bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlation of Dislocation Loop Formation and Time Dependent Diffusion of Implanted P-type Dopants in Gallium Arsenide
Authors: Robinson H. G. , Deal M. D. , Stevenson D. A. , Jones K. S.
Published: March 2011

Recent experimental results indicate that diffusion of implanted p-type dopants in GaAs is time dependent under certain conditions. For Mg implanted at a dose of 1 × 1014 cm−2, the diffusion is constant for approximately an hour, then decreases by an order of magnitude or more. Be implanted at 1 × 1013 and 1 ×1014 cm−2 exhibits similar behavior, but with a shorter time before the diffusivity decreases. The diffusivity in 1 × 1013 Mg cm−2 implants, in contrast, remains constant for up to 16 hours. TEM micrographs of Be and Mg implants reveal dislocation loops in the higher dose samples, but not in the lower dose ones. During annealing, the loops grow and decrease in density, eventually disappearing completely from the crystal. This annealing of the loops appears to correlate to the time dependence of the diffusion. This behavior can be explained in terms of the substitutional-interstitial diffusion (SID) mechanism and point defect equilibria.
Ion Implantation Doping of InGaP, InGaAs, and InAlAs
Authors: Pearton S. J. , Kuo J. M. , Hobson W. S. , Hailemarian E. , Ren F. , Katz A. , Perley A. P.
Published: March 2011

The activation of Si+ and Be+ ions implanted into InGaP, InGaAs or InAlAs grown by GSMBE and OMVPE was investigated as a function of ion dose and annealing temperature. Activation efficiencies close to 100% were obtained in InGaP and InGaAs for Be doses up to ∼1014 cm−2 and annealing temperatures of 700–850°C. Activation of Be was less efficient in InAlAs. By contrast, implanted Si displayed a saturation in active sheet electron densities at 1–3 × 1013 cm−2 and required higher annealing temperatures for optimum activation efficiency. High sheet resistance (≤108 μ/□) regions were created by O+ implantation into n+ InGaP or InAlAs, with hopping conduction dominating carrier transport in the bombarded material. For post-implant annealing temperatures above 750°C, the conductivity was restored to its initial value. No evidence was found for the creation of electrically active oxygen-related deep levels in either material.
High-Energy Elevated Temperature Si and Room Temperature B Implants in InP
Authors: Nadella R. K. , Vellanki J. , Rao M. V.
Published: March 2011

High-energy (3 MeV) Si implantations were performed in InP:Fe at an elevated temperature of 200 °C for fluences 8×1014, 2×1015, and 5×1015 cm“2. For the 8×1014 cm−2 fluence, an activation of 82 %, carrier mobility of 1200 cm2/V-s, a peak carrier concentration of 9×1018 cm−3, and lattice quality comparable to that of virgin crystal were obtained. No amorphization takes place for any of the fluences used. Boron compensation implantations were performed in InP:Sn (n sime 2×1018 cm3) at room temperature in the energy range 1 to 5 MeV and fluence range 1011 to 1015 cm−2. After heat treatment, maximum resistivity of the order of 106 Ω-cm was obtained in B implanted InP.
Amphoteric Behaviour of Ge in InP: A RBS/Channeling and Differential Hall/Resistivity Study
Authors: Kringhøj P.
Published: March 2011

The lattice location of ion implanted Ga, Ge, and Se in InP has been determined with a combined RBS/channeling-PIXE technique and correlated to the carrier concentration and mobility profiles obtained with differential Hall/resistivity measurements.
The Electrical and Optical Properties of GaAs with as Precipitates (GaAs:As)
Authors: Warren A. C. , Woodall J. M. , Burroughes J. H. , Kirchner P. D. , Heinrich H. K. , Arjavalingam G. , Katzenellenbogen N. , Grischkowsky D. , Melloch M. R. , Otsuka N. , Mahalingam K. , Pollak F. H. , Yin X.
Published: March 2011

Since its initial report by the IBM/Purdue University group in 1990, GaAs with As precipitates (GaAs:As) has been shown by this group to exhibit unusual and useful electrical and optical properties. In this paper we review our progress in understanding the fundamental properties of this material. We have shown that both the electrical and optical properties of GaAs:As arc explained by assuming that the GaAs is of good crystalline quality and that the As precipitates act as buried Schottky barriers. This model accounts for its semi-insulating stability against both n- and p-type doping, its high-speed photoconductive behavior, and its ability to detect 1.3 micron light when it forms the “I” layer of a PIN photodiode via the internal photoemission process. Using modulation spectroscopy we clarify the fundamental differences between GaAs:As and unannealed GaAs grown at 200 C. We also show that GaAs:As used as a 1.3 micron detector in the metal-semiconductor-metal device structure format, has a photoconductive bandwidth in excess of 50 GHz.
Study of Transport Through Low-Temperature GaAs Surface Insulator Layers
Authors: Ibbetson J. P. , Yin L.-W. , Hashemi M. , Gossard A. C. , Mishra U. K.
Published: March 2011

Since epilayers of GaAs grown at low substrate temperature (LTGaAs) and annealed at 600°C were first demonstrated to be an effective buffer layer for eliminating backgating effects, the material properties and electronic characteristics of bulk LTGaAs have been actively investigated. Less attention has been paid to thin layers of LTGaAs (∼2000Å), although these have been shown to improve gate-to-drain breakdown characteristics when incorporated as the surface insulator layer in GaAs MISFET's. In bulk LTGaAs that has been annealed for 10 minutes at 600°C, the formation of arsenic precipitates with a density of 1018 cm-3 has been observed. These are considered to be at least partially responsible for the high resistivity of LTGaAs2. While the exact mechanism of precipitate formation is currently unknown, it would seem reasonable to expect the availability of the growth surface to have a significant effect on any defect redistribution during the anneal. This surface effect would become increasingly apparent as the LTGaAs layer thickness was decreased. It is desirable for MISFET applications that the LTGaAs gate insulator layer be as thin as possible, whilst maintaining high breakdown, in order to maximize device transconductance. To achieve this, it is important to understand how the observed bulk features (such as ∼60Å size arsenic precipitates) are affected in thin LTGaAs layers
A Gate Breakdown Mechanism in Mesfets and HEMTs
Authors: Trew R. J. , Winslow T. A. , Mishra U. K.
Published: March 2011

A model for gate breakdown in MESFETs and HEMTs is proposed. The model is based upon a combination of thermally assisted tunneling and avalanche breakdown. When thermal effects are considered it is demonstrated that the model predicts increasing drain-source breakdown as the gate electrode is biased towards pinch-off, in agreement with experimental data. The model also predicts, for the first time, the gate current versus bias behavior observed in experimental data. The model is consistent with the various reports of breakdown and light emission phenomena reported in the literature.
Picosecond High-Voltage Pulses Generation Using Low-Temperature (LT) GaAs
Authors: Motet T. , Nees J. , Williamson S. , Mourou G.
Published: March 2011

We report on the generation of 825 V electrical pulses with 1.4 ps rise time and 4 ps Full-Width-at-Half-Maximum using pulse biased Low-Temperature-grown GaAs photoconductive switch triggered by submicrojoule, 150 fs laser pulses. Dependence of the temporal pulse shape on both the electric field and the optical energy is observed and discussed.
TEM and HREM Studies of As-Grown Low-Temperature Molecular Beam Epitaxial In0.52Al0.48As/InP Heterolayers
Authors: Claverie A. , Liliental-Weber Z. , Werner P. , Swider W. , Bhatiacharya P. K. , Gupta S. , Mourou G.
Published: March 2011

Transmission and High Resolution Electron Microscopy have been used to study the dramatic changes in crystalline quality which occur in As-rich In0.52Al0.48As/InP layers when the growth temperature is lowered. We have found that for temperatures as low as 200°C and for a flux ratio of 20, the layers can be of high quality. For the lowest growth temperature of 150°C, pyramidal defects as well as hexagonal As grains are found which are characteristic of the breakdown of the monocrystalline growth in these layers. A mechanism for the formation of these defects is proposed based on their crystallographic structure. The fast photo response previously observed in these layers must be related to the presence of these defects.
Effect of Growth Conditions on Optical Response of GaAs Grown at Low Substrate Temperature by MBE
Authors: Schaff W. J. , Offsey S. D. , Song X. J. , Eastman L. F. , Norris T. B. , Sha W. J. , Mourou G. A.
Published: March 2011

The effect of growth conditions on the properties of GaAs grown by molecular beam epitaxy at low substrate temperatures has been studied. It has been found that the response time to 100 fsec 830nm light pulses is a function of substrate temperature and arsenic flux. The reason for variation of optical response with growth conditions is related to the nature of the incorporation of excess arsenic. A recent model proposed by Warren and others is invoked to explain the change in optical response with growth conditions. Further substantiation of this model comes from experiments on the annealing of low substrate temperature GaAs which has been doped with silicon.
STM Study of Diamond(001) Surface
Authors: Tsuno Takashi , Imai Takahiro , Nishibayashi Yoshiki , Fujimori Naoji
Published: March 2011

Undoped and boron-doped diamond epitaxial films were deposited on diamond(001) substrate by micro-wave plasma assisted chemical vapor deposition and their surfaces were studied by scanning tunneling microscopy in air. An atomic order resolution was confirmed for the observation.

For the undoped epitaxial films, which showed 2×1 and 1×2 RHEED patterns, dimer type reconstruction was observed and it was considered that the growth occurs through the dimer row extension. In the case of B-doped films, the dimer reconstruction was also observed. However, 2×2 structure due to the absence of dimer was partially observed.

The effect of boron concentration and methane concentration during epitaxial growth on the surface morphology were also studied. The morphology observed by STM became flatter, as the concentration of B-doping and methane concentration, during growth, increased.
Electronic Structure of N-V Centers and Terahertz Spectroscopy of Diamond
Authors: Redman D. A. , Shu Q. , Brown S. W. , Lenef A. , Lrj Y. , Whitaker J. , Rand S. C. , Satoh S. , Tsuji K. , Yazu S.
Published: March 2011

We report an essentially complete characterization of energies and relaxation processes of the lowest seven electronic states of the N-V (nitrogen-vacancy) center in diamond using several different nonlinear laser spectroscopie techniques. We have also applied ultrafast optical techniques to measure dielectric properties of CVD and bulk diamond in the 0.3–1.6 THz range for the first time.
Characterization of ZnS Layers Grown by MOCVD for Thin Film Electroluminescence (TFEL) Devices
Authors: Yu J. E. , Jones K. S. , Fang J. , Holloway P. H. , Pathangey B. , Bretschneider E. , Anderson T. J.
Published: March 2011

We have characterized MOCVD grown ZnS layers for thin film electroluminescence (TFEL) devices. Films with thicknesses ranged from several Å to 2 μm were studied by x-ray diffractometry (XRD), cross-sectional transmission electron microscopy (XTEM), high-resolution transmission electron microscopy (HRTEM), and ultraviolet-visible photospectrometry (UVS). From HRTEM micrographs, it was observed that ZnS films consist of a mixture of hexagonal and cubic phases. Correlation of UV absorption spectra with XRD analysis resulted in a method for quantitative determination of the cubic packing fraction of polymorphic ZnS films. The initial ZnS layer (< 1000 Å) deposited on BaTa2O6 had more hexagonal than cubic phase because of denser crystal defects. However, the fraction of cubic phase increased with the film thickness. In addition to film microstructures, the mean grain size, growth rate, film uniformity, and surface roughness of MOCVD grown ZnS thin films as functions of film thicknesses and substrate temperatures were also calibrated by XTEM results.
OMVPE Growth of ZnSe Utilizing Zinc Amides as Source Compounds: Relevance to the Production of p-Type Material
Authors: Rees William S. , Green David M. , Anderson Timothy J. , Bretschneider Eric
Published: March 2011

Growth of ZnSe on GaAs from H2S9 and Zn[N(TMS)2]2 precursors has been demonstrated. When Et2Zn is used as the zinc precursor a higher quality deposit is obtained. Results of experiments employing Et2Zn as the main zinc source with Zn[N(TMS)2]2 introduced at a dopant level indicate nitrogen has been incorporated. Final thin films were characterized by PL, XRD, SIMS, and Raman.
High Resolution Photoluminescence of EDGE and Near-Edge CdTe
Authors: Carmo M. C. , Soares M. J.
Published: March 2011

Among II-VI semiconductors CdTe is the one that can be grown in better crystal quality. However most of the edge and near edge luminescence properties are still to be clarified. CdTe can be obtained in both n and p type and conductivity type conversion is obtained under heat treatment.

In this work we studied the behaviour of a batch of CdTe samples under annealing in different conditions. We observed the growth and destruction of the 1.47 eV band and separated the 1.47 eV and 1.43 eV bands. We also show that these bands are strongly related with the chemical stoi chiometry.
Theoretical Studies of Diamond Surface Chemistry and Diamond-Metal Interfaces
Authors: Pickett W. E. , Pederson M. R. , Jackson K. A. , Erwin S. C.
Published: March 2011

Advances in diamond film growth have prompted us to study the interfaces involved in this process: the interface with the substrate, and the growth interface with the ambient hydrocarbon vapor. Carbon chemistry lies at the heart of the properties of both interfaces, and much of the relevant chemistry is not well understood. We report here the energies involved in some idealized chemical processes that may be important in the growth process. Results (Schottky barriers, interface energies) for diamond/metal interfaces are also reported, and the especially unusual diamond/nickel results we have recently obtained are discussed in some detail.
EPR Investigation of Defects in Boron Nitride thin Films
Authors: Fanciulli M. , Moustakas T. D.
Published: March 2011

Defects in BN thin films, produced by reactive sputtering, were investigated by Electron Paramagnetic Resonance (EPR) measurements. The EPR signals of films produced with up to 10% N2in the argon discharge are consistent with films having a cubic structure, and becoming more ordered with nitrogen incorporation in the films. The concentration of spins is in the order of 1019spins/g and they are attributed to nitrogen vacancies with an electron trapped in. Carbon incorporation changes the EPR signal and increases the concentration of spins significantly. This result is consistent with the notion that carbon doping stabilizes the electron in a nitrogen vacancy.
Thermoelectric Properties of Boron and Boron Phosphide Film
Authors: Kumashiro Y. , Yokoyama T. , Nakahura J. , Hatsuda K. , Yoshida H. , Takahashi J.
Published: March 2011

This paper describes the thermoelectric properties of amorphous or polycrystalline boron and boron phosphide films prepared using chemical vapor deposition and molecular beam deposition. The temperature dependencies of electrical conductivity of a-B and distorted B13P2 films obey the Mott's rule of loga vs T-1/4, while those of polycrystalline BP films have linear relationship between loga vs T-1. The a-B and B13P2 films have high electric resistivity and show p-type conductors while BP film shows n-type conductor. The estimated thermoelectric figure of merit of boron phosphide film is compatible to that of sintered specimen, but there remains some problems for a-B to alter.
Modeling of the Formation of Boron Carbide Particles in an Aerosol Flow Reactor
Authors: Xiong Yun , Pratsinis Sotiris E. , Weimer W.
Published: March 2011

The formation of submicron crystals of boron carbide (B4C) by rapid carbothermal reduction of intimately mixed carbon-boron oxide precursor powders in an aerosol flow reactor at temperatures above the boiling point of boron oxide is investigated. The employed high heating rates (105 K/s) of the process force release of gaseous boron oxide and suboxides and rupture of the precursor particles resulting in formation of boron carbide molecular clusters that grow to macroscopic particles by coagulation. Consequently, the formation and growth of B4C particles is described by simultaneous interparticle collision and coalescence using a two-dimensional distribution model that traces the evolution of both size and shape characteristics of the particles through their volume and surface area. Here, in addition to the coagulation term, the governing population balance equation includes a coalescence contribution based on B4C sintering law. The predicted evolution of the two-dimensional particle size distribution leads to a direct characterization of morphology as well as the average size and polydispersity of the powders. Furthermore, model predictions of the volume and surface area of boron carbide particles can be directly compared with experimental data of B4C specific surface area and grain size.
Investigation of Pt Bottom Electrodes for "In-Situ" Deposited Pb(Zr,Ti)O3 (PZT) thin Films
Authors: Bruchhaus Rainer , Pitzer Dana , Eibl Oliver , Scheithauer Uwe , Hoesler Wolfgang
Published: March 2011

The deposition of the bottom electrode plays a key role in the fabrication of ferroelectric capacitors. Processing at elevated temperatures of up to 800°C can give rise to diffusion processes and thereof formation of harmful dielectric layers.

In this paper we used Rutherford backscattering spectrometry (RBS), Auger electron spectrometry (AES) and transmission electron microscopy (TEM) to study Pt/Ti/SiO2/Si substrates with various thicknesses of the Ti and Pt layers. During heating up to about 450°C in vacuum the initial layer sequence remains unchanged. However, drastic changes occur when the electrodes are exposed to Ar/O2 atmosphere during heat treatment. Oxidation induced diffusion of Ti into Pt and oxidation of Ti were observed. A Pt electrode with a 100 nm thick Ti adhesion layer proved to be suitable for the "in-situ" deposition of PZT films.
Photoluminescence Investigation of Pb(Zr,Ti)O3 Thin Films
Authors: Zurcher Peter , Jones Raymond P. , Sun Yongchen , Cone R.L.
Published: March 2011

Photoluminescence (PL) excited at 1.7K with a N2-Laser (3.679eV) was used to investigate defect related electron-hole recombination transitions in ferroelectric PZT thin films. The interaction of doping, heat treatment, and hydrogen with the defect related PL spectrum has been studied. Donor/acceptor related transitions between 3.0 and 3.5eV and deep trap transitions between 2.0 and 2.6eV have been found. Certain heat treatments produce high densities of deep trap transitions in Pb(Zr0.48Ti0.52)03 thin films but not in 6% La doped PZT; different treatments are neccessary to produce similar deep trap transitions in the doped films. Hydrogen anneals eliminate the strongest deep trap transition at 2.15eV in both undoped and La-doped PZT films; however the donor/acceptor transitions are affected differently. Correlation with electrical properties seems to indicate the expected result: smaller defect densities are associated with better electrical performance.
Optical Properties of PZT, PLZT, and PNZT Thin Films
Authors: Peng Chien H. , Chang Jhing-Fang , Desu Seshu B.
Published: March 2011

Optical properties were investigated for undoped, La-doped, and Nd-doped Pb(ZrxTi1-x)O3 thin films deposited on sapphire substrates by metalorganic decomposition (MOD) process. Refractive index and extinction coefficient of these films were calculated from transmission spectra in the wavelength range of 300 to 2000 nm. The packing densities of these films were calculated from the refractive index data by using the effective medium approximation. Band gap energies of these films were also reported under the assumption of direct band-to-band transition. The refractive index and band gap energy of PZT films showed a linear dependence on Zr/Ti ratio. The refractive index decreased, while the band gap energy increased with increasing zirconium content. It was also found that both La-doped and Nd-doped PZT films had higher refractive indices than those of undoped PZT films with the same Zr/Ti ratio (50/50).
Ferroelectric Thin Films of Bismuth Titanate Prepared by Mocvd
Authors: Wang H. , Fu L. W. , Shang S. X. , Yu S. Q. , Wang X. L. , Lu Z. K. , Jiang M.H.
Published: March 2011

The ferroelectric thin films of bismuth titanate (Bi4Ti3O12) have been prepared by metalorganic chemical vapor deposition ( MOCVD) technique at atmosphere. The triphenyl bismuth (Bi(CaH5 ) 3)and tetrabutyl titanate (C16H36O4Ti) were used as precursors. Dense Bi4Ti3 O12 films with smooth shinning surface have been grown on Si( 100) substrates at 550°C whithout postannealing. The as- grown films were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy dispersion analysis ( EDAX). The films showed well-ordered crystallinity with an (001)preffered orientation. The influence of growth parameters on deposition rate, composition and morphology of as-grown films was also discussed.
BaTiO3 Thin Films Prepared by Organometallic Chemical Vapor Deposition
Authors: Wills L.A. , Wessels B.W. , Schulz D.L. , Marks T.J.
Published: March 2011

BaTiO3 thin films have been prepared by low pressure organometallic chemical vapor deposition on (100) MgO and (100) LaAlO3 substrates using the volatile precursors, titanium(IV) tetraisopropoxide and barium (hexafluoroacetylacetonate)2 (tetraglyme). The phase composition and structure of the films depends on the reactant partial pressure, growth temperature, and substrate. High quality, epitaxial BaTiO3 films can be prepared in-situ on LaAlO3 as confirmed by x-ray diffraction measurements. These BaTiO3 films exhibit smooth surface morphologies as evidenced by scanning electron microscopy. Electrical resistivity measurements indicate that the films are semi-insulating.
Chemical Vapor Deposition of Lead-Titanate
Authors: Greenwald Anton C. , Daly James T. , Kalkhoran Nader M.
Published: March 2011

Thin films of lead-titanate were deposited by chemical vapor deposition (CVD) using tetraethyl lead and titanium isopropoxide. Good high frequency hysteresis curves were obtained with platinum contacts. Low resistance of the material (estimated at 108 ohm-cm) affected low frequency measurements.

Optimized experimental parameters (pressure, temperature, gas flows, oxidizer) were derived from a designed experimental matrix using response surface methodology. This approach significantly reduced the number of deposition trials required.
Properties of Pzt Thin Films with 2CdO·B2O3Glass Phase Additive
Authors: Brooks Keith G. , Chen Jiayu , Udayakumar K. R. , Cross L. Eric
Published: March 2011

Lead zirconate titanate thin films containing 0-4 wt.% of 2CdO·B2O3glass phase additive have been fabricated by sol-gel processing. Smooth dense perovskite films of approximately 3500Å thickness were formed on Si wafers by a multiple layer spin coating process followed by rapid thermal annealing. Remanent polarizations of up to 23μC/cm2were measured. Hysteresis properties were found to be very sensitive to annealing time at 700°C, with remanence being maximized at 100-200 seconds.
Sol-Gel Derived Barium Sodium Niobate and Bismuth Titanate Films
Authors: Boulton J.M. , Teowee G. , Bomnersbach W.M. , Uhlmann D.R.
Published: March 2011

Sol-gel derived barium sodium niobate and bismuth titanate films were successfully prepared from precursor solutions of chelated Ba[Nb(OEt)6]2 and NaNb(OEt)6 and from bismuth 2-ethyl hexanoate and Ti(OEt)4 respectively. Single phase Ba2NaNb5O15 was formed at 750C on platinized Si and at 850C on fused SiO2. Monoclinic (pseudo-orthorhombic) Bi4Ti3O12 was formed at temperatures as low as 500C. Both film compositions showed significant second harmonic generation. The dielectric constant of the bismuth titanate film was comparable to that of sputtered films.
Fatigue Parameters of Lead Zirconate Titanate Thin Films
Authors: Yoo In K. , Desu Seshu B.
Published: March 2011

Temperature and voltage dependence of fatigue parameters were studied for PZT thin film capacitors on the basis of our fatigue model. It was found that the coefficient of dielectric viscosity of PZT and initial internal field difference of PZT capacitors play a key role in determining fatigue rate. Jump distance was calculated from voltage dependence of decay constant, and it turned out to be essentially the same as the lattice parameter. This result indicates that vacancies (oxygen vacancies, mainly) move parallel to the polarization direction during fatigue. Activation energy was calculated from the temperature dependence of the decay constant. It was confirmed that activation energy for domain wall movement determines fatigue rate at various temperatures. This fatigue model can be used to predict the fatigue behavior and can be extended to develop an accelerated test for fatigue.
Volatility and Thermal Stability of Lead bis-Heptafluorodimethyloctadione [Pb(fod)2] and Lead bis-Tetramethylheptadione [Pb(thd)2]
Authors: Nyman May , Desu Seshu B.
Published: March 2011

Lead bis-heptafluorodimethyloctadione, or Pb(fod)2 and lead bis-tetramethylbeptadione, or Pb(thd)2 are useful precursors for MOCVD of PbO, a component of PZT ferroelectrics. The two compounds differ only by substituents on their respective ligands, and properties such as volatility and thermal stability differ as a function of the substituents. The volatilities and thermal stabilities of Pb(fod)2 and Pb(thd)2 were examined and compared, in order to further determine usefulness as precursors for MOCVD. Pb(fod)2 and Pb(thd)2 were synthesized and purified via a procedure developed in our laboratory, and purity was confirmed by several techniques. Isothermal and dynamic thermogravimetric analysis experiments were carried out. Regions of thermal stability and thermal instability were identified as a function of heating time and temperature. The region of instability was further examined by heating experiments and chemical ionization mass spectrometry. It was proposed that vaporization of the monomeric form of Pb(fod)2 and Pb(thd)2 controls the rate of weight loss observed in the region of thermal stability, and oligomerization controls the observed rate of weight loss in the region of thermal instability. Heat of vaporization was calculated to be 75 KJ/mol for Pb(fod)2 and 86 KJ/mol for Pb(thd)2.
Observation of Structural Defects in Epitaxial Ferroelectric Bismuth Titanate/PrBa2Cu3O7 Superconductor thin Film Heterostructures on LaAlO3
Authors: Ghonge Subodh , Goo Edward , Ramesh R.
Published: March 2011

Epitaxial PrBa2Cu3O7 superconductor/ferroelectric bismuth titanate heterostructures grown on [001] oriented LaAlO3 by pulsed laser deposition are being studied. X-ray diffraction studies of the heterostructures have shown that all the layers grow in the c-axis orientation. In this investigation, the early stages of ferroelectric film growth have been studied using transmission electron microscopy (TEM) of crosssectioned samples. High resolution lattice imaging has been carried out to study the atomic structure of the ferroelectric/superconductor growth interface and the defect structure of the ferroelectric film.
Production of Molecular Clusters of Lithium Niobate by Ultraviolet and Visible Laser Ablation
Authors: Haglund R. F. , Tang K. , Chen C. H.
Published: March 2011

We have investigated laser ablation of molecular ions from the ferroelectric LiNbO3 at 532, 355 and 266 nm, comparing the effects of changing wavelength and intensity. The time-of-flight spectra show great sensitivity to the onset of plasma formation. Just below the plasma formation threshold, production of the monomer, dimer and trimer negative molecular ions were observed. Possible implications for thin-film deposition processing are discussed.
Compositional and Structural Properties of Sputtered Plzt Thin Films
Authors: Borrelli P.J. , Ballentine P.H. , Kadin A.M.
Published: March 2011

Thin films of lanthanum-modified lead zirconate-titanate (PLZT) were prepared by rf magnetron sputtering from a single oxide target onto a heated substrate. The target consisted of Pbl-xLaxZryTi1-yO3 with composition close to x=8% and y= 65%, either as a loose powder or a solid sintered disk. Under appropriate conditions, the desired perovskite phase formed in situ without any subsequent post-anneal. Film composition and structure were correlated with deposition parameters, including substrate temperature, target composition, gas pressures, and target aging. For deposition onto MgO or A12O3 crystalline substrates, perovskite PLZT films formed if there was sufficient Pb at the target surface, sufficient oxygen in the sputter gas (≈ 50%), and a substrate temperature >≈600°C. Target heating led to excessive Pb loss from the loose powder target; this was much less significant for the solid target. In addition, it was found that deposition onto an epitaxial perovskite substrate promoted formation of the perovskite phase, leading to an epitaxial film. A prototype ferroelectric capacitor was fabricated by depositing a conducting perovskite film (the high-Tc superconductor YBa2 Cu3O7 ) on a perovskite substrate, sputtering PLZT on top, with Ag for a top electrode. Measurements indicate a remanent polarization of 5 μC/cm2 and a coercive field of 900 V/cm.
Sol-Gel Pzt Films for Optical Waveguides
Authors: Swartz S.L. , Ramamurthi S.D. , Busch J. R. , Wood V.E.
Published: March 2011

Sol-gel processing is a candidate ferroelectric thin-film deposition method for electronic and electro-optic applications. At Battelle, sol-gel PbTiO3 and Pb(Zr,Ti)O3 films have been prepared on sapphire and single-crystal SrTiO3 substrates. Films deposited and annealed on sapphire substrates are crystalline with the perovksite structure and minimal crystallographic orientation, whereas films deposited on isostructural and lattice-matched SrTiO3 substrates exhibit a high degree of orientation. Guided-mode refractive index measurements were made using a single-prism method and film indices were computed. Refractive index values measured for PbTiO3 films (n = 2.58) and PZT films (n = 2.50) were slightly lower than values expected on the basis of bulk measurements. In double-prism experiments, optical wavcguiding was achieved over distances up to 10 mm in oriented PZT films on [100] SrTiO3substrates. Optical loss of 19 dB/cm was measured on one of these film samples. Such films, given requisite improvement in optical quality, may be suitable for useful optical waveguide devices. An approach is presented for the integration of ferroelectric waveguides onto silicon and/or GaAs substrates.
Applications of PZT and Related Thin Films in Piezoelectric Microsensors
Authors: Polla D. L. , Ye C. , Schiller P. , Tamagawa T. , Robbins W. P. , Glumac D. , Hsueh C.-C.
Published: March 2011

Ferroelectric thin films have been deposited on polycrystalline silicon micromechanical structures to form both physical microsensors and microactuator devices. These devices which include acoustic pressure sensors, infrared detectors, micropositioners, and stepper motors are based on either the piezoelectric or pyroelectric properties of sol-gel Pb(ZrxTi1-x)O3 or PbTiO3 deposited on surface-machined microelectromechanical structures. Several materials, micromachining, process integration, and performance issues are introduced in the description of these devices.
Photoelectric Properties of Undoped and Fe-Doped LiNbO3 Films Made by Sol-Gel Method
Authors: Cheng Chih-Hsing , Xu Yuhuan , Mackenzie John D.
Published: March 2011

Transparent lithium niobate (LiNbO3) with thickness from 0.1 - 1.2 μm were made on silicon, fused silica, and sapphire substrates by the sol-gel processing. Alkoxide solutions were used as starting materials. X-ray diffraction has been used to confirm the crystallization of the films. Refractive index, dielectric and ferroelectric properties of LiNbO3 films were studied. Absorption spectra of films of LiNbO3 and LiNbO3 with doping of different amount of Fe (0.1 - 2.5mol%) were measured. Short-circuit photocurrent measurements revealed both transient and steady state components attributed to a pyroelectric effect and a bulk photovoltaic effect respectively. Epitaxial growth of LiNbO3 thin film on sapphire(012) substrate by sol-gel method was also obtained.
Pyroelectric Microsensors by Sol-Gel Derived PbTiO3 and La-PbTiO3 Thin Films
Authors: Ye Chian-Ping , Tamagawa Takashi , Lin Ya-Yun , Polla D. L.
Published: March 2011

Ferroelectric PbTiO3 and Lanthanum-modified PbTiO3 thin films have been deposited on different substrate surfaces by sol-gel processing. The ferroelectric, dielectric, and pyroelectric properties and their temperature dependences have been investigated. The sol-gel derived thin films were integrated onto a membrane structure fabricated by solid-state surface-micromachining technology. The performance of the resultant devices have been tested as an uncooled infrared detector. The high voltage responsivity and short rise time are attributed to the combination of the pyroelectric film, the underlying polycrystalline silicon layer, and the thermal design of the composite structure. The addition of Lanthanum with a molecular fraction of 3% and 5% has resulted in a lower dielectric loss and a reduced thermal noise.
Compositional Dependence of the Quantum Efficiency of the Transition at 1.3 μm of Praseodymium in Halide Glasses
Authors: Swartz A. , Elyamani A. , Pafchek R. , Snitzer E. , Sigel G. H.
Published: March 2011

An improvement in the quantum efficiency of the 1.3 μm transition of Pr3+ has been acheived as a result of doping alternative halide glasses. An increase from 3.4% in ZBLAN [1] to 9.9% in a multicomponent halide glass is reported.
Enhancement of Optical Third Order Nonlinearity in Main-Chain Oriented Polythiophenes
Authors: Okawa Haruki , Wada Tatsuo , Sasabe Hiroyuki
Published: March 2011

The third order nonlinear responses for soluble one-dimensional ϕ-conjugated polymers, poly(3-alkylthiophene)s were investigated. Uniaxial stretching of the polymer film was carried out to align the polymer backbone. The stretched film showed large dichroism and crystallinity. Third order nonlinear susceptibility, χ(3)1111 of the stretched film was determined by optical third harmonic generation. A large enhancement of χ(3) due to the main chain alignment was observed.
Laser-Induced Fluorescence in Doped Metal Oxide Planar Waveguides Deposited from Aqueous Solutions
Authors: Hess Nancy J. , Exarhos Gregory J. , Wood Susanne M.
Published: March 2011

An aqueous route to the deposition of complex metal oxide films is based upon the complexation of the corresponding metal nitrate salts by glycine, followed by spin-casting the concentrated solution onto silica substrates. The presence of glycine serves to frustrate precipitation and leads to the formation of a glassy matrix through which metal cations are homogeneously dispersed. Subsequent heating of coated substrates initiates an oxidation-reduction reaction which removes the organic matrix and residual nitrate leaving behind a film of the desired oxide composition. Using this method, ruby (Cr:Al2O3) and Sm:YAG (Sm:Y3Al5O12) films on the order of 150 nm thick have been deposited. The respective phases have been confirmed by XRD data and from the measured fluorescence spectra.

The red fluorescence exhibited by these materials under 488 nm excitation is dependent upon the ambient temperature and pressure. A marked shift in wavelength is observed as a function of increasing pressure. Ruby also exhibits a temperature dependent wavelength shift in contrast to Sm:YAG where a negligible shift is seen to temperatures near 1200 K. Fluorescence lifetimes of both materials exhibit a temperature dependence which varies with dopant concentration. This work suggests the possible application of these films as pressure-temperature sensors in a planar waveguide configuration or as a coating material for optical fibers. Details of the deposition process will be reviewed and the fluorescence response of both types of films will be summarized.
Formation of Planar and Strip Waveguides in KNbO3 by He Ion Implantation
Authors: Fluck D. , Fleuster M. , Irmscher R. , Günter P. , Buchal C H.
Published: March 2011

Single crystals of KNbO3 have an excellent potential for integrated and nonlinear optical applications. MeV He ion implantation is a reliable technique for the formation of permanent optical waveguides in this material. We have fabricated planar and strip waveguides using He energies between 1 and 3.5 MeV and ion doses of 5 × 1013 to 1016 ions/cm2. Waveguides were analyzed at a wavelength of 514, 633 and 860 nm.
Permanent Photoinduced Refractive Index Changes in Rare Earth Doped Glasses
Authors: Williams Glen M. , Ruller Jacqueline A. , Friebele E. Joseph
Published: March 2011

Permanent refractive index gratings were holographically photowritten into rare earth doped glasses using the 488 rn line of a Ar Ion laser. The rare earths Pr3+, Tb3+, and Eu2+ were examined. Experiments were performed to elucidate the mechanism responsible for the photoinduced index change. A model is presented in which the index change is accomplished through photoionization of the rare earth dopant and subsequent trapping of the free carrier. The viability of these materials for use in optical fiber grating devices is discussed.
Mechanical Properties of SiO2vs. SiO2-TiO2Bulk Glasses and Fibers
Authors: Gulati Suresh T.
Published: March 2011

The mechanical properties of silica and titania-doped silica glasses, in bulk and fiber forms, are presented. These include the elastic properties (E and ν), strength distribution (in tension and bending), fatigue behavior (dynamic and static loading) and fracture toughness. Following a brief review of above properties for fused silica and ULE™ glasses (Coming Codes 7940 and 7971), used primarily for space applications, the mechanical properties data for silica and titania-doped silica-clad optical fibers are presented. The enhancement of mechanical performance of titania-doped silica clad fiber is also discussed.

The effect of titania doping on fundamental properties like stress-free activation energy, crack tip pH, and deformation mode of Si-O-Si bond is discussed. In addition, the crack velocity data obtained from DCDC specimens of homogeneous silica and titania-doped silica glasses are compared in an attempt to understand the role titania plays in improving the fatigue resistance of optical fibers.
Radiation Response of Pure Silica Core Optical Fibers. IV
Authors: Skutnik Bolesh , Henschel H. , KÖhn O. , Schmidt H. U.
Published: March 2011

The radiation response of a series of optical fibers with pure silica cores, that differed as to residual hydroxide and chloride content and as to preform formation, have been measured after exposure to pulsed electron beam radiation to 10 krads [100 Gys]. The irradiations were carried out at both ambient temperature and at −50°C and with two different operating power levels at each temperature. The responses have been analyzed seeking to identify correlations between the differences in the residual chemical contents or preform formation and the observed differences in the initial response and the recovery behavior among the optical fibers in the series.
Influence of Residual Water on the Strength of Metal Coated Optical Fibers
Authors: Bubnov M. M. , Dianov E. M. , Semjonov S. L.
Published: March 2011

The influence of residual moisture under a metal coating on strength and fatigue of silica optical fibers was investigated. It was shown that for the fabrication of metalcoated fibers with strength – 10 GPa and low static fatigue it is necessary that the water content in the atmosphere during the freezing process should be less than 40 ppm.
Alkali Activated Cementitious Materials: An Overview
Authors: Roy D. M. , Silsbee M. R.
Published: March 2011

Alkali-activated cementitious materials have considerable potential, with properties ranging from very high early strength to very high long term strength and low porosity. The role of alkalis in activating industrial by-products such as ground granulated (glassy) blast-furnace slag, ultra-fine silica fume or other by-product silicas, glassy fly ashes, and other amorphous materials is discussed. These by-product materials are activated by alkali additions which break the strong silicon oxygen bonds in the silicate or alumino-silicate network, accompanied by the formation of new reaction products. The role of the different components in multi-component activated cements on the reactivity and the nature of the resultant products is discussed. Characterization of starting materials and reaction products by XRD, SEM (including environmental SEM), chemical, and particle characterization techniques has been made. Additional results include investigation of pore solution chemistry as a function of time. Some inferences for long term durability are discussed.
Preparation and Hydration Kinetics of Pure CaAl2O4
Authors: Gulgun M. A. , Popoola O. O. , Nettleship I. , Kriven W. M. , Young J. F.
Published: March 2011

Single phase, pure monocalcium aluminate (CaAl2O4) powders are chemically synthesized at temperatures as low as 900°C. The powders have a specific surface area of approximately 10 m2/g. The hydration kinetics of CaAl2O4 and the morphology of the hydrates are analyzed using electron microscopy techniques
Effect of Starting Materials on the Synthesis of Tobermorite
Authors: Sato Hiroyoshi , Grutzeck Michael
Published: March 2011

The effect of starting materials on the synthesis of tobermorite was studied using29Si MAS and CPMAS NMR Spectroscopy. Three Q2 and one Q3 peak were identified during the crystallization of tobermorite from C-S-H. C-S-H, which had a Ca/Si ratio >1, crystallized readily because this C-S-H consists of dimer and short chains of silica tetrahedra. This occurred whenever quartz was used as a starting material. C-S-H, which had a Ca/Si ratio <1 was harder to crystallize because this C-S-H consists of long and cross-linked chains of tetrahedra. The latter was observed when amorphous silica was used as a starting material.
Experimental and Computer Simulation Results for the Electrical Conductivity of Portland Cement Paste
Authors: Christensen B.J. , Mason T.O. , Jennings H.M. , Bentz D.P. , Garboczi E.J.
Published: March 2011

The electrical conductivity of portland cement paste is an important transport property, especially since, when properly normalized by the pore fluid conductivity, it is equivalent to the normalized ionic diffusivity of the material via the Nernst-Einstein relation. This paper presents experimental and computer simulation results for σ/σo, where σ is the conductivity of the bulk paste as determined from impedance spectroscopy, and σo is the conductivity of the pore solution. Comparison between simulation and experiment is carried out for an 0.5 water:cement ratio white cement paste as a function of capillary porosity. The quantitative agreement between theory and experiment is reasonable.
The Development of Microstructure in Calcium Sulphoaluminate Expansive Cement
Authors: Herrick John , Scrivener Karen L. , Pratt Peter L.
Published: March 2011

Using backscattered electron images, it is shown that an expansive clinker is polymineralic in nature, with individual particles containing the constituents (lime, anhydrite and anhydrous calcium sulphoaluminate) to form ettringite on hydration. The hydration reaction with time of a simple paste of a mixture of this expansive clinker with Ordinary Portland Cement (OPC) has been monitored using backscattered electron images, and the formation of ettringite and a change in the morphology of the calcium hydroxide formed from the added free lime from the expansive clinker is observed. Thermal analysis studies on pastes of the pure expansive clinker have confirmed this apparent change in morphology.
SO3-Rich Portland Cements: Synthesis and Strength Development
Authors: Abdul-Maula S. , Odler I.
Published: March 2011

Up to 8 per cent of SO3 may be incorporated into the crystalline lattice of C2S if burned in the presence of CaSO4. C3S may be formed only in the presence of F-. Under these conditions up to 5 per cent of SO3 may be incorporated. In the presence of CaSO4 and CaF2 in the raw meal portland clinkers may be formed that contain simultaneously the phases C3S and C4A3S. Clinkers of this kind yield cements with favorable strength properties at “optimum gypsum” additions.
The Nature of the Concrete-Steel Rebar Interface in Plain and Silica Fume Concrete
Authors: Zayed Abla M.
Published: March 2011

In this investigation the nature and morphology of the concrete-reinforcing steel interface is studied. The effect of the partial replacement of cement by silica fume on the interface microstructure was determined. The distribution profiles of percentage porosity, calcium hydroxide and unreacted cement from the interface towards the concrete bulk were measured using the scanning electron microscope operated in the back scattering mode. The findings indicate the similarities between the morphology of the concrete-steel interface and those reported earlier in the literature for the concrete-aggregate interface. Additions of silica fume resulted in a decrease of the interface porosity and calcium hydroxide content.
Statics of Phase Transformation in Ni-Al, Ni-Ti And Cu-Zn: a First Principles Study
Authors: Turchi P. E. A. , Sluiter M.
Published: March 2011

We show that the interplay between electronic structure properties, crystalline effects and local chemical order is quite distinct for Ni-Al, Ni-Ti and Cu-Zn, although they all exhibit a first order displacive transformation upon cooling from a high temperature partially ordered B2 phase. For this purpose, electronic structure and phase stability properties of these three alloys are investigated with a first principles approach. The study is based upon the Generalized Perturbation Method applied to the Korringa-Kohn-Rostoker multiple scattering description of the Coherent Potential Approximation, and temperature effects are taken into account within a generalized mean field approach.
Shape Memory Effect with Low MsThermoelastic thin Plate Martensite in an FE-33Ni-12CO-5Ti Alloy
Authors: Jian Li , Chou C. C. , Wayman C. M.
Published: March 2011

An Fe-33Ni-12Co-5Ti (wt.%) alloy was subjected to aging treatments to determine the effect of ausaging (at 700 °C for 5, 10 and 30 hr) on the martensitic transformation and shape memory effect. The Mstemperatures were determined by electrical resistance measurements and microstructures were examined by TEM. The shape memory was studied by bending specimens in liquid nitrogen and found to be associated with a low Msthermoelastic thin plate martensite.
Surface Energy and Microstructure
Authors: Kohn Robert V. , MÜtller Stefan
Published: March 2011

Bulk energy considerations can predict the gross features of microstructures observed in martensitic phase transitions, but not finer details such as the length scale on which twinning occurs. These are determined by surface energy. A standard approach is to minimize the sum of bulk and surface energy within the class of “twinned” configurations. This leads to the conclusion that the twin width w and the twin length L should satisfy w ∼L∼. While that seems to be the rule, a different structure is sometimes observed, for example in In-Tl and Cu-Al-Ni. It involves successive coarsening of the twins away from an austenite/twinned-martensite interface.

We re-examine the minimization of bulk plus surface energy. Our analysis differs from prior ones in that it permits configurations which are not essentially “onedimensional” to compete in the minimization. We find that the global minimum of energy can be either “one-dimensional” or “branched,” depending on the relative values of the elastic moduli and surface energy density.