bi,In and Te. For the same UV irradiation condition, the amorphous layer formed in As, Bi, In or Te doped Si is about twice the thickness of the amorphous layer formed on pure Si. In the presence of the surface accumulation of Bi, In or Te, the amorphization results in an inward segregation of the dopant. For In, a very thin metal layer ˜15Å thick, is formed 150Å beneath the amorphous surface. These results show that the amorphous-liquid interfacial segregation coefficients for Bi, In or Te are less than unity and that the amorphous solidification proceeds from the surface and bottom of the liquid layer.
Short Time annealing of As and B Ion Implanted Si using Tungsten-Halogen Lamps
Authors: Sedgwick T. O. , Kalish R. , Mader S. R. , Shatas S. C.
Published: March 2011

B and As implanted Si wafers have been thermally annealed by an array of tungsten halogen lamps at 1000–1200°C for 1–10 sec. Annealing above 1100°C leaves the crystal free of extended defects in all cases as determined by TEM. An enhanced diffusion is observed above normal values characterized by a low activation energy for both As and B samples. This enhanced diffusion is transient and occurs within about one second since the RBS and SIMS dopant profiles are identical for 1 sec and a 10 sec anneal.
Evening Panel Session (November 16, 1983) Soi Technologies for Integrated Circuits
Authors: Fan John C. C. , Akasaka Y. , Cullen G. W. , Gibbons J. F. , Hill C. , Vail P. J.
Published: March 2011

There are a number of viable approaches to silicon-on-insulator (SOI) technologies, and the panel session has assembled a number of leaders in the SOI community for their views of “SOI Technologies for Integrated Circuits.” Their viewpoints, shown in tabulated form, were presented for general discussion in the session which was attended by about 150 people. Although SOI technologies are useful for many applications, most of the panelists agreed that the most appropriate near-term applications are for high-speed, high-density integrated circuits. Various SOI technologies, including silicon-on-sapphire (SOS), are currently in the running, but the majority of the panelists felt that for SOI technologies to be widely adopted, SOI must be available as a proven manufactured product within two to three years.
Ultrafast UV-Laser Induced Oxidation of Silicon
Authors: Orlowski T.E. , Richter H.
Published: March 2011

A new low temperature method of forming high quality patterned silicon dioxide (SiO2) layers up to a thickness of 1 μm on silicon substrates is presented. UV pulsed laser excitation in an oxygen environment is utilized. IR absorption spectroscopy, CV and IV measurements are employed to characterize the oxide films and the Si-SiO2 interface. No shift but a significant broadening of the Si-O stretching mode compared with thermally grown oxides is found indicating that the laser grown oxide is stoichiometric but with a higher degree of disorder. From CV measurements we deduce a fixed oxide charge near the Si-SiO2 interface of 6×1010/cm2 for oxides that have been thermally annealed in O2 following the laser induced growth making this material a candidate for applications in semiconductor devices.
Solid Silicon at the Melting Temperature is Crystalline
Authors: Biegelsen D. K. , Nemanich R. J. , Fennell L. E. , Street R. A.
Published: March 2011

Recently it has been proposed that solid silicon at the melting temperature is amorphous. There is no known case of a solid for which an amorphous structure is the equilibrium state. Silicon thin films on insulating substrates, when heated radiantly, melt inhomogeneously and provide an accessible high temperature system for a study of a solid coexisting with its melt. Using the intensity, energy distribution and polarization of Raman scattering from silicon lamellae, we have proved that the equilibrium phase is in fact crystalline. Furthermore, we give strong evidence that the solid regions have {100} texture at Tm.
Single Crystalline Germanium Island on Silicon Dioxide by Zone Melting
Authors: Takai M. , Tanigawa T. , Gamo K. , Namba S.
Published: March 2011

Single crystalline germanium islands on SiO2 have been formed by zone melting with graphite strip heaters. Two types of geometrical patterns for islands were successfully used to obtain large single crystalline islands. Most germanium islands were found to be single crystal and the predominant orientation was (100). Electron concentrations of 1016 - 1018/cm3 with Hall mobility of 3 × 103 − 1 × 103 cm2 /Vsec were obtained for single crystalline germanium islands. Gallium Arsenide layers, grown by molecular beam epitaxy, on the germanium islands were found to emit photoluminescence, the intensity of which was almost comparable to that of gallium arsenide layers on bulk germanium crystals.
Faceted Melting and Superheating of Crystalline Si Irradiated with Incoherent Light
Authors: Celler G. K. , Jackson K. A. , Trimble L. E. , Robinson McD. , Lischner D. J.
Published: March 2011

We report and analyze the breakup of a crystalline silicon surface into solid and molten faceted segments by radiative heating. Melting starts at discrete sites since there is a nucleation barrier requiring superheating of the surface. Once started, the melt remains localized and does not encompass the entire surface because of the changes in optical properties of Si upon melting. It is estimated that superheating by <0.5 K should be sufficient to stabilize faceted melt regions spaced 200 μm apart. The preliminary measurements, however, indicate superheating by several degrees.
Lateral Solid Phase Epitaxy of Silicon Over Oxide
Authors: Roth J.A. , Olson G.L. , Hess L.D.
Published: March 2011

We review recent progress in the growth of siliconon-insulator films by lateral solid phase epitaxy. The temperature dependence of the rates of random crystallization and solid phase epitaxy are used to predict the maximum growth of Si over oxide achievable by this technique. Actual overgrowth distances of 10 μm obtained in UHV-deposited films are considerably less than the values predicted. Several possible causes of the difference between observed and predicted overgrowth are discussed.
A Model for Cw Laser Recrystallization Including Reflectivity Effects
Authors: Calder I.D.
Published: March 2011

A simple, practical model is developed for cw laser recrystallization of silicon and SOI structures, taking into account spatial variations in optical reflectivity. The power absorption is assumed to be uniform within each of three regions: the central molten spot, the annular two-phase region, and an outer annulus to account for absorption in the solid phase. Analytic expressions are obtained for the radial and depth dependence of the temperature, for the melt depth, the melt radius, the melt threshold, the crystallization threshold and the substrate melt threshold. SOI structures are considered and comparison with some experimental results shows excellent agreement.
Comparison of Soi Technologies
Authors: Wai Lam Hon
Published: March 2011

Silicon-on-Insulator (SOI) technologies are becoming more important as CMOS becomes the preferred technology for VLSI. The progress of the three most actively researched SOI technologies, beam-recrystallized SOI, implanted buried oxide and Full Isolation by Porous Oxidized Silicon will be summarized in this paper.
A Current Conduction Mechanism in Laser Recrystallized Silicon Metal-Oxide-Semiconductor Transistors
Authors: Lee Han-Sheng
Published: March 2011

N-channel MOS transistors were fabricated on silicon films that had been recrystallized by an argon ion laser at different power levels. These transistors showed electrical characteristics similar, but somewhat inferior to those devices fabricated on single crystal silicon substrates. These differences are attributed to the presence of trapping states at the grain boundaries of the crystallites in the recrystallized silicon. A coulombic scattering model is presented to explain these differences. In the case of films annealed at low laser power, an additional factor of nonuniform trap state distribution is invoked to explain device characteristics. This model provides an adequate explanation for the observed transport properties of transistors fabricated from recrystallized silicon films.
Two-Color Picosecond Measurements on Electron-Hole Plasmas Close to the Melting Phase Transition
Authors: Fauchet P.M. , Siegman A.E.
Published: March 2011

We demonstrate a novel technique to study in detail the picosecond dynamics of semiconductors close to the melting phase transition. A variable-energy IR pulse (1.06 μm) is used to melt Si or GaAs samples via free carrierabsorption (FCA) in the dense and hot electron-hole plasma (EHP) produced by a preceding visible (532 nm) pulse. By varying the delay between the pulses and their relative intensities, we are able to verify the Lietoila-Gibbons model for pulsed laser heating, and to measure in detail important parameters of the EHP over a wide range of experimental conditions.
Pulsed Laser Annealing of Zirconia Capped, Native Oxides Free GaAs Surfaces
Authors: Pribat D. , Mercandalli L.M. , Croset M. , Siejka J.
Published: March 2011

We have studied the effects of pulsed laser irradiation on silicon implanted, thermally activated , Calcia Stabilized Zirconia (CSZ) capped GaAs substrates. Reference substrates have also been irradiated in air for comparison. CSZ as a solid electrolyte has been used to chemically reduce the GaAs surface native oxides prior to irradiation while maintaining the surface stoechiometry. Our results indicate a spectacular decrease in defect density after laser irradiation of the CSZ capped-native oxide free samples, as compared to the samples irradiated in air.
Ir Radiation Transient Annealing of Silicon Implanted Si Gallium Arsenide
Authors: Ezis A. , Yeo Y. K. , Park Y. S.
Published: March 2011

The electrical properties of IR radiation transient annealed Si implanted semi-insulating GaAs are presented for 100 keV ion doses from 3 × 1012 to 3 × 1014 cm−2. For wafers implanted with 3 × 1012 cm−2 doses, suitable for FET channel layers, carrier concentration and drift mobility profiles were determined from C-V and transconductance measurements on fat FET structures. Optimum electrical activation and carrier concentration profiles were obtained for peak pulse temperatures of 930–950°C. Van der Pauw measurements were made on substrates implanted with Si doses ≥ 1 × 1013 cm−2 to determine sheet carrier concentration and Hall mobility. The peak pulse temperature required to give optimum activation efficiency is found to increase with dose. The results presented here demonstrate that undoped substrates are preferable to Cr-doped substrates for low dose device applications.
Infrared Measurement of Carrier Density, Lattice Temperature and Melt Depth During Nanosecond Pulsed Laser Annealing of Silicon and Germanium
Authors: Preston J. S. , van Driel H. M. , Sipe J. E.
Published: March 2011

We have performed infrared reflectivity measurements using 5.3 and 10.6μm probes to determine the plasma density, lattice temperature and melting kinetics of silicon and germanium following excitation by 25 nanosecond, 0.53 and 1. 06μm pulses. Below the threshold of melting, the maximum plasma densities are approximately 1020 cm−3; for both materials; these values and the spatial and temporal evolution of the plasma are consistent with well known generaticn, diffusion and recombination processes. Above the threshold for melting we have taken advantage of the large skin depth at infrared wavelengths to determine the melt front kinetics for depths up to 1000 Å using a contactless technique.
Liquid Phase Growth of Epitaxial Ni and Co Silicides by Pulsed Laser Irradiation
Authors: Tung R. T. , Gibson J. M. , Jacobson D. C. , Poate J. M.
Published: March 2011

Epitaxial Ni and Co silicides have been fabricated using pulsed laser melting. Interfacial instabilities and cell formation are suppressed during the liquid-phase epitaxy by melting mono or disilicide layers. Single crystal NiSi2 and CoSi2 films have been grown on (100) and (111) Si following a post-anneal. This method does not require UHV deposition or reaction techniques.
The Influence of Layer Structure on the Synthesis of AlSb by Laser Irradiation of Al/Sb Thin Film Couples
Authors: Baufay Luc , Pigeolet Andre , Andrew Rod
Published: March 2011

We have previously described the formation of thin AlSb films by laser irradiation of sandwich-like structures of the components, and have shown that under quasi-adiabatic conditions, the transformation can be triggered by furnishing sufficient laser energy to just melt a part of the components; subsequent progressive liberation of the heat of formation of the compound drives the reaction to completion. In this paper, we clarify some details of the reaction and we investigate the influence of initial layer structure,thermal history, and total film thickness on the required laser threshold energy.
Ferrimagnetic Behavior and Magnetoresistance of Fe/Gd Double Structured Multilayer Films
Authors: Fujimori H. , Kamiguchi Y. , Hayakawa Y. , Takanashi K.
Published: March 2011

We prepared Fe/Gd double structured multilayer films (DSMLF's). The Fe/Gd DSMLF has a longer period λl, and it is composed of alternate stacking of two types of Fe/Gd submultilayers with a shorter period λs. One type of Fe/Gd submultilayers has dominant Fe layer magnetization, and the other, dominant Gd layer magnetization. λs was varied in the range from 12 to 100Å, keeping λl to about 250Å. The magnetization of Fe/Gd DSMLF's with λs≦36Å shows a spin-flop in magnetic fields lower than 1k0e at room temperature. The compensation temperature Tcomp was found to decrease with increasing λs. Tcomp crosses room temperature at λs=24Å, and then the spinflop field Hsf at room temperature takes a minimum value of the order of a few tens oersteds. Thus, we show that Hsf at room temperature can easily be tuned to a desired value by varying λs. Longitudinal (pl) and transverse (pt) magnetoresistances show a crossover, depending on the angle between directions of the electric current and of the Fe layer magnetization.
Cems Interface Study of (Fe/M)-Multilayers (M=Cr,Gd)
Authors: Sauer CH. , Landes J. , Zinn W. , Ebert H.
Published: March 2011

The temperature dependence of the magnetic hyperfine (hf.) fields near the interfaces in epitaxial Fe/Cr and partly epitaxial Fe/Gd bilayers were measured using 57Fe Conversion Electron Mössbauer Spectroscopy (CEMS). It was found that the Fe-Cr magnetic interaction extends only up to the second Fe-neighbor at the Fe/Cr interface, whereas the interaction range at the Fe/Gd interface is four times larger. For comparison the hf. fields and magnetic moments for Fe/Cr multilayers were obtained performing LMTO (Linear Muffin Tin Orbital) band structure calculations. The Néel temperature of a thin Cr-interlayer in a Fe/Cr/Fe sandwich structure was determined in dependence of the Cr-layer thickness.
Long and Short Range Oscillatory Exchange Coupling in Fe/Cu and Co/Cu Magnetic Multilayers
Authors: Herman F. , Sticht J. , Schilfgaarde M. Van
Published: March 2011

By carrying out accurate first-principles superlattice calculations, we determined the exchange coupling in bcc Fe/Cu and fcc Co/Cu multilayers as a function of the Cu spacer thickness. The fact that we can obtain long-range oscillatory coupling directly from first principles suggests that our theoretical model includes the underlying physical mechanism, and that such coupling is indeed a band structure effect. The exchange coupling depends on the interfacial orientation as well as on the Cu spacer thickness. In bcc [001] Fe/Cu, fcc [001] Co/Cu, and fcc [110] Co/Cu, the coupling has both long and short-range oscillatory components, while in fcc [111] Co/Cu, the long-range component dominates. Using a simplified model for the Fermi surface of the Cu spacer, we can relate the short-range oscillations to electronic transitions across the Fermi sphere, and the long-range oscillations to electronic transitions between spheres in adjacent zones in extended k-space, i.e., to interzonal transitions.
Magnetism in 4d Transition Metal–Ag(001) Sandwiches
Authors: Clougherty Dennis P. , Mchenry M. E. , Maclaren J. M.
Published: March 2011

Using ab-initio spin-polarized layer Korringa-Kohn-Rostoker (LKKR) band structure calculations, we investigated the possibility of having a stable ferromagnetic ground state in 4d transition metal (TM)–Ag(001) sandwiches (TM = Tc, Ru, Rh, and Pd). In contrast to recent calculations performed on systems with TM overlayers on Ag (001), we find that the TM sandwich configuration gives a paramagnetic ground state. While excellent agreement in general is obtained for the layer-projected densities of states (LDOS), the sandwich configuration lowers the densities of states at the Fermi energy (EF) in the case of Rh and Ru by a small amount which seemingly prevents the marginal ferromagnetic instability predicted by Eriksson et. al. (Phys. Rev. Lett. 66, 1350 (1991)) from occurring.
Substructure-Magnetic Property Correlation in Co/ag Composite Thin Films
Authors: Reed C.P , Deangelis R.J. , Liou S.H. , Nafis S. , Woollam John A. , Lee K.W. , Jacob R.J.
Published: March 2011

Three series of nanostructured, μm thick, Co/Ag composite thin films (13, 39 and 61 volume % Co) were produced by dc magnetron sputtering at various substrate temperatures (100–600°C) to determine their magnetic properties and characterize the microstructure. The films were found to be composed of finely dispersed Ag and Co particles. The film surfaces become rougher as the substrate temperature was increased. The crystal lattice structure of the Co was found to be fcc except at the lower substrate temperatures (<300°C) in the 61 volume % films where it was found to be a mixture of fcc and some hcp. The average diffracting particle size of both the Co and Ag rich phases increase with substrate temperature. The magnetic coercivity of the films reached a maximum value when the Co particle size was between 100–150Å.
Small d-Spacing and Internal Stress of Co-Cr Films Deposited by Kr Ion Sputtering
Authors: Akiyama S. , Nakagawa S. , Naoe M.
Published: March 2011

It is important to control the internal stress of the deposited film because the magnetic tape is becoming thinner for attaining higher recording density per volume. Kr gas was used as the working gas in the facing targets sputtering (FTS) system for depositing Co-Cr films. Kr gas has the larger ionization cross section and atomic mass than those of Ar, Co and Cr, so that Kr gas could make stable discharge at lower pressure and the recoiling of Kr atoms on the surface of the Co-Cr target was more effectively suppressed. Therefore, Kr ions seem to be more advantageous as working gas than Ar ions which are the most common working gas. The FTS method with Kr ions could deposit the stress-free Co-Cr films with good crystallinity. Actually, Δθ50 and (Mr/Ms) of Co79Cr21 films deposited on Si wafer by Kr ion sputtering in the pressure range of 10–4 ∼ 5×10−−5 Torr were as small as 4% and 0.1, respectively. The colpressive stress of 1500Å-thick Co79Cr21 films was as small as 108 dyne/cm2, of which the value was smaller than 10% of that by Ar ion sputtering. Therefore, the combination of the FTS method and Kr gas seems to be very convenient for solving the problem of the internal stress.
Spin-Polarized Scanning Tunneling Microscopy (SPSTM)
Authors: Wiesendanger R. , Buergler D. , Tarrach G. , Shvets I.V. , Guentherodt H.-J.
Published: March 2011

We report on a novel promising technique for the investigation of magnetic structures at surfaces at high spatial resolution, ultimately down to the atomic scale. This technique is based on the observation of vacuum tunneling of spin-polarized electrons by means of a scanning tunneling microscope (STM). We discuss appropriate probe tips for the spin-polarized STM (SPSTM) and describe initial experimental results. We further focus on the information obtained by SPSTM. Finally, the perspectives of SPSTM will be discussed.
Micro- and Nanostructure of Co/Pd and Co/Au Multilayers Studied with Transmission Electron Microscopy
Authors: Hakkens F. , Coene W. , Broeder F.J.A. Den
Published: March 2011

Several metallic multilayers with very thin magnetic Co layers display a preferred magnetization perpendicular to the interfaces. There are strong indications that the magnitude of this anisotropy depends critically on details of the microstructure of the multilayers, and especially on the atomic structure of the interfaces. The micro- and nanostructure of Co/Pd and Co/Au multilayers, which exhibit a large difference in lattice parameter (9% and 14% respectively), was studied by conventional transmission electron microscopy (TEM) and high resolution TEM (HREM). The multilayers, grown by vapor deposition, show a columnar structure and have a convex curvature in the growth direction. In Co/Au multilayers also the Au lattice is bent. Misfit dislocations are observed at the interfaces even for Co layers of one atomic layer thickness. Generally the interfaces show atomic roughness, which is more severe for Co/Au than for Co/Pd.
The Role of Next-Nearest Neighbors in The Neel Model of Surface Anisotropy for BCC Crystals
Authors: White Robert L. , Clemens Bruce M.
Published: March 2011

We have extended the Neél model of surface anisotropy in b.c.c. crystals to include next nearest neighbor interaction. Fitting the experimental data for Fe (001) and (110) surfaces leads to some pradoxes which cast doubt on the Neél surface anisotropy as the dominant source of surface anisotropy in thin films.
Magnetoelastic Interactions at Surfaces and Interfaces
Authors: O'Handley R. C. , Sun S.
Published: March 2011

The contribution of strains to anomalous surface and interface magnetic anisotropies cannot be analyzed quantitatively without knowledge of the ME coupling coefficients there. We have measured the ME coupling coefficients Bs near the surface (~0.5nm) of two amorphous alloys, Fe77Cr6B17 (with bulk magnetostriction λs = +7 × 10−6) and Co76Cr4B20 (λs = -3.8 × 10−6) and found them to differ significantly from the bulk values Bb: Fe-base, Bs = -1.7 × 105 J/m3 (57% of Bb) and Co-base, Bs = 5.8 × 105 J/m3 (three times Bb).
Photochenistry And Photophysics Of Materials In Zeolites.
Authors: Iu Kai-Kong , Liu Xinsfleng , Thomas J. Kerry
Published: March 2011

Pyrene is used as a molecular probe to study surface polarity, constrained character of diffusion, oxygen diffusion, effects of coadsorbed water, and exchange cations in zeolites A, X and Y. The experimental methods include both steady-state and time-resolved fluorescence spectroscopy, and diffuse reflectance absorption spectroscopy. The properties of CdS and TiO2 constructed in zeolites are also presented.
PbI2 Confined In The Spaces Of LTA Zeolites
Authors: Terasaki O. , Tang Z. K. , Nozue Y. , Goto T.
Published: March 2011

PbI2 clusters confined in spaces of LTA zeolite are successfully prepared through vapour phase. An HREM image showed that the crystallinity of the zeolite was preserved after preparation and showed directly that the clusters were incorporated into the α-cages. Absorption spectra were measured by diffuse reflection method as a function of loading density of PbI2 molecules. Several absorption bands from different cluster sizes were observed and showed remarkable blue shift. At the maximum loading, extra reflections, which are forbidden for Fm3A of LTA, were observed in electron and X-ray diffraction patterns. The appearence of the extra reflections and the dependence of absorption curve on the loading density suggest that superlattice of clusters was produced. The characteristic feature of zeolites as containers to make an artificial superlattice of clusters is pointed out.
Molecular Design Of Aluminosilicate Thin Film Devices
Authors: Creasy Kenneth E. , Deng Ying Ping , Park Jongman , Borgstedt Eric V. R. , Davis Shawn P. , Suib Steven L. , Shaw Brenda R.
Published: March 2011

Thin film coatings of NaY, NaA and ZSM-5 zeolites have been grown on copper and platinum substrates. Such materials have ion-exchange properties, molecular sieve pore size distribution, zeolitic surface areas and are crystalline. Size and charge selective electrodes, oxygen reduction fuel cells, and thin layer chromatography devices have been produced with these materials.
The Physicochemical Properties Of Vpi-7: A Microporous Zincosilicate With Three-Membered Rings
Authors: Annen Michael J. , Davis Mark E. , Higgins John B. , Schlenker John L.
Published: March 2011

The synthesis of materials with void volumes in excess of 50% is an ongoing challenge in molecular sieve science. It has been shown that a correlation exists between the minimum framework density (FD) and the smallest ring in which all tetrahedral atoms reside (MINR). Based on this evidence it appears that materials containing 3-membered rings (3MR) will be necessary in order to obtain FDs lower than those currently attainable. Several framework beryllosilicate minerals including the natural zeolite, lovdarite, contain 3MRs. Unfortunately, beryllium can form highly toxic compounds that limit its suitability for many applications. Thus, in this study we have searched for a replacement for Be and have found that zinc is a suitable substitute with respect to the formation of three-membered rings.

We report here VPI-7, a novel zincosilicate molecular sieve which contains three-membered rings. The VPI-7 framework contains rings composed of 3–, 4– and 5 T-atoms which form unidimensional 8– and intersecting 9MR channels.
Novel And Promising Applications Of Molecular Sieves In Organic Synthesis And Their Contribution To Environmental Protection
Authors: Hoelderich Wolfgang F.
Published: March 2011

Zeolite catalyts have acquired considerable technical and economical importance in refinery technology and petrochemistry. Over the past ten years, the search for applications of zeolite catalysis in the synthesis of organic intermediates and fine chemicals has been stepped up. An important aspect in this development is the changeover of reactions carried out over homogeneous catalysts to heterogeneous zeolite catalysis.

From this range of applications, it is intended to present two selected processes. These are the synthesis of pivalic acid and -caprolactam. The dependence on test parameters and on the catalyst properties such as acidity and doping, is described. A comparison is made with the conventional process carried out industrially. The advantages and disadvantages of the zeolite-catalyzed process are weighed up against one another.

The production of ε-caprolactam and pivalic acid by heterogeneous catalysis over zeolite catalysts offers a genuine alternative to the industrial processes employing homogeneous catalysis, particularly from the point of view of environmental protection, since the use of toxic BF3and NH2OH as well as the inevitable coproduction of ammonia sulfate is avoided.
An Investigation of Buried Layer Formation by 40keV Oxygen Implantation Into Silicon
Authors: Li Y. , Kilner J. A. , Chater R. J. , Tate T. J. , Hemment P. L. F. , Nejim A.
Published: March 2011

Device grade single crystal <100> silicon wafers have been implanted with 40keV oxygen ions over a dose range of 2×1017 to 8×1017/cm2 at a temperature of 5507±10°C. The specimens have been analyzed, both before and after high-temperature annealing at 1320°C for six hours, using SIMS, RBS, and TEM. During implantation a continuous buried SiO2 layer forms when the dose after which the buried SiO2 layer grows primarily toward the surface. After annealing samples implanted with the doses of both 2×1017 and 3×1017/cm2 it was observed that a defective SIMOX like structure was formed. Implanting with a dose of 4×1017/cm2 results in pit formation in the silicon overlayer. For the sample implanted with a higher dose of 5×1017/cm2, a non-continuous poly-crystalline silicon “overlayer” was formed. It would thus appear that when a single step implantation route is chosen, there is a dose (or layer thickness) limit for the production of a thin film SIMOX structure.
Effect of Intermediate Thermal Processing on Microstructural Changes of Oxygen Implanted Silicon-on-Insulator Material
Authors: Lee J. D. , Park J. C. , Krause S. J. , Roitman P. , El-Ghor M. K.
Published: March 2011

The microstructural changes in oxygen implanted silicon-on-insulator material (SIMOX) at intermediate annealing steps and the changes by rapid thermal annealing (RTA) were studied with transmission electron microscopy. Defects found in as-implanted SIMOX, including multiply faulted defects, short stacking faults, and {113} defects, were all removed in anneals from 900°C to 1100°C. The threading dislocations in annealed material form at these temperatures during thermal ramping. RTA shows that the microstructure is significantly influenced by the ramp rate. The very high ramp rate in RTA results in very flat interfaces and a buried oxide layer with no Si islands, but significantly increases the defect density. Overall, the results show that intermediate thermal processing steps strongly affect the final microstructure of SIMOX material.
Avoiding Dislocation Formation for B, P, and As Implants in Silicon
Authors: Liefting J. R. , Raineri V. , Schreutelkamp R. J. , Custer J. S. , Saris F. W.
Published: March 2011

Implants of B, P, and As in Si lead to dislocation formation after 900°c annealing if a critical amount of implant damage is exceeded. However, it is possible to implant higher doses without forming dislocations if the dose is implanted in several sub-critical steps. Annealing between each step removes the (sub-critical) implant damage and dislocations do not form. Such avoidance of dislocation formation is demonstrated for 80 keV implants of B and MeV implants of B, P, and As.
C Implantation for Suppression of Dislocation Formation
Authors: Liefting J. R. , Custer J. S. , Saris F. W.
Published: March 2011

This paper will show that annealing of Si implanted with moderate doses of 725 keV B results in the formation of secondary defects, the so-called category I dislocations. Surprisingly, 12C, with roughly the same mass as 11B, behaves in a very different way. Carbon implant damage does not result in dislocation formation even for damage levels > 100 times higher than that required for B implants. C is also able to avoid dislocation formation of co-implanted B ions. The C-dose needed to avoid dislocation formation for the B implant increases nonlinearly with B-dose. Special C-related secondary defects remain after annealing if the C-dose is higher than 4×1015 /cm2.
X-Ray Diffraction Analysis of Damage and Doping Effects in Low-Dose, High-Energy Implanted Silicon
Authors: Klappe Jos G.E. , Bársony István , Ryan Tom W.
Published: March 2011

High-Resolution X-Ray Diffraction is investigated as a technique for analysis of low-dose, high-energy implanted (001) silicon. The choice of the proper Bragg reflection for the rocking curve measurements is showed to be of crucial importance. The (026)1 reflection appears to be the most suitable for strain caused by implantation damage. By a qualitative analysis of rocking curves taken on B and P implanted Si samples, it could be established that the minimum dose, for which HR-XRD is sensitive enough, is about 1.5.1014cm−2 and 5.1013cm−2 for P and B, respectively. The necessary minimum peak temperature that was determined for a complete damage anneal with the T-RTA of P implanted Si with energies ranging from 0.5 to 1.5 MeV, was 1400 K for all doses of P considered. For B the required optimum peak temperature is about 1375 K.
Dependence of Profiles of Arsenic Implanted into Silicon on Tilt and Rotation Angles
Authors: Yang S. , Park C. , Klein K. , Gupta P. , Tasch A. , Simonton R. , Lux G. , McGee C.
Published: March 2011

We have performed a comprehensive experimental study of profiles of arsenic implanted into (100) silicon for a wide range of energies, doses, tilt angles, and rotation angles. Critical angles for channeling of arsenic ions in single-crystal silicon have been calculated and are found to agree well with experimental results. The <100> axial channels and the {110} planar channels are found to be primary sources of channeling. The optimal tilt and rotation angles which minimize channeling and maximize uniformity across a wafer are deduced.
Thermal Annealing of Shallow Implanted Phosphorus in Si(100)
Authors: Yu Ning , Ma K. B. , Zhang Z. H. , Chu W. K. , Kirschbaum C. , Varahramyan K.
Published: March 2011

The effect of channeling on the diffusion of ion implanted phosphorus in silicon has been investigated. Silicon samples, implanted with 25–100 keV P along the [100] channeling and the random equivalent directions, were subjected to thermal annealing over a temperature range of 600–1050 °C. Secondary Ion Mass Spectrometry (SIMS) and Spreading Resistance Probe (SRP) have been used to determine the atomic and carrier concentration depth profiles, respectively. The findings show that after annealing, the P profiles by implantation along the random equivalent direction can be kept shallower than the profiles obtained by implantation along the [100] channeling direction. Through proper annealing and electrical activation, only minimal diffusion in the tail region of the profiles occurred. For 50 keV P at 1×1015 at./cm2, changing the implantation from the [100] to the random equivalent direction leads to a reduction in the profile depth of about 50% (at 1×1017at./cm3). After 10 seconds of rapid thermal annealing (RTA) at 1050 °C, the profile depth remains more than 30% shallower than the channeled profile.
A New Computationally-Efficient Two-Dimensional Model for Boron Implantation Into Single-Crystal Silicon
Authors: Klein K. M. , Park C. , Yang S. , Morris S. , Do V. , Tasch A. F.
Published: March 2011

We have developed a new computationally-efficient two-dimensional model for boron implantation into single-crystal silicon. This new model is based on the dual Pearson semi-empirical implant depth profile model [1] and the UT-MARLOWE Monte Carlo boron ion implantation model [2]. This new model can predict with very high computatational efficiency two-dimensional as-implanted boron profiles as a function of energy, dose, tilt angle, rotation angle, masking edge orientation, and masking edge thickness.
Energetic Electron Beam Induced Recrystallization of Ion Implantation Damage in Semiconductors
Authors: Bench M. W. , Robertson I. M. , Kirk M. A.
Published: March 2011

Isolated amorphous zones produced in GaAs, GaP, Si, and Ge by the implantation of 50 keV Kr+ or Xe+ ions have been induced to recrystallize under the influence of the electron beam in the transmission electron microscope. This effect has been investigated as a function of electron irradiation temperature and beam energy in the TEM. Temperature effects were investigated through irradiations performed at 30 and 300 K. The electron energies used ranged from 50–300 keV in the 300 K experiments and 200 keV electrons were used at 30 K.

Recovery was induced in all of the materials even at electron energies below the threshold displacement energy indicating production of point defects within the crystalline material is not required to induce regrowth. In GaAs and GaP, recovery occurred for all electron energies studied, down to 50 keV. In Si, the beam induced regrowth rate approaches zero at an energy of 80 keV with the recovery rate increasing with increasing electron energy. At 30 K, the 200 keV electron beam induced recrystallization in all cases studied (GaAs, GaP, and Si).
Radiation-Enhanced Plastic Flow of Covalent Materials During Ion Irradiation
Authors: Volkert C. A. , Polman A.
Published: March 2011

Plastic deformation of several covalently-bound materials has been studied during ion irradiation. In all of these materials, namely crystalline and amorphous silicon, crystalline and amorphous Si0.9Ge0.1, and amorphous SiO2, the damage created by the ion beam causes density changes in the irradiated region which eventually saturate with ion dose. In the crystalline materials, the density changes were accompanied by a transformation to the amorphous phase. Superimposed on the density changes is plastic deformation which occurs during irradiation of both crystalline and amorphous materials to relieve stresses in the irradiated region. A wafer curvature measurement technique has been developed which allows the contributions from density changes and plastic deformation to be distinguished and the stress dependence of the plastic deformation to be determined.

In all of the amorphous materials, the plastic deformation is Newtonian viscous shear flow, which is characteristic of solids where deformation is governed by the diffusive motion of point defects. The radiation-enhanced shear viscosity per ion was flux-independent, revealing that flow occurs rapidly, probably within the localized damaged regions created by each ion. This viscosity does not depend strongly on the material. In fact, similar viscosities were obtained during measurements of radiation-enhanced plastic deformation of crystalline covalent samples and polycrystalline aluminum films.
Distribution and Characterization of Iron in Implanted Silicon Carbide
Authors: Bentley J. , Romana L. J. , Horton L. L. , McHargue C. J.
Published: March 2011

Analytical electron microscopy (AEM) and Rutherford backscattering spectroscopy-ion channeling (RBS-C) have been used to characterize single crystal α-silicon carbide implanted at room temperature with 160 keV 57Fe ions to fluences of 1, 3, and 6×1016 ions/cm2. Best correlations among AEM, RBS, and TRIM calculations were obtained assuming a density of the amorphized implanted regions equal to that of crystalline SiC. No iron-rich precipitates or clusters were detected by AEM. Inspection of the electron energy loss fine structure for iron in the implanted specimens suggests that the iron is not metallically-bonded, supporting conclusions from earlier conversion electron Mössbauer spectroscopy (CEMS) studies. In-situ annealing surprisingly resulted in crystallization at 600°C with some redistribution of the implanted iron.
Annealing of Pb-Implanted SrTiO3 in The Presence of Water Vapour: A Study Using D218O Labelling
Authors: McCallum J. C. , Simpson T. W. , Mitchell I. V. , Rankin J. , Boatner L. A.
Published: March 2011

We report new measurements of the regrowth behaviour of Pb-implanted SrTiO3 crystals in the presence of water vapour. Doubly labelled water vapour, D218O, at greater than 95% enrichment in each isotope has been added to the annealing ambient and depth profiles of D and 18O have been obtained from the regrown crystals using secondary ion mass spectrometry (SIMS). The D and 18O content has also been measured by nuclear reaction analysis (NRA) using the reactions D(3He,p)4 He and 18O(p,α)15 N. The crystals were regrown in a conventional furnace under a controlled gas ambient and time-resolved optical reflectivity (TRR) was used to dynamically monitor the regrowth rate during the anneal. An enhancement of the solid-phase epitaxial regrowth rate is observed when water vapour is added to the annealing ambient. This rate increase is accompanied by incorporation of D throughout the regrown layer. 18O is incorporated into the lattice but does not appear to penetrate deep enough to influence the regrowth rate.
Examination of Ion Beam-Target Angle Effects by Optical Spectroscopic Profiling
Authors: Klein J. D. , Yen A.
Published: March 2011

The optical emission spectra resulting from ion beam sputtering a SrTiO3 target were observed as a function of position. A collimated optical fiber bundle parallel to the plane of die sputter target was translated vertically and horizontally to spectroscopically profile the sputter process. Three different angles of incidence of the beam to die target were examined for evidence of bombardment of candidate substrate positions by undesirable species. When the ion beam was at normal incidence to the target or 22.5* from normal incidence the Ar and O contours were of similar shape. However, when die target was inclined at an angle of 45* to die incident ion beam die O contours deviated markedly. Under these conditions it appears that there is a substantial oxygen flux in a direction normal to die target surface. Under these conditions die placement of a substrate facing die sputter target would probably result in undesirable bombardment of die growing film by energetic oxygen.
Irradiation Damage in Zr3 Fe
Authors: Hove L. M. , Rainville M. H. , Phillips D.
Published: March 2011

Ion bombardments, transmission-electron-microscopy (TEM) and analytical-electron-microscopy (AEM) techniques were used to obtain information on the effect of irradiation on the phase stability of Zr3 Fe, which has an orthorhombic crystal structure. Irradiations were performed at 35–773 K using 0.5–1.5 MeV 40Ar ions and at 40 K using 15–120 keV 209Bi ions.

At low ion fluences (1011–1013 ions cm−2), most of the visible damaged regions (∼1.0–5.0 nm diameter) exhibited strong structure-factor contrast features and it is believed that they are probably amorphous. With increasing ion energy, multiple damaged regions were observed to form within individual collision cascades, and the fraction of the theoretical cascade volume occupied by these heavily-damaged regions decreased rapidly. Irradiations at higher ion fluences showed that an irradiation-induced phase change from the crystalline-to-amorphous state occurred at 35–573 K, but not above 623 K. The effect of varying the ion flux was also investigated. The results showed that the fluence required to amorphize a given fraction of the irradiated volume was quite dependent upon the amount of annealing that occurred within the collision cascade at the temperature of the bombardment. The crystalline-to-amorphous transformation appeared to be the result of direct amorphization within the collision cascades and a critical defect concentration being reached in the cascade overlap regions, thus producing additional amorphous regions.
Implantation of Nitrogen into Ti/Al, Ni/Ti, and Ni/Al Bilayers
Authors: Boerma D. O. , Corts T.
Published: March 2011

Ti/Al, Ni/Ti, and Ni/Al bilayers were produced by evaporation on a Si substrate. The thicknesses of the composing layers were in the 50–200 nm range. The as-evaporated bilayers were implanted with doses of 0.4–2.5 · 1017 of 15N ions/cm2. The 15N energy was chosen so that the calculated projected range was either in the middle of the top Ni layer, or coincided with the interface between the metal layers. The implantation temperature was varied in the range from 25 °C to 245 °C. The 15N depth profiles as measured with nuclear reaction analysis (NRA) were found to have the expected Gaussian shape for the Ti/Al bilayers. However, in the Ni/Ti and Ni/Al layers very asymmetric 15N profiles were observed, with a major fraction of N atoms in the Ti or Al layer, and a minor fraction in the Ni layer. The N concentrations in the Al or Ti layers were found to be almost constant. A massive redistribution of N atoms must have taken place in all three metals during the implantations, to form the observed profiles. We speculate that this remarkable phenomenon, which occurs even below 80°C, can be explained by interstitial diffusion of N atoms and subsequent trapping in Ti or Al, which have a high chemical affinity for nitrogen. The N atoms remaining in the Ni layer after implantation were found to migrate out of this layer during annealing at temperatures ≥250°C.
Molecular Dynamics Simulations of Low Energy Displacement Cascades in the Ordered Compound CuTi
Authors: Zhu H. , Lam N. Q. , Devanathan R. , Sabochick M. J.
Published: March 2011

The properties of low-energy (≤500 eV) displacement cascades in the ordered intermetallic compound CuTi have been investigated by molecular dynamics simulations in conjunction with recently-developed embedded-atom potentials. Various aspects of the time evolution of cascades produced by Cu and Ti primary knock-on atoms have been considered, including the dynamics of Frenkel-pair production, generation of ‘pure’ replacements and anti-site defects, and the anisotropy of the threshold energy for displacement. The spatial distributions of Frenkel defects and the damage function have been analyzed, based on information obtained from various simulated events corresponding to different recoil directions.