bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure And Properties Of BPDA-PDA Polyimide From Its Poly(Amic Acid) Precursor Complexed With An Aminoalkyl Methacrylate
Authors: Ree Moonhor , Nunes Thomas L. , Chen K.-J. Rex , Czornyj George
Published: March 2011

BPDA-PDA poly(amic acid) precursor was functionalized through its carboxylic acid groups being linked with a crosslinkable aminoalkyl methacrylate, 2-(dimethylamino)ethyl methacrylate (DMAEM), by acid/base complexation. BPDA-PDA polyimide films, which were thermally imidized from the precursors complexed with various amounts of DMAEM, were characterized by means of wide angle x-ray diffraction, stress-strain analysis, and residual stress analysis. The structure and properties of the BPDA-PDA polyimide film were dependent upon the history of the precursor, that is, the complexation of the poly(amic acid) precursor with DMAEM. The molecular packing order was enhanced with the history of DMAEM loading while the molecular order along the chain axis was disrupted. Overall, physical properties, such as mechanical properties and residual stress, were degraded with DMAEM loading. The moisture induced stress relaxation behavior was sensitive to the history of DMAEM loading, whereas the creep induced stress relaxation was varied little due to its high Tg. These properties are understood in terms of structure/property relationships, as well as microvoids, which were possibly generated by outgassing the bulky DMAEM pendent groups during thermal imidization.
Chemistry and Characterization Of Polyimides Derived from Poly(Amic Alkyl Esters)
Authors: Volksen Willi , Yoon D. Y. , Hedrick J. L. , Hofer D.
Published: March 2011

The modification of the pendant acid groups along the poly(amic acid) backbone in the form of alkyl ester groups leads to greatly improved polyimide precursors. These poly(amic alkyl esters) are characterized by the absence of hydrolytic instability due to elimimation of the “monomer-polymer” equilibrium associated with poly(amic acids), a broad imidization temperature regime, improved solubility characteristics, and enhanced mechanical properties. In the absence of hydrolytic instability, it is now possible to use an aqueous work-up of the polyimide precursor. This presents an attractive synthetic pathway for the preparation of well-defined, amine-terminated oligomers. Such oligomers can then be utilized both in the preparation of low molecular weight, chain-extendable polyimide precursors as well as polyimide block copolymers. The higher imidization temperatures offered by the “amic ester” chemistry allows for more efficient chain extension prior to imidization. Alternatively, the lack of the “monomer-polymer” equilibrium and accompanying propensity for monomer randomization reactions presents a potential pathway for the preparation of polyimide blends.
Spin Coating Planarization Of Integrated Circuit Topography On A Rotating Disk
Authors: Yonkoski Roger K. , Soane David S.
Published: March 2011

Polyimide is commonly used in the microelectronic industry for interconnection applications because of its ability to planarize features typically found on an IC chip. A mathematical model is developed to describe fluid flow on a rotating disk based on the principles of mass and momentum conservation. Constitutive relationships necessary for this model are proposed. Experimental data for polyimide precursor solutions are presented which enable the determination of parameters for the constitutive equations. This model is used to describe the film profiles over flat surfaces and near micron-sized features. Attention is focused on the coupling between mass transport and fluid flow as well as the effects of surface tension on film profiles over topographical features.
Protonation Effects On PPQ Polymer During HF Lift-Off Process Used In Multichip Module Fabrication.
Authors: Templier François , Torres J. , Clarisse C. , Palleau J.
Published: March 2011

The reactions between PPQ and several acidic solutions have been studied. Protonation reactions have been evidenced using U.V.- Visible spectroscopy. PPQ revealed three different states concerning these completely reversible reactions. Each state exhibits a specific colour: Pale yellow (as deposited PPQ), and gold yellow and purple red for, respectively, the first and the second protonation states. Using IR spectroscopy, it has been shown that the protons are fixed at the nitrogen sites of the polymer. A possible degradation of the PPQ related to the protonation reactions is also studied, and thus technological solutions are proposed.
Thermotropic Polyesters Containing Carbonyl Or Ether Linkages
Authors: Irwin Robert S.
Published: March 2011

In an assembly of aligned, thermotropic polyester macromolecules, such as a fiber, the flexibility and deviations from rectilinearity occasioned by in-chain ArCOAr or ArOAr units are reflected sensitively by overall stiffness (initial modulus) and elasticity (elongation at break). The influence of frequency and placement of these units, as well as the effect of ring substituents, is discussed.

In a few cases where carbonyl or other units are regularly placed at suitable intervals along the chain, the latter apparently is extended as a low amplitude, regular helix which, in terms of physical properties, approximates to a straight, rod-like conformation. In situations where the angulation created by a carbonyl unit is immediately cancelled by an adjacentm-phenylene ring, the extended macromolecule is virtually rectilinear and, though marginally liquid crystalline, may provide some of the strongest organic fibers known.
Structure And Properties Of Binary Rodlike/Flexible Polyimide mixtures.
Authors: Rojstaczer S. , Ree M. , Yoon D Y. , Volksen W.
Published: March 2011

Abbstract:

Binary mixtures of a rodlike poly(p-phenylene pyromellitimide) (PMDA-PDA) and a flexible 6F-BDAF polyimide synthesized from hexafluoroisopropylidene diphthalic anhydride and 2,2-bis(4-aminophenoxy-p-phenylene) hexafluoropropane were prepared by solution-blending of the meta-PMDA-PDA poly(amic ethyl ester) and 6F-BDAF poly(amic acid) precursors, followed by solvent evaporation and thermal imidization. The size scale of the phase separation, as measured by light scattering, is ca. I μm or smaller in most cases. Dynamical mechanical thermal analysis measurements indicate that the glass transition temperature of 6F-BDAF is unaffected in all of the mixtures studied, indicating complete demixing of rodlike and flexible polyimides in agreement with theory. X-ray photoelectron spectroscopy results show a strong surface segregation of 6F-BDAF in mixtures containing as low as 10% by weight of the 6F-BDAF component in the bulk. The mixtures with PMDA-PDA as the major matrix component therefore maintain excellent bulk properties of rodlike polymers, i.e., high modulus to 500°C, and low coefficients of thermal expansion (< ca. 10 ppm/°C). On the other hand, the surface properties of the mixtures are dominated by the flexible 6F-BDAF, resulting in excellent polymer/polymer self-adhesion (lamination) properties between fully imidized films.
Growth Of Polyimide Films By Chemical Vapor Deposition And Their Characterization
Authors: Kowalczyk Steven P. , Dimitrakopoulos Christos D. , Molis Steven E.
Published: March 2011

A dry ultra high vacuum technique for the preparation of polyimide films is investigated as an alternative to standard wet processing techniques involving the use of solvents. This technique is based on the co-deposition of monomers (pyromellitic dianhydride and oxydianaline in this study) to form polyimide (poly (4,4′-oxydiphenylenepyromellitimide)). Various parameters to optimize film growth are investigated and the properties of the films are compared to films prepared by spin casting from solution. Films from 10Å to 15 μ were grown. Uniform films over 3 inch wafers were successfully grown. Many properties such as adhesion, dielectric constant and stress were similar to spun films. H-lowever, these films did exhibit more crystalinity but less orientation than the spun films. Finally, being a vapor phase process the rdms were conformal rather than planar.
Imide-Aryl Ether Ketone Block Copolymers
Authors: Hedrick J. L. , Volksen W. , Moiianty D. K.
Published: March 2011

Imide-aryl ether ketone block copolymers were prepared and their morphology and thermal and mechanical properties investigated. The key feature of this copolymerization is the preparation of soluble aryl ether ketimine oliogmers which may be subsequently hydrolized to the aryl ether ether ketone form. A bis(amino) aryl ether ketimine oligomer was prepared via a nucleophilic aromatic substitution reaction with a molecular weight of 6,000 g/mol. The oligomer was co-reacted with 4,4′-oxydianiline (OI)A) and pyromellitic dianhydride (PMDA) diethyl ester diacyl chloride in N-methyl-2-pyrrolidone (NMP) in the presence of N-methylmorpholine. The copolymer compositions, determined by II-NMR, of the resulting amic ester based copolymers ranged from 8 to 20 wt% aryl ether ketimine content. Prior to imide formation, the ketimine moiety of the aryl ether ketimine block was hydrolyzed (p-toluene sulfonic acid) to the ketone form producing the aryl ether ether ketone block. Solutions of the copolymers were cast and cured to effect imidization, producing clear films. The copolymers displayed good thermal stability with decomposition temperatures in excess of 450°C. Multiphase morphologies were observed irrespective of the co-block type or composition.
Photorefractive Properties of Cobalt-Doped Barium
Titanate
Authors: Chang J. Y. , Garrett M. H. , Jenssen H. P. , Warde C. , Tayebati P.
Published: March 2011

A series of cobalt-doped barium titanate crystals were grown that have high
beam-coupling gain. Our photorefractive characterization shows that with
increasing cobalt concentration in the crystal a deep level is formed and
the relative effect of shallow levels on the space-charge field amplitude
diminishes. This gives the crystal a long dark storage time. We find that
cobalt-doping in barium titanate increases the two-beam coupling gain by
reducing the dark conductivity and increasing the total effective trap
density.
Low Temperature Growth of Gaas Quantum Well Lasers by Modulated
Beam Epitaxy
Authors: Xin S. , Longenbach K. F. , Schwartz C. , Jiang Y. , Wang W. I.
Published: March 2011

GaAs single quantum well lasers have been successfully grown at low
temperatures by a modulated beam epitaxy process in which the Al/Ga flux is
held constant while the As flux is periodically shut off to produce a
metal-rich surface. Devices grown at a substrate temperature of 500 °C
exhibit threshold current densities below 1 kA/cm2. This value is
lower than normally grown low temperature lasers and is the lowest achieved
by any low substrate temperature growth technique. In addition, low
temperature (10 K) photoluminescence of single quantum wells grown with this
technique exhibit full-width half maximum values, comparable to that
attainable by higher temperature growth techniques. The improved quality of
these low temperature grown quantum structures is attributed to both a
smoothing of the growth front and a reduction of excess As during the
modulated beam epitaxy process. The high growth rates and less frequent
shutter operation of this technique make it a more practical than migration
enhanced epitaxy or atomic layer epitaxy for low temperature growth.
Strained InGaAs/GaAs Multiple Quantum Wells Grown on Planar and
Pre-Patterned GaAs(100) Substrates VIA Molecular Beam Epitaxy: Applications
to Light Modulators and Detectors
Authors: Chen Li , Hu Kezhong , Rajkumar K. C. , Guhae S. , Kapre R. , Madhukar A.
Published: March 2011

We report the realization of high quality strained InGaAs/GaAs multiple
quantum wells (MQW) grown on planar GaAs (100) substrates through
optimization of molecular beam epitaxical (MBE) growth conditions and
structure. Such MQWs containing ∼ 11% In have lead to the realization of an
asymmetric Fabry-Perot (ASFP) reflection modulator with a room temperature
contrast ratio of 66:1 and an on-state reflectivity of 30%. For In
composition ≥ 0.2, the improved optical quality for very thick (gt;2μm)
InGaAs/GaAs MQWs grown on pre-patterned substrates is demonstrated via
transmission electron microscopy (TEM) and micro-absorption
measurements.
Modulator Structure Using In(As, P)/lnP Strained Multiple
Quantum Wells Grown By Gas-Source MBE
Authors: Hou H. Q. , Chin T. P. , Liang B. W. , Tu C. W
Published: March 2011

In(As, P)/InP strained multiple quantum wells (SMQW's) were grown with
gas-source molecular-beam epitaxy (GSMBE). A successful control of the As
composition was achieved over a wide range by using two techniques.
High-quality samples were characterized structurally and optically by x-ray
diffractometry, transmission electron microscopy (TEM), photoluminescence
(PL) and absorption measurements. Excitonic emission energy and the critical
layer thickness of In(As, P)/InP SMQW's are calculated as a function of the
As composition. The results show that 1.06, 1.3 and 1.55 μm excitonic
emission can be achieved at room temperature using this material system. We
also discuss the perspective of using In(As, P)/InP SMQW's for modulator
application.
On The Photoemission From Quantum Confined Compound
Semiconductors
Authors: Ghatak Kamakhya P. , De B.
Published: March 2011

In this paper, we have studied the photoemission from quantum wells (QWs),
quantum well wires (QWWs) and quantum dots (QDs) of degenerate Kane-type
semiconductors, on the basis of a newly derived electron dispersion law
considering all types of anisotropies within the framework of k.p formalism.
It is found, taking n-Cd3 As2 as an example, that the
photoemission increases with increasing photon energy in a ladder-like
manner and also exhibits oscillatory dependences with changing electron
concentration and with film thickness, for all types of quantum confinement.
The photoemission current density is greatest in QDs and least in QWWs. In
addition, the theoretical results are in agreement with the experimental
observation as reported elsewhere.
Nonlinear optical devices: Relative Status of Polymeric
Materials
Authors: Stegeman George I.
Published: March 2011

Nonlinear optical phenomena have been investigated over the last three
decades in many different materials and a great deal of progress has been
made in both the basic science and device applications.(1] Although interest
in nonlinear organic materials dates back to the early days of nonlinear
optics, it is only in the last five years that progress has been sustained
and rapid. The purpose of this paper is to examine progress in developing
new nonlinear organic materials and in their application to devices for
comparison with current state-of-the-art devices using other material
systems.
Molecular Beam Epitaxy of Znl-x Cdx
Se/ZnSe Heterostructures And Their Optical Properties
Authors: Luo H. , Samarth N. , Furdyna J. K. , Jeon H. , Ding J. , Pelekanos N. , Nurmikko A. V.
Published: March 2011

Superlattices and quantum wells of Znl-xCdxSe/ZnSe,
and heterostructures based on ZnSe/CdSe digital alloys have been grown by
molecular beam epitaxy (MBE). Their optical properties were studied with
particular emphasis on excitonic absorption and photopumped stimulated
emission. Excitonic absorption is easily observable up to 400 K, and is
characterized by extremely large absorption coefficients (α =
2×105cm−1). Optically pumped lasing action is
obtained at room temperature with a typical threshold intensity of 100
kW/cm2. The lasing mechanism in these II-VI quantum wells
appears to be quite different from that in the better studied III-V
materials: in our case, the onset of stimulated emission occurs
before the saturation of the excitonic absorption, and
the stimulated emission occurs at an energy lower than that
of the excitonic absorption.
Photoluminescence Study of Li-implantation into ZnSe Epitaxial
Layers Grown by Molecular Beam Epitaxy
Authors: Yasuda T. , Jin M. K. , Gaines J. , Merz J. L.
Published: March 2011

Lithium ion-implantation was performed on ZnSe layers which were grown on
GaAs substrates by MBE. Strong photoluminescence emission due to
acceptor-bound excitons was observed from samples implanted with lithium
doses of up to 1015cm−2 and annealed under optimized
conditions for rapid thermal annealing. Lithium implantation results in low
damage to the ZnSe as well as the formation of a shallow acceptor level.
Thermal degradation of both implanted and unimplanted epilayers caused by
the rapid thermal annealing was inviestigated at various annealing
temperatures. We find that, under certain annealing conditions, unimplanted
samples show greater thermal degradation than lithium implanted samples. The
photoluminescence spectrum of an unimplanted sample annealed at 800°C shows
considerable degradation; however, a lithium-implanted sample annealed at
the same temperature still shows strong luminescence in the excitonic
region.
Electroluminescence from p-n Junction Leds Consisting of N-Doped
and Cl-Doped ZnSe Layers
Authors: Ohkawa K. , Ueno A. , Mitsuyu T.
Published: March 2011

We have fabricated ZnSe p-n junction LEDs with a new structure of
Pt/p-ZnSe/n-ZnSe/n-GaAs. The dopant used for n-type ZnSe was Cl, and p-type
ZnSe:N was formed by nitrogen radical doping. The LEDs exhibited good
rectification properties. We have found that electroluminescence at 77 K was
dominated by recombination emission between free electrons and acceptor
holes at 2.705 eV. Increasing the temperature, recombination emission
between donor electrons and free holes dominated blue bandedge emission
region.
Second and third order Nonlinear Optical Properties of
Crystalline Inorganic / Organic Complexes.
Authors: Marcy Henry O. , Warren Leslie. F. , Davis Laura E. , Webb Mark S. , Velsko Stephan P.
Published: March 2011

The properties for members of a new class of nonlinear optical (NLO)
materials which stoichiometrically incorporate organic and inorganic
constituents into a single crystalline lattice are reported. Recent results
for our synthetic, crystal growth, and optical studies suggest that a number
of these relatively transparent “semiorganic” compounds have significant
second and/or third order NLO responses and often display favorable crystal
growth morphologies.

The prototype material of this class, zinc tris(thiourea) sulfate, or ZTS,
has a UV cutoff at about 325 nm, can be readily grown to cm3
sizes, and has been shown to be a highly efficient Type II frequency doubler
for 1064 nm Nd:YAG laser radiation. ZTS also possesses a moderate third
order nonlinear optical response (ca. 0.1 × CS2) which occurs on
at least a picosecond time scale as determined by degenerate four-wave
mixing (DFWM) experiments at 532 nm.

Refractive index, second harmonic generation, and DFWM data for a number of
these new compounds are presented.
Optical Second Harmonic Generation in
CdxZn1−xS and the
CdxZn1−xS:CdyZn1−yS
Superlattice System
Authors: Mullins J. T. , Taguchi T.
Published: March 2011

Optical second harmonic generation in epitaxial layers of
CdxZn1−xS and CdxZn1−xS:ZnS
and CdS:CdxZn1−xS strained layer superlattices which
had been removed from their substrates has been investigated. Some evidence
for resonant enhancement of the second order non-linear susceptibility has
been found for one sample where the onset of optical absorption was at
photon energies close to that of the second harmonic radiation.
Side Chain Polymers for Electro-Optic
Applications
Authors: DeMartino Ronald N. , Allen Diane E. , Keosian Richard , Khanarian Garo , Haas David R.
Published: March 2011

Organic and polymeric materials have emerged in recent years as candidates
for advanced device and systems applications. This interest has arisen from
the promise of extraordinary optical, structural, and mechanical properties
of certain organic materials, and from the fundamental success of molecular
design performed to create new materials.

Our approach to the problem is to develop an understanding of the molecular
basis of non-linear optical activity, incorporate the most promising
candidates into tractable polymers, and evaluate these materials in device
format. This paper will review some of the recent developments in the NLO
materials effort at Hoechst Celanese.
Magnetic and Transport Properties of Ag/Cr Metallic Superlattices
Authors: Kyuno Kentaro , Inoue Yasushi , Ogu Shinzo , Mae Kazuki , Kaneko Takeo , Yamamoto Ryoichi
Published: March 2011

The results of x-ray diffraction, resistivity and magnetization measurements of Ag/Cr metallic superlattices are presented. Dramatic changes in the interplanar distances of Ag and Cr were found as a function of the number of Cr monolayers in a period. The resistivities of the superlattices increased as the composition of Cr increased. Magnetization measurements show that the superlattice [Ag(10ML)/Cr(2ML)] exibits a maximum magnetic susceptibility.
On the Microstructure of a Ni3Al/SiC/TiB2 Intermetallic Matrix Composite Processed by Spray Atomization and Co-Deposition
Authors: Liang X. , Lavernia E. J.
Published: March 2011

This work reports on the microstructure of a particulate reinforced nickel aluminide composite synthesized by spray atomization and co-deposition. This synthesis methodology involved using high energy inert gas to disintegrate the nickel aluminide matrix (IC-396) into a Gaussian distribution of micrometer-sized, semi-solid droplets while simultaneously co-injecting SiC and TiB2 particulates, followed by deposition onto a water cooled substrate. The microstructure of the as-spray deposited composite material consisted of a mixture of the ordered γ (Ni3Al) and the disordered γ (Ni-rich) phase with a homogeneous distribution of SiC and TiB2 particulates. Scanning electron microscopy, combined with Energy Dispersive X-ray Spectroscopy were used to provide insight into the reactions taking place in the interfacial zone. The results of the present study show that a well defined reaction zone was formed at the Ni3Al/TiB2 interface; whereas extensive reaction occurred between the SiC particulates and matrix, resulting in complete transformation of almost all SiC particulates into other carbide phases.
Morphological Stability of Semicoherent Solid-Solid Interfaces: a Simple Model
Authors: Rottman Craig
Published: March 2011

The stability of semicoherent interfaces between two solids with small lattice mismatch is examined. I consider the cases in which the rotation θ between the two solids is both zero and small. The interface orientation, characterized by a single angle φ, is arbitrary. The interfaces are composed of regularly spaced misfit dislocations, steps, and lattice dislocations. For a wide range of φ, many flat interfaces are unstable with respect to breaking up into two interfaces of distinct orientations, one of which contains only one of the two types of dislocations possible.
Elastic Moduli of Metallic Multilayered Thin Films Ag/Cu, Al/Cu and Co/Cu Measured by Brillouin Scattering Method
Authors: Ito Toshiya , Yamamoto Ryoichi , Yoshihara Akira
Published: March 2011

The Rayleigh wave velocity of metallic superlattices Ag/Cu, Al/Cu and Co/Cu deposited by ion beam sputtering were measured as a function of layering period Λ using Brillouin scattering method. The VR-Λ relationship can be well interpreted using a phenomenological model consisting of three elastically different layers, i.e. two original and an intermediate layer. We have assumed in this model that the elastic modulus and the thickness of the intermediate layer are independent on the layering period.
Temperature Dependence of the Elastic Behavior of Structurally Disordered Metallic Superlattices
Authors: Jaszczak J. A. , Wolf D.
Published: March 2011

The structure and elastic properties of superlattices composed of high-angle twist grain boundaries on (100) planes of copper are investigated as a function of both the modulation wavelength and temperature via molecular dynamics simulations. Comparison is made with zero-temperature results, where a stiffening of the Young's modulus normal to the interfaces and a softening of the modulus for shear parallel to the interfaces has previously been observed. The differences between the effects of homogeneous (temperature-induced) and inhomogeneous (interface-induced) structural disorder on the elastic properties is explored.
Contamination Effects in Mo/Ni Superlattices
Authors: Hues Steven M. , Makous John L.
Published: March 2011

A softening of the shear elastic constant c44 has been observed previously in Mo/Ni superlattices as a function of decreasing bilayer thickness below approximately 100 Å.[1] We have prepared a series of Mo/Ni superlattice films by ion beam sputtering doped with varying concentrations of either aluminum or oxygen. The chemical and structural properties of these films were then determined using x-ray diffraction (XRD) and Auger electron spectroscopy (AES). The shear elastic properties were characterized by measuring the surface acoustic wave (SAW) velocity of the deposited films. We demonstrate structural and elastic property effects resulting from Al and O impurity incorporation in Mo/Ni multilayers.
Elastic Properties and Structural Evolution of AgNi Superlattices
Authors: Rodmacq B. , Pelosin V. , Hillairet J.
Published: March 2011

Silver-nickel multilayers were prepared by sputtering at 100 K. X-ray diffraction, electrical resistivity and dimensional variation measurements were performed to structurally characterize these stratified materials, both in the as-prepared state and during the course of annealing cycles. Clearly, polycrystalline superlattices with marked (111) texture perpendicular to the strata are formed. We studied the elastic properties of these superlattices by performing uniaxial tension tests. No deviation from linear elasticity was observed, whatever the period. Young's modulus was found to be 130±15 GPa for all the periods studied. Thus no significant functional dependence of Young's modulus on the stacking periodicity exists in the AgNi superlattice, in the range of periods explored, 2.6 to 18 nm.
Pulsed Laser Melting: The Effect of Implanted Solutes on the Resolidification Velocity
Authors: Galvin G. J. , Mayer J. W. , Peercy P. S.
Published: March 2011

Transient electrical conductance has been used to measure the resolidification velocity in silicon containing implanted solutes. Nonequilibrium segregation of the solutes occurs during the rapid resolidification following pulsed laser melting. The velocity of the liquid-solid interface is observed to depend on the type and concentration of the solute. A 25% reduction in solidification velocity is observed for an implanted indium concentration of three atomic percent. Implanted oxygen is also shown to reduce the solidification velocity. The dependence of the velocity on solute concentration impacts a variety of segregation, trapping and supersaturated solution studies.
Photoelectric Emission Studies from Crystalline Silicon at 266 Nm
Authors: Malvezzi A. M. , Liu J. M. , Bloembergen N.
Published: March 2011

Three different photoelectric regimes are observed in the interaction of 15 ps, 266 nm laser pulses with crystalline silicon samples versus light fluence. A superposition of linear and quadratic photoionization is followed by a space charge limited regime up to the critical fluence F4ωth for the surface amorphization where highly nonlinear ion emission is observed. Ion and electron emissions become equal in magnitude at a fluence - ∼ 2F4ωth The absence of observable thermionic effects indicates that thermal equilibrium of the electronhole plasma and the lattice is reached during the laser pulse duration.
Solidification of Highly Undercooled Silicon: Bulk Nucleation and Amorphous Phase Formation
Authors: Wood R. F. , Lowndes D. H. , Narayan J.
Published: March 2011

Recent experimental and theoretical work suggests that bulk nucleation occurs in highly undercooled liquid silicon formed by the pulsed laser melting of amorphous layers. In this paper we discuss the dynamics of solidification of undercooled liquid silicon in terms of results from melting model calculations and from the theory of homogeneous bulk nucleation. The relationship between the occurrence of bulk nucleation and the ability to induce a liquid-to-amorphous phase transition by large undercoolings of the liquid is considered. It is concluded that the observed liquid-toamorphous transition in silicon cannot be explained by an equilibrium thermodynamic approach.
Germanium Extremely Heavily Doped by Ion-Implantation and Laser Annealing: A Photoluminescence Study
Authors: Wagner J. , Contreras G. , Compaan A. , Cardona M. , Axmann A.
Published: March 2011

It has been shown previously that dopant concentrations far above the equilibrium solubility limit can be obtained in semiconductors by pulsed laser annealing of heavily ion implanted material. We exploit this fact to study the photoluminescence of germanium with dopant concentrations up to 1021 cm−3. From this study we obtain information on the filling of higher lying band minima and the shift of the optical band gap as a function of carrier concentration over a much wider range than accessible with bulk doped material. In addition it is shown that photoluminescence provides a diagnostic tool to characterize implanted layers.
Concentration-Independent Solute Segregation in Laser Annealing of Semiconductor Crystals
Authors: Chikawa Jun-ichi , Sato Fumio , Sunada Tadasu
Published: March 2011

Atomic processes at the interface in regrowth following laser induced melting were investigated by observing behavior of impurity segregation. The interfacial segregation coefficient k* was obtained from depth profiles of solute atoms redistributed by laser irradiation of uniformly doped Si, Ge, and GayAl1−yAs crystals. It was found that k*=k0 for B in Si, Ga in Ge ih the growth rate range of 1 m/s. It is concluded that rapid growth freezes a state of liquid monolayer adjacent to the interface which has the character of ideal solution from dilute to eutectic composition for dopant-silicon systems and in the entire range of composition for the mixed crystal.
Relaxation Behavior of Metastable As and P Concentrations in Si After Pulsed and CW Laser Annealing
Authors: Goetzlich J. , Tsien P.H. , Ryssel H.
Published: March 2011

Metastable solid solutions of arsenic and phosphorus atoms were created by high-dose ion implantation in silicon, followed by annealing either with pulsed (Nd:YAG) or CW (CO2;) laser irradiation. The relaxation of these supersaturated layers was investigated by thermal post-treatment at temperatures between 600 and 1000°C. By measuring the time dependence of the sheet carrier concentration, the time constant and the activation energies for the relaxation of the electrically-active As and P atoms were investigated. In addition, the equilibrium carrier concentrations at different temperatures were obtained by Halleffect measurements in connection with a layer-removal technique.
Structural and Electrical Properties of Gas immersion Laser Doped Layers in Crystalline Silicon
Authors: Sigmon T.W. , Carey P.G. , Press R.L. , Fahlen T.S. , Pressley R.J.
Published: March 2011

4 He backscattering and channeling and 4-point probe resistivity measurements are used to characterize the doping of 〈100〉 Si directly from the gas phase by using a laser induced melt/recrystallization process. Impurity concentrations from 3×1019 to 5×1020 cm−3 and sheet resistivities as low as 20 Ω/╒ are obtained by variation of the laser energy density or number of passes. Diodes fabricated by this process exhibit near ideal I-V characteristics with sharp reverse breakdowns determined by junction edge effects. Annealing at 850° C further reduces the generation-recombination centers to values that result in an ideality factor of 1.0.
Rapid Annealing of Silicon
Authors: Hodgson R. T. , Deline V. , Mader S. M. , Morehead F. F. , Gelpey J.
Published: March 2011

Silicon implanted with arsenic or boron has been annealed with a 100kW argon arc lamp turned on for a few seconds until the wafer temperature was in the 850–1250°C temperature range. The differences in defect behavior between such rapid annealing and furnace annealing is pointed out, and the dopant diffusion is measured. Aside from an initial movement of the boron atoms left in interstitial positions after the implant, diffusion of the boron and arsenic is consistent with standard diffusion models.
Transient Annealing of Boron Implanted Devices
Authors: Wilson S. R. , Paulson W. M. , Varker C. J. , Lowe A. , Gregory R. B. , Reuss R. H. , Wu S. Y. , Whitfield J. D.
Published: March 2011

Shallow-junction semiconductor devices have been fabricated using ion implantation and transient annealing with a Varian IA-200 isothermal annealer. Boron implanted diodes, npn bipolar transistors and CMOS ring oscillators have been fabricated and are compared to furnace annealed devices. Boron implanted diodes have been annealed with the RIA and yield acceptably low leakage currents, comparable to furnace annealed devices. The RIA devices have recombination lifetimes of ∼10 μsec. The bipolar transistors subjected to a transient anneal have good base-collector and emitterbase junctions as well as gains of ∼100 in good agreement with the design of the device. MOSFETs and CMOS ring oscillators were fabricated using self-aligned polysilicon gates. The transient annealed devices were equal or superior to devices which were furnace annealed at 800°C for 10 min. The low temperature furnace anneal was necessary to minimize short channel effects. The transient anneal resulted in ring oscillators which were a factor of two faster than furnace samples that were annealed.
Influence of Rapid Thermal Annealing on Shallow BF2 Implantation into Pre-Amorphized Silicon
Authors: Maszara W. , Carter C. , Sadana D. K. , Liu J. , Ozguz V. , Wortman J. , Rozgonyi G. A.
Published: March 2011

Low energy, shallow BF2+ implants were carried out at room or liquid nitrogen temperature into deep pre-amorphized (100) Si for better control of the dopant profile and post-annealing structural defects. Cross sectional and angle polished plan view transmission electron microscopy were used to study the structural quality of the implanted layer, while SIMS provided a chemical profile. Four types of structural defects were observed in BF2+ implanted, pre-amorphized samples following rapid thermal annealing with a halogen lamp. An in-situ ion beam annealing and the presence of F in the Si lattice were related to the creation of the defects. Good correlations between F gettering and TEM observed defects were found to exist. Implantation of B+ into a pre-amorphized Si surface and subsequent rapid thermal annealing was found to produce a wide defect-free surface layer.
Electron beam Annealing of Shallow BF2 Implantations
Authors: Jaussaud C. , Cartier A.M. , Escaron J.
Published: March 2011

A multiple scan electron beam system has been used to anneal silicon implanted with BF2 (25 Kev, 1, 2 and 5 × 1015 ions × cm−2 ). The annealing temperatures range from 1000 to 1200° C and the annealing times from 3 to 18 seconds. The curves of sheet resistance as a function of annealing time show a minimum. The increase in sheet resistance at longer annealing times is due to boron outdiffusion. Junction depths have been measured by spreading resistance and are presented. For implanted doses below 2 × 1015 ions × cm−2 boron outdiffusion limits the sheet resistance value at about 100 R Ωand this minimum value corresponds to an increase in junction depths of about 500 Å. For implanted doses of 5 × 1015 ions ×cm−2, 60 Ω sheet resistance can be obtained, but with about 1000 Å increase in junction depth.
CW Backside Laser Gettering
Authors: Hawkins Gilbert , Erikson George
Published: March 2011

A variety of backside damage techniques are available for gettering heavy-metal contaminants in silicon wafers. These include mechanical damage, ion implantation, thin film deposition, and pulsed–laser surface melting. In each case, strain fields and microscopic defects induced by the processing trap impurities as they diffuse through the wafer during subsequent high–temperature processing steps. We examine the defect structures produced by CW laser gettering, describe the dependence of gettering efficiency on wafer oxygen content and processing conditions, and demonstrate that CW laser processing can be an effective gettering technique even when the number of laser scan lines is reduced to make wafer processing acceptably rapid.
New Reliable Structure for High Temperature Measurement of Silicon Wafers Using a Specially Attached Thermocouple
Authors: Cohen S.A. , Sedgwick T.O. , Speidell J.L.
Published: March 2011

Accurate wafer temperature measurement is very important in the area of material processing. In Short Time Annealing, for example, it is necessary to monitor temperature peaks of up to 1200°C which are only a few seconds in duration. This paper describes a structure consisting of a silicon wafer with a specially attached thermocouple. This structure is capable of reliable high temperature measurements of up to 1200°C and is also capable of surviving repeated cycling at that temperature.
Rapid Thermal Annealing of Ion-Implanted Silicon and Gallium Arsenide
Authors: Narayan J.
Published: March 2011

We have investigated the annealing of ion implantation damage (in the form of amorphous layers and/or the layers containing only dislocation loops) in silicon and gallium arsenide. The annealing of amorphous layers occurs by solid-phase-epitaxial growth and that of dislocation loops involves primarily loop-coalescence as a result of conservative climb and glide processes. The annealing of disolated loops occurs primarily by a bulk diffusion process. Almost a “complete” annealing of displacement damage is possible for shallow implants provided loop–coalescence does not lead to the formation of cross–grid of dislocations. For deep implants, the free surface cannot provide an effective sink for defects as in the case of shallow implants. Dopant profiles can be controlled to less than 1000 Å in layers having good electrical properties. The enhanced diffusion of dopants is observed probably due to entrapment of point defects in the annealed regions.
Electronic Defects in Silicon after Transient Isothermal Annealing
Authors: Pensl G. , Schulz M. , Stolz P. , Johnson N.M. , Gibbons J.F. , Hoyt J.
Published: March 2011

We have investigated trap levels in silicon after Thermal Pulse Annealing (TPA). Three different annealing systems consisting of tungsten lamps or a graphite heater have been applied. Trap levels induced in different silicon materials (Cz, FZ, Epi) after TPA have been studied by DLTS and admittance spectroscopy. In boron-doped epitaxial silicon and As+- implanted pn-junctions (Cz grown Si), we have observed a prevalent trap level at concentrations of up to 1015cm−3 (depending on anneal conditions and silicon material). The ionization energy of this trap level is Ev+300meV.

The concentration of the 300 meV-level was studied as a function of the annealing temperature and the quench rate. The thermal pre-processing history strongly affects the trap concentration induced by TPA. The 300 meV-level is almost completely removed by a subsequent furnace anneal at TA > 400°C

Further trap levels are created in boron- and aluminum- doped silicon by Ar+ or 30Si+ implantation and TPA. The defect natures are discussed.
Crystal Growth and Solute Trapping
Authors: Aziz Michael J.
Published: March 2011

A simple model for solute trapping during rapid solidification is presented in terms of a single unknown parameter, the interfacial diffusivity Di. A transition from equilibrium segregation to complete solute trapping occurs over roughly an order of magnitude in growth speed, as the interface speed surpasses the maximum speed with which solute atoms can diffuse across the interface to remain ahead of the growing crystal. This diffusive speed is given by Di/λ, where λ is the interatomic spacing, and is typically of the order 10 meters per second. Comparison is made with experiment. The steady–state speed of a planar interface is predicted by calculating the free energy dissipated by irreversible processes at the interface and equating it to the available driving free energy. A solute drag term and an intrinsic interfacial mobility term are included in the dissipation calculations. Steady–state solutions are presented for Bi–doped Si during pulsed laser annealing.
Kinetic Competition During Solid Phase Crystallization in Ion–Implanted Silicon
Authors: Olson G.L. , Roth J.A. , Hess L.D. , Narayan J.
Published: March 2011

We report on an investigation of the temperature and concentration dependent kinetic competition between solid phase epitaxy and complex formation and precipitation in arsenic–implanted Si(100). Crystallization kinetics were monitored using time–resolved reflectivity during cw laser irradiation or furnace heating; microstructural changes were evaluated using cross–sectional TEM. At low temperatures and high As concentrations, complex formation and precipitation substantially alter the SPE kinetics. At higher temperatures competing interactions are less significant, and SPE becomes the dominant process. The kinetic competition between these processes is discussed with respect to the vacancy model for SPE.
Defect Reduction by Tilted Zone Crystallization of Patterned Silicon Films on Fused Silica
Authors: Fennell L. E. , Moyer M. D. , Biegelsen D. K. , Chiang A. , Johnson N. M.
Published: March 2011

It is well known that crystal growth and defect propagation occur along the local thermal gradient at a liquid - solid interface, It is shown here that this property can be used to greatly reduce the density of structural defects in zone crystallized silicon thin films on amorphous substrates, A solidification front perpendicular to the direction of zone motion has its in - plane component of the thermal gradient parallel to the direction of zone motion. In this case, the defects, once nucleated, propagate along this zone path and the defect density reaches a steady state value. By using striped polysilicon patterning and a solidification front tilted relative to the molten zone path, a defect-free region is shown to occur. It is also shown that defects, once nucleated, are swept laterally from the region of interest and are terminated at the stripe boundary Methods of forming a tilted interface are proposed and demonstrated for CO2 laser crystallization.
Large Area Subgrain-Boundary-Free Sot Induced by Thermal Gradient Control of Transitional Seeded-Growth
Authors: Lee El-Hang
Published: March 2011

ABSTRACT

The transitional region of subgrain-boundary-free crystal to subgrain-boundary-laced crystal formed during the initial stage of energy-beam induced seeded recrystallization of thin film silicon on an insulator has been examined to study the primary cause of subgrain boundary formation and the conceptual basis of its suppression. Observations include the systematic variation of: facet, cellular, and dendritic features; subgrain boundary directions and spacings; and the stable growth distance as a function of silicon film thickness and energy beam density. A temperature gradient argument based on constitutional supercooling theory has been used to explain these observations. There are indications that an increased thermal gradient at the solidification front can suppress the onset of growth instability for large area, defect free growth of SOI.
Two Dimensional Numerical Thermal Analysis of Silicon on Insulator Recrystallization Processes by a Moving Heat Source
Authors: Chang C.Y. , Fang Y.K. , Wu B.S. , Chen R.M.
Published: March 2011

The moving-zone melt recrystallization of polysilicon on insulator substrate has been studied with computer simulation methods. The most important parameters such as upper strip heater moving velocity, the power of upper strip heater, substrate temperature were investigated. Generally speaking, temperature profile in multilayer and melt depth of poly-Si are difficult to be visualized, but are still important for recrystallization process. Therefore by using two dimensional finite difference method, a numerical analysis of moving melt zone recrystallization processes has been developed. Through this analysis, the temperature profile in multilayer and melt depth of poly-Si are depicted.
Fentosecond Time Resolved Surface Structural Dynamics of Optically Excited Silicon
Authors: Shank C. V. , Yen R. , Hirlimann C.
Published: March 2011

Laser processing of materials has raised a number of interesting issues relating to phase transitions and the structure of optically excited semiconductors. In this paper we describe the dynamics of structural changes that take place on a silicon surface following excitation with an intense optical pulse. Second harmonic generation from the silicon surface is used as a tool to measure crystalline order with 90 femtosecond resolution. The three-fold rotational symmetry of the silicon <111> surface is observed to become rotationally isotropic within a picosecond after excitation consistent with a transition from the crystalline to the liquid molten state.
Line-Source E-Beam Crystallization of Silicon-on-Insulator Films
Authors: Knapp J. A. , Picraux S. T.
Published: March 2011

Silicon-on-insulator films have been formed using a 20 mm by 1 mm line-source electron beam, with sample sweep speeds of 100–500 cm/sec and peak beam power densities up to 75 kW/cm2. Films were formed over 1 and 2 μm thick SiO2 isolating layers on 4°C diameter Si<100> wafers, with stripe openings of 5 to 100 μ width for seeding the crystallization from the substrate. Films consisted of Si layers from 0.4 to 1.0 μm thickness, with a capping layer of 2 μm SiO2. By sweeping the beam parallel to the long axis of the seed openings, smooth, oriented films were obtained, with low-angle grain boundaries confined to midway between seed openings. Best results were obtained for ≲ 50 μm spacing between seed openings.
Three-Dimensional Integrated Circuit Technology
Authors: Antoniadis Dimitri A.
Published: March 2011

Within the last five years considerable research has focused on techniques to create “device-worthy” crystalline silicon films on insulators. Though several applications for such techniques have been proposed, none is more exciting than the prospect of “3-D Integration”, which has come to mean any IC technology that would yield more than one plane of active devices. This paper reviews the progress to date in this field by critically examining the merits and dismerits of the several silicon film preparation techniques, the several proposed 3-D device structures, and some possible applications of 3-D integration in electronic systems.
Laser Induced Synthesis of Compound Semiconductors
Authors: Laude L. D.
Published: March 2011

A review is given of a technique in which compound semiconductor films are produced by direct synthesis from multilayered, polymetallic films deposited onto insulating substrates and laser-irradiated in the CW or pulsed regime. Such films are characterized by a high degree of crystallinity together with optical and transport properties sufficiently close to single crystal ones to allow for various applications in optoelectronics.
Surface Temperatures and Dissociation Loss During the Pulsed Laser Annealing of GaAs
Authors: Pollock John T.A. , Rose Alex
Published: March 2011

From reported equilibrium partial and total dissociation pressure data for GaAs and melt times derived from reported time resolved reflectivity experiments, estimates have been made of the anticipated rate of As loss. Good agreement was found with experimentally determined As loss. A similar approach using experimentally determined Ga loss data allowed estimates of the maximum temperatures reached during pulsed laser annealing. These temperatures are considerably higher than suggested in thermal modelling studies. The boiling point of Ga gould be exceeded at incident laser energies >0.8 J cm−2.