bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigations on a New Failure Model for Electromigration
Authors: Kitchin J. , Lloyd J. R.
Published: March 2011

A new statistical model for electromigration failure in fine-line thin film conductors is developed in [1] by extending [2] to incorporate the statistics of microstructure and concomitant variations in the activation energy for grain boundary diffusion. The resulting distribution of time t to failure is well-approximated by

where N is the number of line segments that are potential independent failure elements, 1μ and σ are, respectively, the mean and standard deviation of an assumed normal distribution of activation energy in grain boundaries, γ is a scaling constant, T is in degrees Kelvin, j is the current density in the line, p1 is the fraction of line segments for which exactly one grain boundary occurs between two blocking boundaries, and Φ is the standard normal cumulative distribution function. (Note: .)
Shadow Step Structures for CV Dot Formation and Evaluation
Authors: Shah Nitin B. , Rosvold Warren C.
Published: March 2011

“Shadow Step Structures” (3S) [1] are pre-patterned mesa-type geometries which are electrically self-isolating when overlayed with conducting thin films. This structure has been successfully implemented to generate CV dot structures. This CV dot structure eliminates the need for screen or photomasking after the oxide growth, thus eliminating manual handling, poor definition of dots due to “shadow screens”, and eliminates the possibility of contamination from screens and/or chemicals. This technique is very useful to qualify metal coaters as opposed to conventional techniques which involve patterning after metal deposition and has the advantage of fast turnaround and inherent cost savings. Measurement fidelity has been demonstrated via a large statistical sampling and is shown to give CV results consistently more accurate and superior to CV structures generated using the conventional techniques of metal shadow screens or photo masking.
Oxidized Porous Silicon Moisture Sensors for Evaluation of Microelectronic Packaging
Authors: Kelly M. J. , Guilinger T. R. , Peterson D. W. , Tuck M. R. , Sweet J. N.
Published: March 2011

Accurate moisture measurements in microelectronic assemblies are crucial in assessing reliability of integrated circuits (ICs). We describe the fabrication and use of a silicon-based device for evaluation of moisture barrier coatings. The capacitive moisture sensors use oxidized porous silicon (OPS) as the sensing element. Porous silicon (PS) is formed by anodization of Si in hydrofluoric acid (HF). Oxidation of PS in oxygen produces OPS, which is also porous if an appropriate starting microstructure and oxidation treatment are selected. Metallization layers on the OPS and the wafer back complete the capacitor structure. The capacitance of OPS sensors is functionally related to the moisture content of the surrounding atmosphere. For example, the capacitance of one sensor changed from 4 nF/cm2when exposed to a moisture level of 300 ppm by volume (ppmv) to 36 nF/cm2at 10,000 ppmv. In addition to this excellent sensitivity, capacitor response to step changes in moisture is rapid and reversible. The sensors are also rugged, as demonstrated by their consistent performance during accelerated testing at 85% relative humidity and 140°C. A silicon nitride IC moisture barrier coating was deposited on sensors of this type after normal ceramic dual in-line packaging. Sensor operability after coating deposition was confirmed following intentional introduction of a pinhole into the moisture barrier coating.
A Technique for the Examination of Surface Effects in Aluminum Nitride Ceramics
Authors: Norton M. Grant , McKernan Stuart , Carter C. Barry
Published: March 2011

A specimen preparation technique for the study of surface reactions and thin-film effects in aluminum nitride ceramic substrates is described. The technique uses specially prepared electron-transparent thin-foil substrates. These substrates can be examined directly in the electron microscope without the need for any further specimen preparation.
Electromigration Behavior in Layered Ti/AlCu/Ti Films and its Dependence on Intermetallic Structure
Authors: Rodbell K. P. , DeHaven P. W. , Mis J. D.
Published: March 2011

A sputtered aluminum-low copper (Cu concentration < 2wt.%Cu), multilayered, submicron, device interconnect metallurgy consisting of two TiAl3 layers (∼,0.1μm thick) under and over an Al-Cu alloy conductor (0.95μm thick) with either an Al-Cu or TiN cap layer (0.05μm thick) has been developed. These films were patterned by reactive ion etching, and showed both a low susceptibility to corrosion and a low resistivity. Electromigration lifetime data on Al, Al-Cu, and both dc magnetron sputtered and electron gun evaporated multilayered fine lines, fabricated and tested in the same laboratory, are included for a direct comparison. Outstanding electromigration behavior was measured for sputtered, multilayered, submicron films with copper concentrations between 0.12 – 2wt.%Cu. In contrast, electromigration lifetimes of evaporated, multilayered films were found to degrade rapidly at < 2wt.%Cu. This anomalous electromigration behavior was attributed to structural differences in the Ti-Al intermetallics formed. It is proposed that defects present in the Ti-Al superlattice phase cause decreased electromigration performance compared to films in which TiAl3 exclusively forms. Multilevel structures, consisting of CVD W interlevel vias, were also investigated and found to have significantly degraded electromigration performance compared to planar samples. This was attributed to geometric and material flux divergences at the via/conductor interfaces.
The Effects of Stress on the Interdiffusion in Si1-xGex/Si Superlattices
Authors: Prokes S.M.
Published: March 2011

The effects of grown-in stress and applied external stress on the interdiffusion behavior in long-period Si0.7Ge0.3/Si is examined using x-ray diffraction and Raman Spectroscopy. Both symmetrically and asymmetrically–strained superlattices have been examined, and an activation energy for interdiffusion of 3.9 eV and 4.6eV have been obtained, respectively. In addition, an enhanced interdiffusion has also been measured when the asymmetrically–strained superlattice was subjected to an external tensile stress during annealing. In both cases, enhanced interdiffusion has been measured whenever the Si barrier layers experience tensile stress during annealing. The Raman results indicate that enhanced Ge diffusion into the Si barriers occur when these barriers are put under tensile stress. This result will be discussed in terms of the kinetics of defect formation and motion in the strained Si barriers.
Crystal Plasticity Analysis of Thermal Deformation and Dislocation Accumulation in Gaas/Si Patterned Structure
Authors: Ohashi Tetsuya , Honda Naoyuki
Published: March 2011

Plastic slip deformation in patterned.GaAs films on Si substrate during cooling from film deposition temperature are numerically simulated under a continuum mechanics approximation. The plastic slip is assumed to take place on (111) <110> slip systems and activation condition of the slip systems is given by the Schmid's law. The critical resolved shear stresses for the activation of slip systems are expressed as a function of accumulated dislocation densities, which are evaluated by models for their movement and interaction. A three dimensional finite element computer program is developed, in which strain hardening behaviour is given a quantitative expression by the models for dislocations. Results of the simulation reveal process of plastic slip and dislocation accumulation in GaAs film. Residual stress evaluated by the simulation agreed well with results obtained by photo-luminescent experiments.
Stress in Metal Foils During Processing and Thermal Cycling.
Authors: Jagota A. , Lemon M.F. , Hu Y.H.
Published: March 2011

The vibrational technique for stress measurement in films has been used to study silver foils, silver-based conductor pastes, and aluminum foil. During cooling, a tensile stress develops in the films due to thermal expansion mismatch with the substrate. Because the stress is limited by the yield stress, these experiments furnish data for the yield stress of the materials over a wide range of temperature at fixed state. Experiments with silver specimens pre-annealed to different grain sizes show that the yield stress follows the Hall-Petch relationship. The full vibrational analysis is used to extract the stiffness of the foils.
Growth and Microstructure of Aluminum Nitride Thin Films
Authors: Norton M. Grant , Kotula Paul G. , Li Jian , Mckernan Stuart , Cracknell Kathryn P.B. , Carter C. Barry , Mayer James W.
Published: March 2011

The synthesis of aluminum nitride thin films by pulsed-laser ablation is demonstrated. The films were formed on single-crystal sapphire and graphite substrates. A number of techniques were used to characterize the films: transmission and scanning electron microscopy, Rutherford backscattering spectrometry and x-ray diffraction.
Relaxation of Thermal Stresses in Al-Films
Authors: Bohn H.G. , Pill W. , Robrock K.-H , Schilling W.
Published: March 2011

The time and temperature dependent mechanisms underlying the relaxation of thermally induced stresses in Al-films on quartz substrates have been investigated for film thicknesses in the range between 0.4 and 4.2 μm. Film stresses were determined by a high resolution capacitive technique from the bending displacement of the specimens. By employing a lamp furnace heating rates of 10°C/sec could be achieved. This test equipment allowed the investigation of thermally induced film stresses between room temperature and 450°C and in the time range between 10 sec and several hours. Similar temperature programms were run in situ in a scanning electron microscope in order to observe the concommitant changes of the surface morphologies.

The experiments show that a major fraction of 50 to 70% of the thermal stress recovers instantaneously by plastic flow. This defines a yield stress for the Al-films which is found to be inversely proportional to the film thickness and to vary linearly with temperature. The magnitude of the yield strength under tension is larger by a factor 1.7 compared to that under compression.
Fracture Behavior of Silicon Cut with a High Power Laser
Authors: Chao C.C. , Chleboski R. , Henderson E.J. , Holmes C.K. , Kalejs J.P. , Gross T.S.
Published: March 2011

The fracture twist test is used to obtain the statistical fracture strength distribution for 10-cm square single crystal and polycrystalline silicon wafers cut with a high-power Nd:YAG laser. Tensile wafer edge stresses at fracture are calculated using nonlinear finite element analysis, and the model results are used to examine the limitations of linear torsion and plate theories. The basic hypothesis is that fracture strength of laser-cut wafers is limited by microcracks formed by large residual tensile stresses produced in the cut edge upon cooling after cutting. Differences are found between single crystal CZ and polycrystalline EFG silicon material Weibull parameters characterizing the fracture strength distribution. These indicate that there is a statistical influence of material variables on the fracture strength of the EFG silicon, which lowers its strength and increases the variance of fracture response in comparison to single crystal silicon.
The Singular Behavior of the Lattice Hardness of Bismuth Cuprates Under Thermocycling
Authors: Belomestnykh V.N. , Khasanov O.L. , Pokholkov Yu.P. , Bush A.A.
Published: March 2011

Temperature depepdences of ultrasound velocity V and sound attenuation Q−1,the unit cell parameters a, b, c, and volume W were studied between 77 and 800 K for bismuth cuprates like Bi2Sr2Can−1 CUnO2n+2+8 with n = 1,2,3 (phases: 2201, 2212, and 2223). Acoustic spectra of textured and isotropic samples show anomalies (bending points,extrema, breaks, and splitting of resonance frequency) which are considered as a result of thermostimulated processes - phase transitions of I and II kinds, emergence of substructures in the cuprate lattices - in a system of solid solutions of the mentioned phases. Mechanical properties of the studied systems are observed to be very sensitive to a thermal prehistory (temperature and time ranges of thermocycling).
Testing of Fracture Resistance of Materials
Authors: Ni Beta Y. , Zhang T. Y. , Li J. C. M.
Published: March 2011

Both energy and load required to fracture the material are important quantities and they are not necessarily related to each other as suggested by the fracture mechanics of brittle materials. For example, the difference of the failure behavior between the semi-brittle ABS polymer and the ductile Al 6061-TO can be well characterized by a pre-fracture energy E0 (Joule/m) and a fracture energy Ef (Joule/m2 ). Al 6061-TO has much higher values of E0 and EF than the ABS polymer. This accounts for the ductility of Al 6061-TO. However, the applied stress intensity factor KIapp for both materials are similar. The reason is that their plastic zones have similar shielding effects, even though Aluminum has dislocations and the ABS polymer has cavities and crazes.
The Effect of A Passivation Over-Layer on the Mechanisms of Stress Relaxation in Continuous Films and Narrow Lines of Aluminum
Authors: Paszkiet C. A. , Korhonen M. A. , Li Che-Yu
Published: March 2011

Stress relaxation was studied in bare and nitride-covered continuous films and narrow lines of aluminum. The rate of relaxation in unpassivated metallizations is shown to be consistent with a dislocation-controlled mechanism. Relaxation in passivated lines appears to depend on grain boundary diffusion-controlled void growth. In passivated continuous films, two rate-controlling mechanisms appear to operate in sequence.
Real-Time FT-IR Studies Of The Reaction Kinetics For The Polymerization Of Divinyl Siloxane Bis-Benzocyclobutene Monomers
Authors: Stokich T. M. , Lee W. M. , Peters R. A.
Published: March 2011

The thermal polymerization reaction of divinyl siloxane bis-benzocyclobutene (DVS bis-BCB) was monitored in-situ with FT-IR spectroscopy in order to follow specific chemical changes and determine the reaction order and rate constants at temperatures from 150° to 210°C. FT-IR spectra were obtained at regular intervals throughout the reaction with a Nicolet 170SX spectrophotometer.

Monomeric DVS bis-BCB contains mixed stereo and positional isomers of 1,3- bis(2-bicyclo[4.2.0]octa-1, 3, 5-trien-3-ylethenyl)-1, 1, 3, 3-tetramethyl disiloxane (CAS 117732-87-3). It polymerizes via Diels-Alder cycloaddition reactions between vinyl groups and an intermediate o-quinodimethane formed by first-order, thermally initiated ring openings of the benzocyclobutene rings. Gaseous byproducts are not produced; therefore, the cure is easier to manage than are cures for polyimides which evolve water in polycondensation reactions. The DVS bis-BCB has four reactive elements per monomer unit and, thus, polymerizes into a very highly cross linked and solvent resistant network.

With the FT-IR methodology, the reaction was easily monitored through the points of gel formation and vitrification. With the exception of DSC (i.e., calorimetry) which does not sense specific chemistry, other methods were not successful in following the reaction after a gel was formed. We have found that the polymerization was first-order until vitrification occurs; the gelation alone had no apparent effect on the reaction rate.

DVS bis-BCB is under development at Dow as high performance dielectric material for multilayer interconnect coating applications for the microelectronics industry. Methodology reported here is employed in developing effective cure management strategies.
CT Fluorescence And Molecular Aggregation Of A Polyimide As Function Of Imidization Condition.
Authors: Hasegawa M. , Arai H. , Horie K. , Yokota R. , Mita I.
Published: March 2011

The emission mechanisms of solid PI(BPDA/PDA) derived from biphenyltetracarboxylic dianhydride (BPDA) and p-phenylenediamine (PDA) were examined with the absorption and fluorescence. spectra of model compounds (denoted by M). M(BPDA/CHA) (CHA: cyclohexyl amine) fluoresces at ca. 430 nm in hexafluoro-2-propanol(HFP) solution, while M(BPDA/AN) (AN: aniline) does not. PI(BPDA/PDA) film does not show the monomer fluorescence of biphenyldiimide unit, but shows only intermolecular CT fluorescence peaking at 530–540 nm. This suggests that for PI(BPDA/PDA) film and PI(BPDA/AN) in solution the local excited state of biphenyldiimide units is deactivated owing to intramolecular charge-transfer(CT).

The intermolecular CT fluorescence reflecting sensitively molecular packing of PI chains was used to monitor isothermal imidization process of poly(amic acid)(PAA) of BPDA/PDA. The fluorescence of PAA(BPDA/PDA) peaking at 490 nm decreases rapidly and disappears at 30–40% conversion, then the fluorescence of PI(BPDA/PDA) peaking at 540 nm increases gradually during isothermal imidization. The fluorescence intensity at 540 nm increases rapidly as imidization proceeds when imidized at higher temperature. A kinetic study on isothermal imidization shows that the vitrification is strongly related to the reorientation of polymer chains and the final PI structures.
Bismaleimide/Allylnadic-Imide Blends Yield Low Dielectric Constant And Low Water Uptake
Authors: Ansermet J-PH , Kramer A.
Published: March 2011

The bismaleimide resin Matrimid 5292A (I) was cocured with an allylnadic-imide resin (EP 433) which contained a long aliphatic chain as backbone (II). Water uptake, swelling, and the dielectric properties (up to 300 MHz) were studied in cast plates. The dielectric constant varied from 5.4 in (I) to 3.2 in (II) at water saturation, compared to 3.1 in (I) to 2.7 in (II) in the dry state. The glass transition temperature stayed above 200 °C at less than 80 mol% of (II).
Characterization Of The Binding of Inorganic Polymers To Oxide Surfaces By NMR and NMR/MAS Spectroscopy
Authors: Burton Sarah D. , Samuels William D. , Exarhos Gregory J. , Linehan John C.
Published: March 2011

Solution and solid state Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR) spectroscopy have been used to monitor the 31P signal of cyclic phosphazenes and associated linear polymers in solution and of these materials bound to alumina in stabilized dispersions. The differences between the simple solution experiments and the suspensions are being studied to determine the viability of NMR techniques to probe the chemical interactions between inorganic polymer dispersants and alumina particles. It has been observed in colloidal suspensions that the adsorption of phosphazenes onto an aluminum oxide surface causes a broadening of the 31P signal in solution NMR. This broadening is dependant on the amount of solid to polymer concentration, the amount of solids loading, the solvent polarity and the phosphazene substituent under investigation [1]. Conversely, the solid MAS experiments show a narrowing of the 31P signal upon adsorption of the phosphazene to alumina.
The Determination Of The Residual Stress State And Its Effect On Peel Tests In Polyimide Coatings.
Authors: Farris Richard J. , Maden Michele A. , Goldfarb Jay , Tong Kun
Published: March 2011

The determination of residual stresses in thin polymer coatings is crucial in the prediction of failure due to delamination and cracking. This is especially important in the electronics industry where thin polymer dielectric layers are used. The dielectric layers are often under three-dimensional constraints and have holes through which metal interconnects run. These act as locations of high stress concentration. Three complementary methods have been developed which will provide a better base for understanding the delamination and performance of thin coatings.

These techniques include, a holographic interferometry method for determining the residual stresses in coatings (˜10 μm thick); a deformation calorimetry technique for establishing an energy balance for peel tests; a set of experiments for measuring the nine elasticity coefficients for orthotropic films. The combination of these methods allows a comparison between the residual stresses present in coatings and the contribution of those residual stresses to the work needed for peeling. The knowledge of the stress state and elasticity coefficients is essential for determining the elastic energy in a coating. The total elastic energy which can be stored in a stressed coating increases with the coating thickness. Stressed coatings exceeding a critical thickness will spontaneously delaminate if the elastic energy in the coating is greater than the energy required for debonding. The elastic energy in the coating per unit area at the critical thickness is a measure of the interfacial strength.
Changes In The Characteristics Of The Free Volume Of Glassy Polymers During Deformation And Relaxation.
Authors: Tsapovestsky M.I. , Lavrentiev V.K. , Tishin S.A.
Published: March 2011

The behavior of glassy polymers was studied with the aid of mechanical tests on the basis of free volume. Three types of experiments were carried out and interpreted using modern ideas about the structure of free volume. They were: 1. The study of changes in the total free volume occurring as a result of deformation (by measurement of density) 2. The study of micro voids and their changes on deformation using small angle X-ray scattering (SAXS) and positron annihilation 3. The study of mobile regions by the measurement of dielectric loss (using an original interpretation) during deformation. This allows several parts of the total free volume to be distinguished and investigated. A model for the free volume relaxation during deformation is proposed.
Dielectric Relaxation Of Semicrystalline Polyimides
Authors: Huo Pengtao , Friler Jerome , Cebe Peggy
Published: March 2011

Aromatic polyimides because of their structure process a unique property combination of outstanding thermal stability and radiation and solvent resistance. Their excellent mechanical and electrical properties make polyimides the materials of choice for a wide range of applications in the electronics industry. Polyimides have long been amorphous materials but recently, flexible hinge groups containing ether and ketone linkages have been incorporated into the polymer backbone [1]. This results in increased flexibility and development of crystallinity. The introduction of crystallinity is an effective means of improving the melt processability, however, little work has been done to determine the effects of crystallinity on the insulating characteristics of polyimides. Here we report the dielectric behavior for the semicrystalline polyimide New-TPI [2], which is synthesized by Mitsui Toatsu Chemical Co. and film processed by Foster-Miller, Inc. We have used dielectric relaxation to study New-TPI, especially its behavior near Tg.
UV-Laser Photoablation Of Thermostable Polymers: Polyimides, Polyphenylquinoxaline and Teflon AF
Authors: Lazare Sylvain , Hiraoka Hiroyuki , Cros Alain , Gustiniani Régis
Published: March 2011

The UV laser ablation of three thermostable polymers, polyimide, polyphenylquinoxaline and Teflon AF of interest for microelectronics is presented. Direct absorption of the laser beam is not possible by Teflon, but a doping technique is described.
Adhesion Of Copper To Polytetrafluoroethylene Polymer Film With Adhesive Layers
Authors: Chan Chin-Jong , Chang Chin-An , Farrel Curtis E.
Published: March 2011

Enhanccd adhesion of Copper to spin-coated polytetrafluoroethylene PTFE.) film is achieved by employing an intermediate adhesive layer consisting of fluorinated ethylenepropylene (FEP) and metallic titanium. The peel strength of Cu on PTFE is low (1–2 g/mm) without the adhesive layer. After incorporating the Ti/FEP adhesive layer, a peel strength as high as 80 g/mm can be achieved. The overall peel strength is found to increase with the adhesive layer thickness. Thermal annealing at high temperatures strongly affects its overall peel strength. Previous XPS study indicated the formation of TiCx at the Ti/FEP and Ti/PTFE interfaces. Rutherford backscattering spectrometry and cross-sectional transmission electron microscopy studies revealed that significant amount of Cu diffused into the FEP layer through the Ti layer when the specimens were heat treated at 375°C for various amount of time. Cu diffusion strongly affects the interfacial properties and hence results in the variation of overall peel strength. The results indicate that the thickness of Ti barrier as well as the heat treatment temperature are important for retaining the high peel strength.
Stiff Polyimides: Chain Orientation And Anisotropy Of The Optical And Dielectric Properties Of Thin Films
Authors: Boese D. , Herminghaus S. , Yoon D. Y. , Swalen J. D. , Rabolt J. F.
Published: March 2011

Thin films of poly(p-phenylene biphenyltetracarboximide), prepared by thermal imidization of the precursor poly(amic acid) on substrates, have been investigated by optical waveguide, UV-visible, infrared (IR), and dielectric spectroscopies. The polyimide films exhibit an extraordinarily large anisotropy in the refractive indices with the in-plane index n║ = 1.852 and the out-of-plane index n┴ = 1.612 at 632.8 nm wavelength, indicating a strong preference of polymer chains to orient along the film plane. No discernible effect of the film thickness on this optical anisotropy is found in the range of ca. 0.4 μm to 7.8 μm in thickness. The frequency dispersion of the in-plane refractive index to 1.06 μm wavelength is consistent with the results calculated by the Lorentz-Lorenz equation from the UV-visible spectrum. The contribution from the entire IR range from 7000 to 200 cm,−1 computed by the Spitzer-Kleinmann dispersion relations from the measured spectra, adds ca. 0.07 to the in-plane refractive index n║. Approximately the same increase is assumed for the out-of-plane index n┴, based on the tilt-angle dependent IR results. Application of the Maxwell relation leads to the out-of-plane dielectric constant ε┴≃2.8 at ca. 1013 Hz, as compared with the measured value of ca. 3.0 at 106 Hz. Assuming this small difference to remain the same for the in-plane dielectric constants ε║, we obtain a a very large anisotropy in the dielectric properties of these polyimide films with the estimated in-plane dielectric constant ε║≃3.5 at ca. 1013 Hz, and ε.≃3.7 at 106 Hz.
Preparation And Characterization Of Thermoplastic/Thermosetting Polyimide Blends
Authors: Yamamoto Y. , Toyoshima T. , Etoh S.
Published: March 2011

Three kinds of thermoplastic/thermosetting polyimide blends have been prepared using three kinds of commercially available soluble polyimides(AL1051, PI2080, Ultem) and N, N′ – (methylenedi-p-phenylene) bismaleimide(BMI). The DSC thermograms of the polyimide blends showed exotherms at higher temperatures compared to BMI alone. The cure characteristics of the blends changed significantly according to the thermoplastic polyimide component. The fracture surfaces of PI2080 and Ultem blends, examined under a scanning electron microscope, showed distinct nodular morphological features. However, in the case of AL1051, which was derived from a aliphatic acid, this kind of phase separation was not observed. The mechanical properties of the blends were studied by using a thermomechanical analyzer. The blends yielded films with good mechanical properties even at high temperatures. The BMI component did not have any significant effect on the glass transition temperatures. However it showed improved mechanical properties at high temperatures. The blends were brittle compared with the thermoplastic polyimides. The tensile and electrical properties of the blends and their coefficients of thermal expansion were also studied.
Optical Waveguiding in Poled NLO Polymers
Authors: Swalen J. D. , Fleming W. , Jurich M. , Moerner W. E. , Smith B. A. , Herminghaus S. , Bjorklund G. C.
Published: March 2011

For potential optoelectronic applications, new polymeric thin films
containing nonlinear optical chromophores aligned by electric field poling
for a χ(2) nonlinear optical response have been prepared and
studied. Spectroscopic and optical waveguiding techniques, as well as second
harmonic generation and electrooptic measurements, are being used to
characterize these thin film materials. Here we optimize the chromophores in
spectral response, nonlinearity, concentration and degree of alignment.
Stability in the nonlinearity has been improved considerably by attaching
the chromophores to crosslinked epoxy polymers. Some applications of these
materials for electrooptic phase modulators will be presented.
Electrooptic Coefficients in Electric Field Poled Polymer
Waveguides
Authors: Smith Barton A. , Herminghaus S. , Swalen J. D.
Published: March 2011

Planar wavcguides were made from a linear epoxy copolymer of bisphcnol-A
diglycidyl ether and amino-nitro-tolanc. The refractive indices, ni-M and
n-E, and the clectrooptic coeflicients, r33 and r13,
of the poled nonlinear optical polymcr films were determined by measurements
of the wavcguide modes of these films at a wavelength of 632.8nm, and the
results arc reported for both electrode and corona poling. The ratio of the
second order susceptibilities was found to exceed significantly the
theoretically expected value of 3. Restricted motion of the nonlinear
chromophorcs during poling provides a possible explanation of this
discrepancy.
Nonlinear Optical Response of Nematic Droplets
Authors: Risser Steven M. , Ferris Kim F.
Published: March 2011

We have used a finite element method to calculate the nonlinear polarization
of small nematic droplets, for both the radial and bipolar director
configurations. The nonlinear polarization of droplets with a radial
director is concentrated along the droplet axis, while for the bipolar
droplets, the nonlinear polarization is more uniform across the droplet. The
nonlinear polarization of the bipolar configuration has also been shown to
be sensitive to the angle between the droplet axis and the applied
field.
Photorefractive Nonlinear Optics
Authors: Feinberg Jack
Published: March 2011

Photorefractive crystals are great for image processing, beam amplification,
and phase conjugation. I will describe these and a number of other new
applications of photorefractive crystals. I will also show how light beams
in these crystals are like politicians: if given the chance they will always
choose the path that maximizes their own gain.
Optical Information Processing with Quantum Well Seed's
Authors: Chirovsky Leo M. F.
Published: March 2011

This is a review of how and why modem epilayer growth techniques have led to a novel class of optical devices, the Quantum Well SEED's, and of how and why these devices, in turn, have enabled experiments on novel system architectures in which digital information is processed or routed in parallel optically, to take advantage of the large space-bandwidth product of free-space optical interconnects.
Highly Strained (InAs)M/(GaAs)N Multiple
Quantum Well Based Resonant Tunneling Diodes on GaAs (100) Substrates and
Their Application in Optical Switching
Authors: Kapre R. M. , Hu Kezhong , Chen Li , Guha S. , Madhukar A.
Published: March 2011

We report the realization of (a) an optically bistable switch using a
strained resonant tunneling diode (RTD) and (b) highly strained RTDs
exhibiting simultaneously high peak current densities (Jp) and
peak-to-valley current ratios (PVR) suitable for high-speed electronic
switching. Both of these make use of RTDs with
(InAs)M/(GaAs)N strained short period multiple
quantum well regions with AlAs barriers in a triple-well, double barrier
structure. For the former, high contrast ratio (20:1) and an on state
reflectivity of 46.5 % has been obtained at room temperature in an optically
bistable switch involving a strained InGaAs/GaAs (100) multiple quantum well
based asymmetric Fabty-Perot reflection modulator, detector, and a strained
RTD and a Si field effect transistor. For the latter, we have obtained a
Jp of 125 kA/cm2 with a PVR of 4.7 at room
temperature.
Epitaxial Structures For Optical Information Processing
Applications: Superlattice Infrared Detectors
Authors: Asom Moses T.
Published: March 2011

Advances in epitaxial growth techniques such as molecular beam epitaxy and
metal organic chemical vapor deposition have facilitated the formation of
high quality III-V heterostructures with dimensional control down to atomic
levels, with abrupt doping and near-defect-free interfaces. The flexibility
and remarkable control offered by these techniques have resulted in the
fabrication of new devices based on confinement or modulation of carriers in
thin III-V heterostructures. Quantum wells and superlattice based devices
are expected to be utilized in optical information processing as sources,
modulators, and detectors. In this paper, we will review the general
epitaxial requirements for quantum wells and superlattices based devices,
and discuss the fabrication and properties of a new class of infrared
photodetectors that employ intraband transitions in quantum wells.
Buried Concentration Profiles for Optical Waveguides by One-Step
Electro-Diffusion Process: Theoretical Analysis
Authors: Li Xiaoming , Johnson Paul F.
Published: March 2011

Introduction

In recent years, a two-step electric field assisted diffusion or
ion-exchange technique has been extensively studied for producing buried
concentration profiles in glass [1,2,3], polymer [4,5], electrooptic and
semiconducting [6,7] substrate materials to fabricate buried optical
waveguide devices. The technique contains two separate diffusion processes
and is quite complicated, cost and time consuming. In addition, theoretical
analysis of the technique is too complicated to be used for calculating and
tailoring concentration profiles. Many efforts have been made to pursue a
one-step process for producing buried profiles. Very recently, a novel
one-step technique [8] involving electric field assisted diffusion of silver
ions into glass from molten AgNO3 bath with decaying silver
concentration has been developed to produce buried Ag+
concentration profiles in glass substrate. The new technique is, from the
practical operation point of view, relatively simple and is a significant
improvement over the conventional two-step process.
Homoepitaxial Growth of p-Type ZnSe Layers on Dry-Etched
Substrates
Authors: Ohkawa K. , Mitsuyu T.
Published: March 2011

We have succeeded in the growth of p-type ZnSe homoepitaxial layers. The
layers have been grown by molecular beam epitaxy (MBE) on (100) ZnSe
substrates dry-etched with BCI3 plasma to eliminate polishing
damage. Nitrogen acceptors were incorporated by nitrogen radical doping
during MBE growth. Hall measurement by using Pt electrodes have indicated
that the N-doped ZnSe homoepitaxial layers are p-type with typical hole
concentration of 8.9×1015 cm−3. 12-K photoluminescence
(PL) from the layers exhibited strong neutral-acceptor-bound exciton
emission (11) at 2.7931 eV, indicating the peak energy of
11 emission from the strain-free ZnSe:N.
The X-Ray Spectral Microinvestigation of the Chinical States of
Atoms in CdxHg1-x Te/GaAs Thin Fiit.
Authors: Rezvitskii V. V. , Treicer B. A. , Bondarenko I. I. , Volkov L. A. , Mazalov L. N.
Published: March 2011

The results of the x-ray spectral investigations of
CdxHg1-xTe/GaAs thin films conducted with the help
of “Camebax - microbeam” electron microprobe are presented. It is shown that
the sensitivity of the microprobe combined with the mathematical processing
based on the chemometric approaches Is sufficient to reveal the effects of
the chemical bond on x-ray spectra.
Real Time Probes of Dye Doped Polymer Systems
Authors: Halpern J. B. , Amuzu-Williams P. , House L. , Lee L. A.
Published: March 2011

Recently, advanced photonic devices have been fabricated in the laboratory
and are becoming commercially available. Thus, there is considerable
interest in inexpensive but efficient non-linear optical (NLO) materials
that are simple to make and work with. In the last three years a large
number of publications and patents have appeared describing NLO properties
of organic materials, usually dyes, incorporated into or synthetically
attached to polymers [1]. Such materials must be oriented before they have
second-order NLO activity. Two methods have been used. In one, contact
poling [2–5], two electrodes are formed on or in the material and an
electric field is placed between them. In the other, corona poling, a
discharge deposits charge on the polymer, which creates a strong orienting
field [6–8]. One could generalize that contact poling is (more) difficult to
do, but the results are easy to understand, while corona poling is simple to
do, but the results are (more) difficult to understand. This paper describes
a set of corona poling experiments.
Highly Sensitive Absorption Measurements in Organic Thin Films:
Charge Transfer Complexes and Light-Induced Changes
Authors: Skumanich Andrew
Published: March 2011

Using the sensitive absorption technique of Photothermal Deflection
Spectroscopy (PI1S) it is possible to detect subtle spectral features in the
absorption spectra of polymeric thin films that cannot be detected by other
means. This paper describes observations of weak charge-transfer complex
(CIC) formation and also light-induced changes in various organic films. The
filns studied were those commonly used as charge transport materials in
organic photoconductors, comprised of a small transport molecule and a
polymer binder. The optically measured CTC bands can be used to establish
single electron energy levels of the constituents. Reproducible
photo-induced changes are manifest both in the strong UV transitions as well
as in the “sub-gap” absorption and appear to be correlated with the
photo-chemical stability of the constituents. The light-fatigue has both a
reversible as well as irreversible component.
The Measurement of Thermal Conductivity of Ag/Al Multilayered Films
Authors: Kaizuka Takeshi , Soe We-Hyo , Yamamoto Ryoichi , Ohyama Masanori
Published: March 2011

The in-plane thermal conductivity of Ag/Al multilayered films was measured at room temperature by ac calorimetric method as a function of the modulation wavelength and was compared with the electrical conductivity. The electrical conductivity increases with wavelength, Λ, like other metallic multilayered films. The thermal conductivity also tends to increase with Λ, but the Λ dependence is not similar to that of electrical conductivity. Obtained Lorentz number value of the multilayers are almost 10–30% larger than that given by the free electron theory. The Wiedemann-Franz law did not hold in the Ag/Al films and the phonon contribution is not negligible.
Hrem Investigation of the Structure of the Σ5(210)/[001] Symmetric Tilt Grain Boundaries in Nb.
Authors: Campbell G. H. , Foiles S. M. , King Wayne E. , Rühle M. , Wien W.
Published: March 2011

We have simulated the atomic structures of the Σ 5 (210)/[001 ] symmetric tilt grain boundary using interatomic potentials for Nb developed employing the embedded atom method (EAM) and the model generalized pseudopotential theory (MGPT). These potentials do not predict the same lowest energy structure for the Σ 5 (210)/[001]. Using the ultra high vacuum diffusion bonding process, we have fabricated Σ 5 (210)/[001] bicrystals. The samples have been observed using high resolution electron microscopy and the observed images have been compared with those simulated based on the structures predicted theoretically. The experimental result for the Σ 5 (210)/[001] is in close agreement with the structure predicted using the EAM.
Grain Boundary Structure and Structure-Behavior Relationships in HCP Metals
Authors: King A. H.
Published: March 2011

We present calculations of dislocation spacing for grain boundaries in zinc, and show that the spacings may be large enough to be resolved in conventional transmission electron microscopy even at extreme deviations from ideal coincidence misorientations. This effect is a result of the need for the dislocation arrays to accommodate slight differences between the ideal and actual axial ratios in addition to the difference between the ideal and actual misorientations. Recent observations of sliding behavior as a function of misorientation may also be rationalized within the framework of our structure calculations.
Anomaly in the Hall Ooefficient of Ag/Cr Superlattices
Authors: Sato Hideyuki , Kumano Tadashi , Kaneko Takeo , Yamamoto Ryoichi
Published: March 2011

The Hall effect on Ag/Cr superlattice system has been investigated. When the Cr layer thickness is changed from 1 monolayer (ML) to 6ML for the same Ag layer thickness of 10 ML, the Hall coefficient (RH) varies anomalously. For 1 ML Cr sample, we obtained RH value close to that of pure Ag as expected. The absolute value of RH is enhanced with increasing Cr layer thickness. After having a negative peak near 3 ML Cr, it decreases at larger Cr thicknesses. The field dependence of the Hall resistivity is linear for all the samples, and there is no sign of long range magnetic order down to 1.5K.
X-Ray Photoelectron and Auger Electron Forward-Scattering Studies of the Epitaxial Growth of Fe on Ag(100).
Authors: Egelhoff William F.
Published: March 2011

A controversy has arisen in the past year over whether or not the growth of Fe on Ag(100) at room temperature occurs by a layer-by-layer mechanism. The present work attempts to address this controversy with an investigation of the issues, primarily by x-ray photoelectron (XPS) and Auger electron forward scattering, but with important supporting data from low-energy electron diffraction (LEED), and reflection high-energy electron diffraction (RHEED) oscillations. The results of this work suggest that the origin of the controversy lies in different substrate preparation techniques which produce different atomic step densities on the Ag(100) surface. The step sites are implicated as being the initiators of major departures from a layer-by-layer growth mode whenever most of the deposited Fe atoms have sufficient mobility to reach these steps. However, even when the Fe atoms cannot reach these steps it appears that atomic place-exchange occurs with ≥25% of the top-layer Ag atoms. Atomic place-exchange mechanisms, which could account for this intermixing, have been observed in recent molecular-dynamics simulations of epitakial growth. Thus it seems probable that under the conditions that appear to produce layer-by-layer growth, the growth begins as layer-by-layer growth of an FeAg alloy, and only becomes layer-by-layer in pure Fe as the segregating Ag atoms gradually get left behind in the growing Fe film.
Grain Structure Interaction Between Cold and Hot Sputtered Aluminum Films
Authors: O'Meara David L.
Published: March 2011

The factors affecting the second layer grain structure of a two-aluminum-layer sputtered film were investigated with the use of a computer-aided experimental design and analysis program. A cold aluminum layer followed by a hotter aluminum layer has been described in the literature as a means of improving metal step coverage. Several factors were screened to determine the most important parameters by which the first layer influences the second. The two-layer interactions were determined by using scanning electron microscope (SEM) analysis to measure final grain structures. A model was generated from the experimental results that shows the influence of the first layer grain size on the second layer if the second sputter deposition is made above ∼300°C. The influence increases at higher temperatures. The results will be compared to grain growth models found in the literature.
The Effect of Deposition and Annealing Conditions on the Microstructure of Al-Cu and Al-Cu-Si Thin Films
Authors: Park M. , Krause S. J. , Wilson S. R.
Published: March 2011

The effect of deposition temperature and the addition of Si to sputter deposited Al-Cu thin-film microstructure was studied with transmission electron microscopy. Films were studied in the as-deposited and annealed condition. The effects of thermal treatment were studied with in-situ hot stage microscopy. Al2Cu (θ) precipitated at the grain boundaries and the sublayer interface. At higher deposition temperatures, with alloy composition in single phase region (Al-1.5 wt.%Cu), Al2Cu precipitated during cooldown. At lower temperatures, in the two phase Al-0 region, Al2Cu precipitated during deposition. The addition of Si caused formation of Si precipitates and retarded Al2Cu precipitation during deposition or cooldown.
On the Structure of Transformation Interfaces
Authors: Khalid F. A. , Edmonds D. V.
Published: March 2011

The transformation interfaces of some well known products of austenite decomposition in steels, namely pearlite, and proeutectoid grain boundary allotriomorphic cementite and Widmanstatten cementite, have been examined by TEM. This has been accomplished by using high- Mn high- C alloys that decompose at intermediate ageing temperatures but in which the untransformed parent austenite phase remains stable at room temperature, thus preserving the transformation interface. In conventional steels the residual austenite would undergo the martensite reaction, destroying the interface in the process. Defects in the interface have been analysed and related to intersections with stacking faults in the parent austenite phase. The nature and occurrence of these stacking faults, and their effect on the transformation, is considered.
Role of Interfaces in Coarsening and Grain Growth
Authors: Marsh S. P. , Glicksman M. E.
Published: March 2011

Theories of late-stage phase separation are discussed from the perspective of statistical mean-field approaches, whereby the material interfaces are assumed to interact with the appropriate average microstructural environment. For coarsening of two- and three-dimensional phases, recent progress is presented for selecting the most appropriate averages that characterize the microstructural environment surrounding a domain. The effective mean field, as well as the average interaction distance over which transport occurs, may be determined self-consistently by imposing global constraints that reflect the microstructural phase fractions and by using explicit spatial and ensemble averages of the matrix transport fields. Comparison of new theoretical coarsening rates with liquid-phase sintering experiments show good agreement over a wide range of phase fractions. Extension of this approach to grain growth, which involves more complex topological interactions, is also discussed.
Implications of Interface Structure on the Elastic Properties of Metallic Multilayers-The Case of the Supermodulus Effect
Authors: Jankowski Alan F.
Published: March 2011

The existence of the supermodulus effect, an enhancement in the elastic modulus of artificially layered metal films, was discovered more than a dozen years ago. Yet the detailed nature of this effect remains a puzzling phenomena. Implications of the interface structure on the elastic properties of gold-nickel multilayers are investigated using x-ray diffraction and high resolution electron microscopy.
Atomic-Level and Effective Elastic Moduli at Grain Boundaries
Authors: Alber I. , Bassani J. L. , Khantha M. , Vitek V. , Wang G. J.
Published: March 2011

The relationship between atomic structure and elastic properties of grain boundaries is investigated from both discrete and continuum points of view. A heterogeneous continuum model of the boundary is introduced where distinct phases are associated with individual atoms and possess their atomic level elastic moduli determined from the atomistic model. The complete fourth-order tensors of both the atomic-level and the effective elastic moduli are determined, where the latter are defined for sub-blocks from an infinite bicrystal and are calculated here for a relatively small number of atom layers above and below the grain boundary. These effective moduli are determined exactly for the discrete atomistic model, while only estimates from upper and lower bounds can be determined for the continuum model. Comparison between the atomistic results and those for the continuum model establishes the validity of this definition of elastic properties for heterogeneous structures at these scales. Furthermore, these comparisons as well as algebraic properties of the fourth-order tensor of moduli lead to criteria to assess the stability of a given grain boundary structure.