bluuebunny/crossref_metadata_2025 huggingface dataset:
Ionotropically Gelled Bicontinuous Cubic Phase as a Matrix for Controlled Release
Authors: Puvvada S. , Naciri J. , Ratna B. R.
Published: March 2011

Release studies from a lipid-based matrix, known as the bicontinuous cubic phase, are presented. This matrix consists of nano-sized pores within which various proteins and drugs can be dispersed and subsequently released to the exterior. To control the release rate, the aqueous pores of the cubic phase were gelled using sodium alginate, a water soluble polysaccharide. Studies show that the release rate is significantly lowered upon gelation and the first order release profile exhibited by the ungelled cubic phase is converted to a zeroorder linear profile. Further, it has been shown that the release trends can be reversed by degelation. This opens up the possibility of releasing large quantities of the protein when required (drugs on demand concept) by degelling the gelled samples.
Preliminary XPS Spectroscopic Characterization of Autoclaved TiNi Shape Memory Alloys for Implants
Authors: Shabalovskaya Svetlana A. , Anderegg J. W. , Sachdeva R. L. C. , Harmon B. N.
Published: March 2011

This paper reports a preliminary spectroscopic characterization of the surface elemental and phase compositions of Ti49Ni51 alloy treated using various sterilization procedures (autoclaving in water, steam, sealed envelopes; boiling in water and chemical etching). The surface of TiNi is found to consist of a thin oxide covered by a carbon-dominated contamination layer. The surface oxide of autoclaved samples is (TiO2)xNiy where y varies in the range 0-6 at.% depending on the surface preparation procedure. Minor amounts of suboxides as well as metallic Ni are also detected. Preliminary estimations of the oxide film thickness showed that it varies in the range 7- 26 nm depending on the employed method of sterilization. Mechanisms of surface state formation are briefly discussed.
Synthesis and Characterization of Tetraethylene Glycolpoly(Ethylene Oxide) Hydrogels for Tissue Engineering Applications
Authors: Royappa A. T. , Lopina S. T. , Cima L. G.
Published: March 2011

A new poly(ethylene oxide) based biomaterial has been synthesized by co-crosslinking linear poly(ethylene oxide) (PEO) with tetraethylene glycol (TEG) in aqueous solution using electron beam radiation. This process results in hydrogels with variable concentrations of hydroxyl groups, tunable by adjusting the concentration of TEG in solution. FTIR analysis of these gels shows no changes in chemical composition on crosslinking.
High Porosity Polymeric Carbon Ware for Controlled Release of Drugs
Authors: Ila D. , Jenkins G. M. , Zimmerman R. L. , Evelyn A. L.
Published: March 2011

Polymeric carbon ware prepared at various temperatures with variable accessible pore volume was filled with lithium by submerging in molten LiCl at 700°C. Using Li(p,α) nuclear reaction analysis the concentration profile and the volume density of Li were measured. It was found that they were highest for polymeric carbon samples prepared at 650°C.
A Novel Biodegradable Poly(Lactic-Co-Glycolic Acid) Foam for Bone Regeneration
Authors: Thomson Robert C. , Yaszemski Michael J. , Powers John M. , Mikos Antonios G.
Published: March 2011

We present a novel method for manufacturing three-dimensional, biodegradable poly(DL-lactic-co-glycolic acid) (PLGA) foam scaffolds for use in bone regeneration. The technique involves the formation of a composite material consisting of gelatin microspheres surrounded by a PLGA matrix. The gelatin microspheres are leached out leaving an open-cell foam with a pore size and morphology defined by the gelatin microspheres. The foam porosity can be controlled by altering the volume fraction of gelatin used to make the composite material. PLGA 50:50 was used as a model degradable polymer to establish the effect of porosity, pore size, and degradation on foam mechanical properties. The compressive strengths and moduli of PLGA 50:50 foams were found to decrease with increasing porosity but were largely unaffected by pore size. Foams with compressive strengths up to 2.5 MPa were manufactured. From in vitro degradation studies we established that for PLGA 50:50 foams the mechanical properties declined in parallel with the decrease in molecular weight. Below a weight average molecular weight of 10,000 the foam had very little mechanical strength (0.02 MPa). These results indicate that PLGA 50:50 would not be suitable as a scaffold material for bone regeneration. However, the dependence of mechanical properties on porosity, pore size, and degree of degradation which we have determined will aid us in designing a PLGA foam (with a comonomer ratio other than 50:50) suitable for bone regeneration.
Biodegradable Foams for Cell Transplantation
Authors: Lo H. , Kadiyala S. , Guggino S. E. , Leong K. W.
Published: March 2011

A processing technique based on the principle of phase separation was developed to fabricate three-dimensional microcellular foams to act as templates for cell transplantation. The polymers used to make the foams were polylactic acid (PLLA) and a polyphosphoester (BPA/PP). The resulting foams had relatively uniform, open cells throughout the matrix. The foams could also be fabricated into complex shapes to meet specific design requirements. The foam morphology and microstructure were characterized by mercury porosimetry and scanning electron microscopy. Osteoblast like cells ROS17/2.8 were successfully cultured in the foams. Cell attachment to the foam interior was verified by confocal microscopy. The fabrication technique allows incorporation of drugs or nutrients into the highly porous structure as demonstrated by the intimate dispersion of fluorescein isothiocyanate (FITC) in the matrix.
Attachment of Mucin Specific Lectins to Alginate for Use as Bioadhesives
Authors: Chickering Donald E. , Jacob Jules S. , Keung Annie , Desai Tejal A. , Mathiowitz Edith
Published: March 2011

The use of bioadhesive materials for orally-delivered, controlled release systems could increase GI transit time and improve bioavailability. Through the covalent attachment of various ligands to drug delivery systems it is possible to engineer materials to adhere to specific moieties endogenous to the alimentary mucosal layer. The entire GI tract is covered by a continuous, protective, mucous coating made of 95% water and 5% electrolytes, lipids, proteins, and glycoproteins. The GI glycoproteins consist of a protein core with covalently attached carbohydrate side chains terminating in either L-fucose or sialic acid residues. There exist several plant and animal lectins which display high affinity binding to either of these sugars.

We have studied the effect on bioadhesion of attaching biotinylated Ulex Europaeus I (UEA-I), an L-fucose specific lectin derived from the gorse seed, to barium-loaded alginate microspheres. Two carbodiimidazole (CDI) coupling procedures were investigated: premicrosphere-fabrication coupling and post-microsphere-fabrication coupling. The attachment of lectin was confirmed using an ABC reaction with HRP staining. The pre-modified microspheres clearly showed better labeling than the post-modified. For in vivo assessment of bioadhesion, 3 cohorts of 4 rats were force fed slurries of control, pre- and post-modified microspheres in saline. The animals were X-rayed 1 hour after feeding and sacrificed 19 hours later. Their entire GI tracts were excised, X-rayed and the microsphere distribution was assessed. The premodified microspheres showed greater retention in all areas of the alimentary canal. The total percentage of microspheres remaining in the GI tract after 19 hours was: 18.6% post-modified and 37.1% pre-modified. These results correlate well with the intensity of the reaction seen with the HRP staining, and suggest that attachment of mucin specific ligands to polymer microspheres may improve bioadhesion.
Gas Phase and Gas Surface Kinetics of Transient Silicoin Hydride Species
Authors: Jasinski Joseph M.
Published: March 2011

This paper presents a summary of the current state of our understanding of the absolute reactivity of transient silicon hydride species, such as SiH, SiH2and SiH3in the gas phase and at the surface of thin films.
Reaction Kinetics on Diamond: Measurement of HI Atom Destruction Rates
Authors: Harris Stephen J. , Weiner Anita M.
Published: March 2011

We describe the first measurements of reaction kinetics between diamond and a gas phase species—H atoms—involved in its formation. We develop a remarkably simple method to measure H atom concentrations and use the method to measure γd, the destruction probability of H atoms on diamond at 20 torr and 1200 K. We find γd = 0.12. This value is close to that estimated from gas phase alkane rate constants.
A Novel Molecular Beam Reactor for The Study of Diamond Surface Chemistry
Authors: Wolden C. A. , Zau G. , Conner W. T. , Sawin H. H. , Gleason K. K.
Published: March 2011

A novel reactor has been constructed to investigate the fundamental surface kinetics of diamond chemical vapor deposition(CVD). The molecular beam reactor permits independent control of the atomic hydrogen flux, the methyl radical flux and the substrate temperature. The low pressure in the growth chamber (≈ 1 mTorr) minimizes the impact of gas-phase chemistry. The reactive mixture impinging the substrate is sampled through an orifice and analyzed by mass spectroscopy. Differential pumping in the two adjacent chambers quenches the beam, allowing quantitative analysis of radical species such as H and CH3. In preliminary experiments deposition was achieved onto seeded molybdenum substrates.
The Role of Unprecracked Hydride Species Adsorbed on The GaAs(100) in The Growth of GaAs by Ultrahigh Vacuum Chemical Vapor Deposition Using Trimethylgallium and Triethylgallium
Authors: Park Seong-Ju , Ro Jeong-Rae , Sim Jae-Ki , Ha Jeong Sook , Lee El-Hang
Published: March 2011

Abstracts

We have grown GaAs epilayers by ultrahigh vacuum chemical vapor deposition(UHVCVD) using adsorbed hydrides and metalorganic compounds via a surface decomposition process. This result indicates that unprecracked arsine(AsH3) can be used in chemical beam epitaxy(CBE) and that a new hydride source with a low decomposition temperature, monoethylarsine(MEAs) can replace the precracked AsH3 source in CBE. The impurity concentrations in GaAs grown with trimethylgallium(TMG) and triethylgallium(TEG) were found to be very sensitve to growth temperature. It was also found that the uptake of carbon impurity is significantly reduced when TMG is replaced with TEG. The carbon concentrations in epilayers grown using TMG and TEG with unprecracked AsH3 and MEAs were reduced by 2-3 orders of magnitude compared to those by CBE process employing TMG and arsenics from precracked hydrides. We have also found that the hydrogen atoms play an important role in the reduction of carbon content in GaAs epilayer. Intermediates like dihydrides from MEAs decomposed on the surface are considered to supply hydrogen atoms and hydrides during growth, which may remove other carbon containing species.
Controlled Impurity Introduction In CVD: Chemical, Electrical, and Morphological Influences
Authors: Kuech T. F. , Redwing J. M. , Huang J.-W. , Nayak S.
Published: March 2011

We present here an overview of recent studies of the influence of oxygen doping on the electrical and structural properties of semiconductors grown through the metal organic vapor phase epitaxy (MOVPE) technique. In particular, we have measured the impact of oxygen introduction on several of the principal aspects of the growth process: incorporation, activation, and influence on the growing surface structure. The gas phase chemistry and dopant incorporation was investigated for two different precursors: dimethyl aluminum methoxide and diethyl aluminum ethoxide. The simple change in the structure of the oxygen source leads to significant changes in the oxygen incorporation behavior. Complementary studies of the gas phase decomposition of these oxygen sources have indicated that the decomposition mechanism is substantially different for these two sources leading to the change in incorporation behavior. The impact of the selective incorporation of oxygen at heterointerfaces has been studied here through the growth of superlattice structures. Glancing angle X-ray diffraction and atomic force microscopy measurements have shown that the incorporation of oxygen at the GaAs-to-AlxGaI-x As interface leads to modest increases in the average roughness of the heterointerface with more significant changes in the interfacial structure. The structure of this interfacial roughness was also studied through measurements of the diffuse X-ray scattering about a Bragg peak. Measurements of the component of the roughness which is correlated between the superlattice layers show significant changes with oxygen addition.
Probing Selective Deposition of Aluminum Using in Situ Infrared Spectroscopy
Authors: Gladfelter Wayne L. , Simmonds Michael G. , Zazzera Larry A. , Evans John F.
Published: March 2011

Dimethylethylamine alane (DMEAA) has been used to deposit thin films of aluminum selectively on gold in the presence of silicon oxide. This paper presents studies of the effect of temperature, pressure, and substrate pattern on the selectivity. A specially designed reactor allowed us to probe the structure of the species on the silica surface using infraed spectroscopy. At room temperature two absorptions in the Al-H stretching region were assigned to two species; weakly bound molecules of the intact precursor and a strongly bound dihydride formed from the reaction of DMEAA with surface bound (and H-bonded) hydroxyls (from H2O or silanol groups). At higher temperatures the CH vibrations of the amine disappeared, and the Al-H stretch shifted to higher energy. A weak absorption at 2250 cm−1 attributable to a Si-H also appeared. The impact of these observations on the loss of selectivity is discussed.
Influence of Flow Dynamics on The Morphology of CVD Aluminum Thin Films
Authors: Speckman Donna M. , Leung Denise L. , Wendt Jerry P.
Published: March 2011

Aluminum thin films were deposited by chemical vapor deposition on SiO2 substrates using trimethylamine alane (TMAA) in a low pressure CVD reactor system. A high TMAA flow rate during deposition, combined with an initial burst of added argon during the nucleation of the substrate surface resulted in the growth of aluminum thin films with excellent purity and surface morphologies. Film resistivities averaged 3.4 μΩ-cm, and the average surface peak-to-valley height for each film was found to be <4% of the film thickness. The surfaces of films with thicknesses of ≤ 1 μm were extremely smooth and reflective. In contrast, the use of a high alane flow rate in the absence of any added argon resulted in the growth of films with extremely textured surface morphologies. Furthermore, films grown using an argon carrier gas, but with a slow alane flow rate, exhibited both textured surface morphologies and whisker growth.
Deposition of Tungsten Films by Pulsed Excimer Laser Ablation Technique
Authors: Dhote A.M. , Ogale S.B.
Published: March 2011

Low temperature deposition of W on Semiconductor substrates is vital for microelectronics technology. Laser ablation technique using KrF (248 nm) excimer laser has been employed to deposit W films from W(CO)6. The substrates used are Si(100) and SiO2. The influence of substrate temperature on the film growth rate was investigated in a broad temperature range (20 - 500 °C), keeping the laser fluence fixed at 0.4 Jcm−2. The substrate temperature is found to have a strong influence on the resistivity of the deposited films. Film resistivities within a factor of 3 of the value for pure bulk W have been observed in the substrate temperature range of 300 - 500 °C. X-ray diffraction data were also obtained. These revealed that the crystal structure of the film deposited in this temperature range corresponds specifically to the m-phase. Optical emissions from the plasma generated during the pulsed excimer laser ablation of W(CO)6 are also examined by an optical Multichannel Analyser (OMA).
Gaas Etching by C12 and HCI: Ga- vs. As- Limited Etching
Authors: Su Chaochin , Dai Zi-Guo , Hou Hui-Qi , Xi Ming , Vernon Matthew F. , Bent Brian E.
Published: March 2011

Results in the literature indicate that C12 etches GaAs at room temperature but HCl etches GaAs at a measurable rate only at temperatures above ∼670 K. In this work, molecular beam scattering and surface analysis techniques have been applied to address the fundamental kinetic differences between these two systems. The results indicate that the onset of GaAs etching by C12 is determined by the kinetics of Ga-removal as GaC13 while etching by HCl is limited by As evaporation as As2. The results also suggest that HCl selectively etches gallium from GaAs at temperatures between 600 and 650 K.
Chemical Topography of Si Etching in a Cl2 Plasma, Studied by X-RAY Photoelectron Spectroscopy and Laser-Induced Thermal Desorption
Authors: Donnelly V. M. , Guinn K. V. , Cheng C. C. , Herman I. P.
Published: March 2011

This paper describes x-ray photoelectron spectroscopy (XPS) studies of etching of Si in high-density Cl2 plasmas. Polycrystalline Si films, masked with photoresist stripes, are etched and then transferred in vacuum to the XPS analysis chamber. Shadowing of photoelectrons by adjacent stripes and differential charging of the photoresist and poly-Si were used to separate contributions from the top of the mask, the side of the mask, the etched poly-Si sidewall, and the bottom of the etched trench. In pure Cl2 plasmas, surfaces are covered with about one monolayer of Cl. If oxygen is introduced into the plasma, either by addition of O2 or by erosion of the glass discharge tube, then a thin Si-oxide layer forms on the sides of both the poly-Si and the photoresist. Laser-induced thermal desorption (LITD) was used to study etching in real time. LITD of SiCI was detected by laser-induced fluorescence. These studies show that the Si-chloride layer formed during plasma etching is stable after the plasma is extinguished, so the XPS measurements are representative of the surface during etching. LITD measurements as a function of pressure and discharge power show that the etching rate is limited by the positive ion flux to the surface, and not by the supply of Cl2, at pressures above 0.5 mTorr and for ion fluxes of σ4× 1016cm−2 s−1.
Confinement and Low-Energy Extraction of Photo-Fragment Ions Using Rf Ion Trapping
Authors: Yamamoto Seiji , Mochiji Kozo , Ochiai Isao , Mikami Naohiko
Published: March 2011

Spatial confinement of mass-selected ions and extracting them to a solid surface at low kinetic energy is achieved by using rf ion trapping which is combined with multi-photon ionization by a KrF laser. SF5+ fragment ions of SF6 generated by photo-ionization are separated from other ionic species and then confined in the cylindrical ion trap cell for at least 100 ms. The stored ions are extracted onto the seniconductor surface. This technique is promising for clarifying surface reactions of semiconductors, which is the key to controlling surface structure on an atomic scale.
The Impact of Gas Phase and Surface Chemical Reactions on Step Coverage in Lpcvd
Authors: Raupp Gregory B. , Cale Timothy S.
Published: March 2011

The characteristic step coverage behavior which a given LPCVD process exhibits depends on the nature of the controlling gas phase and/or surface chemical reactions. Physically-based ballistic transport and reaction film profile evolution simulation has provided a structure wherein the origins of step coverage limitations can be understood in the context of the interaction of transport and the controlling chemistry. Based on comparisons of the simulations to literature and in-house experimental data, we have categorized LPCVD mechanisms into one of three types. In heterogeneous deposition, conformal step coverage can usually be found under at least some process conditions. Step coverage typically degrades with increasing deposition temperature. In homogeneous precursor-mediateddeposition, a reactive intermediate is formed in the gas-phase above the wafer surface, resulting in poor to moderate step coverage. Step coverage may or may not degrade with increasing temperature. In byproduct-inhibited deposition, a gas-phase byproduct generated via a surface reaction readsorbs on the growing film surface and slows the deposition rate, yielding a poor to moderate, relatively temperature-insensitive step coverage. Poor step coverage is manifested in a marked film thickness discontinuity at the feature mouth, with a relatively uniform film down the feature sidewalls.
Surface Reaction Intermediates in Ge Chemical Vapor Deposition on Silicon
Authors: Greenlief C. Michael , Keeling Lori A.
Published: March 2011

Computational programs are often used for estimating molecular orbital energies and geometries. The results of these calculations can also provide information needed for investigation of adsorption and decomposition mechanisms on surfaces. In this study, ab initio methods are used to calculate properties of gas phase diethylgermane and GeHx-substituted silanes (x=1−3). The silanes are used as models for surface Ge hydrides. The calculated gas phase molecular orbital energies are then compared with experimentally determined molecular orbital energies for the adsorbed species. The surface species are prepared by germane, digermane, ethylbromide, or diethylgermane adsorption on the Si(100)-(2×1) surface and the molecular orbital energies are measured by photoelectron spectroscopy.
Direct Measurement of the Reactivity of NH and oh on a Silicon Nitride Surface
Authors: Buss R. J. , Ho P. , Fisher E. R. , Breiland William G.
Published: March 2011

In order to understand and successfully model the plasma processing used in device fabrication, it is important to determine the role played by plasma-generated radicals. We have used the IRIS technique (Imaging of Radicals Interacting with Surfaces) to obtain the reactivity of NH(X3∑-) and OH(X2II) at a silicon nitride film surface while the film is exposed to a plasma-type environment. The reactivity of NH was found to be zero both during exposure of the surface to an NH3 plasma and during active deposition of silicon nitride from a SiH4/NH3 plasma. No NH surface reaction was detectable for any rotational states of NH and over a surface temperature range of 300-700 K. OH radicals generated in an H2O plasma were found to have a reactivity of 0.57 on a room temperature oxidized silicon nitride surface. The OH reactivity falls to zero as the temperature of the substrate is raised.
Thermodynamic Simulation of MOCVD YBa2Cu3O7−x Thin Film Deposition
Authors: Bernard C. , Weiss F. , Pisch A. , Madar R.
Published: March 2011

Chemical Vapour Deposition of YBa2Cu3O7−x superconductors using organometallic precursor materials involves the formation of a great variety of condensed phases (oxides, carbonates, hydroxides, carbides, hydrides) and a complex gas phase. Therefore, the possibility of calculating the stability ranges of the different phases susceptible of being deposited and the influence of the main experimental parameters (precursor partial pressure, oxygen partial pressure, total pressure, temperature) is very attractive. Recently, some initial attempts have been published, but the authors did not have sufficiently complete and reliable thermodynamic data on the species involved in the process. These results will be discussed. Furthermore, a homogeneous and complete set of data for the whole system will be presented, and the reactions of the deposition process will be simulated on the basis of this data set. The most important results will be compared to the previous calculations and to recent experimental work.
Thermodynamic Constraints for the In Situ MOCVD Growth of Superconducting Tl-Ba-Ca-Cu-O Thin Films
Authors: Holstein William L.
Published: March 2011

In spite of several attempts, superconducting Tl-Ba-Ca-Cu-O thin films have not been successfully prepared in situ by metal organic chemical vapor deposition (MOCVD). Preparation of a phase by MOCVD requires that it be thermodynamically stable with respect to its decomposition into volatile species and other condensed phases. For MOCVD growth of Tl-Ba- Ca-Cu-O compounds in the presence of oxygen from reagents containing only C-H or C-H-O ligands, Tl2O(g) and TIOH(g) exhibit appreciable volatility. If reagents with ligands containing fluorine are used, the formation of volatile TIF(g) must also be considered. Thermodynamic data for these materials are compiled, and thermodynamic relationships between these gases, H2O(g) and HF(g) are established. The thermodynamic stability of TIOH(g) and TIF(g) makes the in situ growth of Tl-Ba-Ca-Cu-O compounds by MOCVD more difficult than their in situ growth by physical vapor deposition processes, for which Tl2O(g) is the only volatile TI-containing species present.
Electro-Optic Materials by Solid Source MOCVD
Authors: Hiskes R. , Dicarolis S. A. , Fouquet J. , Lu Z. , Feigelson R. S. , Route R. K. , Leplingard F. , Foster C. M.
Published: March 2011

The solid source MOCVD technique1,2, employing a single powder vaporization source composed of mixed beta-diketonate metalorganic compounds, has been used to grow thin films of a variety of electro-optic materials, including lithium niobate, strontium barium niobate, and potassium niobate. Results for potassium niobate films are quite preliminary, but indicate that a volatile potassium organometallic source can be synthesized which is useful for growing potassium niobate by MOCVD. High quality single phase (001) oriented strontium barium niobate films have been deposited which exhibit waveguiding behavior. The most extensive work has been done on lithium niobate, which has been deposited epitaxially on a variety of substrates. Oriented z-axis (001) films have been grown on c-axis sapphire with and without a (111) oriented platinum base electrode and on a bulk grown lithium niobate substrate. Films grown directly on c-axis sapphire at 700 C exhibit x-ray rocking curve linewidths as low as.044 degrees, nearly perfect in-plane orientation as determined by x-ray phi scans, and peak-to-peak surface roughness less than 40 Å. Optical waveguiding has been demonstrated by a single prism coupling technique on similar films 1175 – 2000 Å thick grown at 500 C, with optical losses of approximately 2 db/cm at 632.8 nm measured over 3.5 cm long films. Polarization vs. electric field measurements on 1100 Å thick films grown on platinum show a hysteresis loop indicating ferroelectric behavior.
MOCVD of Magneto-Optical Ceramics
Authors: Okada Masaru , Katayama Shigehisa , Kamiya Tadashi
Published: March 2011

Bismuth-substituted yttrium iron garnet, BixY1−xFe5O12 thin films have been epitaxially grown on a Gd3Ga5O12 (111) substrate at 750°C under reduced pressure (6 Torr), with a deposition rate of 20∼50nm·min−1 by MOCVD. The maximum value of Faraday rotation was −7.5×104deg·cm−1at a Bi-content of 2.5 atoms per formula unit. The Figure of unit was 14.30 deg., which is significantly larger than that obtained by sputtering. On the other hand, cerium-substituted films could not be obtained even at elevated temperatures, 900°C.
Chemical Vapor Deposition of Vanadium Oxide Tiiin Films
Authors: Stewart Ogie , Rodriguez Joan , Williams Keith B. , Reck Gene P. , Malani Narayan , Proscia James W.
Published: March 2011

Vanadium oxide thin films were grown on glass substrates by atmospheric pressure chemical vapor deposition (APCVD) from the reaction of vanadium(IV) chloride with isopropanol and t-butanol. Films were deposited in the temperature range 250 to 450°C. The as-deposited films were a dark greenish color consistent with formation of a lower oxide of vanadium. Annealing a film deposited on Corning 7059 glass in air converted the material to a yellow film. X-ray diffraction of the yellow film revealed the presence of V2O5. Optical spectra of the films are presented. Glass substrates previously coated with conductive fluorine doped tin oxide were coated with V2O5 and evaluated for electrochromic activity.
Low Temperature MOCVD of Oriented PbTiO3 Films on Si(100)
Authors: Chen H. , Yen B.M. , Bai G.R. , Liu D. , Chang H.L.M.
Published: March 2011

Highly oriented PbTiO3 (PT) thin films have been successfully grown on Si(100) using MOCVD technique at as low as 450°C. Titanium isopropoxide, Ti(C3H7O)4, tetraethyl lead, Pb(C2H5 )4, and pure oxygen were chosen as precursor materials in this work. The resulting film chemistry and texture were found to be strongly dependent on Pb/Ti source flow ratio and growth temperature.
Preparation of Ba1−xSrxTiO3 Thin Films by Metalorganic Chemical Vapor Deposition and Their Properties
Authors: Gilbert S. R. , Wessels B. W. , Neumayer D. A. , Marks T. J. , Schindler J. L. , Kannewurf C. R.
Published: March 2011

Ba1−xSrxTiO3 thin films were deposited over the entire solid solution range by low pressure metal-organic chemical vapor deposition. The metal-organic precursors employed were titanium tetraisopropoxide and barium and strontium(hexafl uoroacetylacetonate)2·tetraglyme. The substrates used were LaAlO3 and (100) p-type Si. Ba1−xSrxTiO3 films deposited on LaAlO3 were epitaxial, while the films deposited on Si showed no texture. Auger spectroscopy indicated that single phase Ba1−xSrxTiO3 films did not contain detectable levels of fluorine contamination. The dielectric constant was found to depend upon the solid solution composition x, and values as large as 220 measured at a frequency of 1 MHz were obtained. The resistivities of the as-deposited films ranged from 103 to 108 Ω-cm. Temperature dependent resistivity measurements indicated the films were slightly oxygen deficient.
Growth of (001)-Oriented Sbn Thin Films by Solid Source MOCVD
Authors: Lu Z. , Feigelson R. S. , Route R. K. , Hiskes R. , Dicarolis S. A.
Published: March 2011

By the solid source MOCVD technique, we have deposited 2000 – 3000 Å thick single phase SrxBa1−xNb2O6 (SBN) films on (100) MgO substrates using tetramethylheptanedionate (thd) sources. X-ray diffraction (XRD) 2θ scans indicated that these films were completely (001) oriented. XRD Φ scans, however, showed the films contained four in-plane grain orientations whose volume fractions could be controlled by altering the Sr/(Sr+Ba) and Nb/(Sr+Ba) ratios in the source powders. The in-plane volume fractions did not change with the deposition rate or the cooling rate. Films with composition Sr0 58Ba0.42Nb1.94O6 had mainly two in-plane orientations. Optical waveguiding behavior was demonstrated in these films. Refractive indices were found to be no= 2.20 and ne = 2.13, as compared to no = 2.31 and ne = 2.27 for bulk SBN60.
Lead Titanate Thin Films Prepared by Metallorganic Chemical Vapor Deposion (MOCVD) on Sapphire, Pt, and RuOx Substrates
Authors: Hendricks Warren C. , Desu Seshu B. , Peng Chien H.
Published: March 2011

Transparent and highly specular PbTiO3 thin films were deposited on sapphire, platinum and ruthenium oxide-coated silicon wafers by hot-wall metallorganic chemical vapor deposition (MOCVD). Lead bis-tetramethylheptadionate and titanium ethoxide were used as chemical precursors. Films were deposited over a range of experimental conditions. X-ray diffraction (XRD) was used to determine the phases present in the films; Scanning Electron Microscopy (SEM) was used to examine the surface morphology and Energy Dispersive Spectroscopy (EDS) was used to determine the composition. Optical spectra were obtained to confirm the highly dense and transparent nature of the films. The chemical stability of the ruthenium oxide substrates in the MOCVD environment as well as the existence of a high-temperature deposition regime for composition control are also discussed.
Partition of alloying elements on eutectic solidification of cast iron
Authors: Kagawa Akio , Okamoto Taira
Published: March 2011

The coefficients for partition of an alloying element (X) between austenite and liquid iron (), and between eutectic liquid and its solid (PS and PM in the stable and metastable eutectic solidifications, respectively) have been investigated thermodynamically. The coefficient depended significantly on the interaction between carbon and the element X. A simplified method for the evaluation of was introduced from the thermodynamic analysis of factors influencing on . The coefficients, PS and PM, calculated from and the coefficient for partition of the element X between cementite and ausfenite, agreed well with those obtained experimentally. It was indicated from the thermodynamic stability for the coexisting phases that the effect of an alloying element on graphitization occurring during eutectic solidification wvs closely related to the values of Δ(+PM-PS and and also to the effect of the element on the difference between the stable and metastable eutectic temperatures. No strict relation was found between the effects of an alloying element on the carbon activity in liquid iron and on the graphitization.
The Relation between Porosity and Solidification Mechanism in Grey Cast Iron
Authors: Hillert Mats
Published: March 2011

The factors resulting in porosity in various types of cast iron were fairly well understood by 1960. These factors are now reviewed. The importance of the details of the solidification sequence is stressed and the special features of the eutectic reaction in nodular cast iron are emphasized.
Graphite Morphology in Cast Irons
Authors: Loper Carl R.
Published: March 2011

Graphite structures formed during the cooling of molten cast irons and during their solidification were examined in alloys as a function of composition, treatment (magnesium and/or rare earths) and inoculation. The effect of cooling rate and solidification conditions on the morphology of the resultant graphite was investigated using a variety of techniques (optical and scanning electron microscopy, etching procedures, etc.) to reveal the growth characteristics of this phase and its relationship to other phases developing during the solidification process. These graphite forms have been classified according to their morphology and the factors affecting their development. Examples of these graphite forms are presented and their growth conditions and charateristics analyzed.

Kish graphite is shown to form, not as a result of internal development in a melt and subsequent flotation to the surface, but by a surface growth mechanism forming extensive graphite plates. Proeutectic graphite also forms in the melt just prior to the appearance of the eutectic, however, its growth in the absence of austenite is shown to be limited.

While a variety of graphite morphologies have been identified in eutectic solidification, it is shown that these graphite shapes may develop from the same nucleation sites, that growth conditions determine the graphite morphology, and that as the growth conditions are altered the morphology of the resultant graphite is correspondingly affected. The transition between graphite shapes such as flake, compacted, spheroidal, exploded, etc. is depicted in various microstructures.

In addition, the relationship between certain compounds (e.g., titanium carbo-nitride, etc.) and graphite growth is demonstrated and discussed.
Formation and Prevention of Chunky Graphite in Slowly Cooled Nodular Irons
Authors: Xi Tang Chong , Fargues J. , Hecht M. , Margerie J. C.
Published: March 2011

An experimental device has been designed in order to simulate the solidification of large castings by means of a small-sized sample (1 kg). Once the spheroidizing and inoculation processes have been completed, this sample is slowly cooled at controlled rate and under protective atmosphere in an insulated crucible placed in a laboratory resistance furnace. The maximum freezing time is about 90 min. These tests relate to a base iron having a good degree of purity.

SEM, optical microscopy and automated electron microprobe have been used for studying structure and mechanism of chunky graphite formation.

Results of over forty tests confirm several data abstracted from literature and provide some more information. For instance, there are different ways of preventing chunky graphite formation : acceleration of solidification, use of Ni-Mg or pure Mg as spheroidizers and, in any case, an antimony addition (0,02%).

A rather low carbon equivalent is also a favourable factor. However, for a given carbon equivalent, a final relatively high Si content improves graphite spheroidizing, chunky graphite appearing only if this content results from Fe-Si-Mg additions and/or from overinoculation.

Besides, confirmation is given of the detrimental effect of useless rare earth additions (e.g. 0,02%).

The matrix surrounding chunky graphite is on average more rich in Si than the one surrounding spheroidal graphite. An oxidizing etching reveals that chunky eutectic has formed at first.

Aiming an interpretation of the results, structure examination keeps going on, in order to find out if there could be several kinds of chunky graphite.
Impurity Incorporation During Si Ultrafast Solidification to the
Crystalline and Amorphous Phase
Authors: Ugo Campisano Salvatore
Published: March 2011

Impurity segregation at the liquid-solid interface, interfacial
instabilities due to constitutional supercooling and precipitation are
compared for the growth of a crystalline or of an amorphous phase from rapid
solidification. Segregation at low concentration and interfacial
instabilities at high concentrations are shown to give the same information.
The impurity behaviour shows a distinct similarity between the crystalline
and amorphous phases.
Fundamental Aspects of High Speed Crystal Growth from the
Melt
Authors: Cullis A.G.
Published: March 2011

Advances in the study of high speed crystal growth from the melt are
reviewed, with special emphasis on the fast melting and solidification of
silicon achieved by use of Q-switched laser radiation pulses. Rapid melting
of amorphous Si is confirmed to yield a liquid undercooled by several
hundred Kelvins and, under suitable conditions, explosive crystal growth
processes can occur. The latter involve the self-sustaining propagation of
melt bands buried within the initially amorphous material. When the highest
quench-rate conditions are established melting of even crystalline Si can
yield a final amorphous solid phase. This breakdown in crystal growth is
orientation dependent and can give regimes of crystal defect formation when
amor-phization does not take place. The processes which characterize this
limiting growth behaviour are discussed.
A Test of Two Solute-Trapping Models
Authors: Aziz M. J. , Tsao J. Y. , Thompson M. O. , Peercy P. S. , White C. W. , Christie W. H.
Published: March 2011

Two solute trapping models are compared. They are shown to predict identical
behavior at any given end of a phase diagram but different behavior as the
phase diagram is traversed. The segregation behavior of dilute solutions of
Ge in Si (ke < 1) and of Si in Ge (ke > 1) during regrowth from
pulsed-laser melting is being studied using transient conductance, high
resolution RBS, and SIMS. Our results to date suggest a significant amount"
of solute trapping (k —> 1) of Ge in Si and of Si in Ge. Such a result
would be inconsistent with the predictions of one of the models.
Modeling of Undercooling, Nucleation, and Multiple Phase Front
Formation in Pulsed-Laser-Melted Amorphous Silicon
Authors: Wood R. F. , Geist G. A. , Solomon A. D. , Lowndes D. H. , Jellison G. E.
Published: March 2011

Recently available experimental data indicate that the solidification of
undercooled molten silicon prepared by pulsed laser melting of amorphous
silicon is a complex process. Time-resolved reflectivity and electrical
conductivity measurements provide information about near-surface melting and
suggest the presence of buried molten layers. Transmission electron
micrographs show the formation of both fine- and large-grained
polycrystalline regions if the melt front does not penetrate through the
amorphous layer. We have carried out extensive calculations using a newly
developed computer program based on an enthalpy formulation of the heat
conduction problem. The program provides the framework for a consistent
treatment of the simultaneous formation of multiple states and phase-front
propagation by allowing material in each finite-difference cell to melt,
undercool, nucleate, and solidify under prescribed conditions. Calculations
indicate possibilities for a wide variety of solidification behavior. The
new model and selected results of calculations are discussed here and
comparisons with recent experimental data are made.
Low-Energy, Pulsed-Laser Irradiation of Amorphous Silicon:
Melting and Resolidification at Two Fronts
Authors: Sinke W. , Saris F.W.
Published: March 2011

After low-energy pulsed-laser irradiation of Cu-implanted silicon, a
double-peak structure is observed in the Cu concentration profile, which
results from the occurrence of two melts. From Cu surface segregation we
calculate the depth of the surface melt. Cu segregation near the position of
the amorphous-crystalline interface gives evidence for a self-propagating
melt, moving from the surface region towards the crystalline substrate.
Measurements of As-redistribution and of sheet resistance as a function of
laser energy density in As-implanted silicon are consistent with the
crystallization model which is derived from the effects as observed in
Cu-implanted silicon.

The results imply a large difference in melting temperature, heat
conductivity and heat of melting between amorphous silicon and crystalline
silicon.
Overheating and Undercooling in Silicon During Pulsed-Laser
Irradiation
Authors: Larson B. C. , Tischler J. Z. , Mills D. M.
Published: March 2011

We have used time-resolved x-ray diffraction measurements of thermal
expansion induced strain to measure overheating and undercooling in
<100> and <111> oriented silicon during pulsed laser melting and
regrowth. 249 nm (KrF) excimer laser pulses of 1.2 J/cm2 energy
density and 25 ns FWHM were synchronized with x-ray pulses from the Cornell
High Energy Synchrotron Source (CHESS) to carry out Bragg profile
measurements with ±2 ns time resolution. Combined overheating and
undercooling values of 120 ± 30 K and 45 ± 20 K were found for the
<111> and <100> orientations, respectively, and these values
have been used to obtain information on the limiting regrowth velocities for
silicon.
Characterization of Defects in Proton-Implanted
GaAs
Authors: Jenkinson H. A. , Maracas G. N. , O'Tooni M. , Sarkis R. G.
Published: March 2011

Studies have been made of n+-GaAs implanted with 300 keV protons
to fluences of 1014−1016/cm2. Electrical
studies included I–V analysis, DLTS, and thermally stimulated current
measurements made on implanted FET-like structures fabricated from MBE GaAs
epi-layers. Optical infrared reflectance spectra and high resolution
transmission electron micrographs were obtained for as-implanted material
and for specimens annealed at 300 °C and 500 °C. Results show as-implanted
material can be characterized by a band of traps lying about 0.2 eV below
the conduction band with a relatively uniform distribution throughout the
implanted region. Thermal processing causes a significant alteration in the
density and distribution of these defects.
Chemical Reaction Products from Interaction of High-Energy Beams
with Composites
Authors: Perkins J. S. , Lin S. S. , Wong P. W. , Jaklitsch D. J. , Connolly A. F.
Published: March 2011

In a study to examine the effect of irradiating a number of silica- and
carbon-reinforced composites with high-energy beams, surface analytical
techniques have proved especially effective in revealing reactions between
undoped or doped matrices and silica or carbon reinforcements,
respectively.
Improving the Quality of a Heteroepitaxial CaF2
Overlayer by Rapid Post Annealing
Authors: Pfeiffer Loren , Phillips Julia M. , Smith T.P. , Augustyniak W. M. , West K. W.
Published: March 2011

We show that post anneals of short duration at high temperature can markedly
improve the quality of CaF2 films grown by molecular beam epitaxy
(MBE) on Si (100). Anneals at 1100°C for 20 sec in an Ar ambient improved
χmin, the ratio of backscattered 1.8 MeV He4 ions
in the aligned to random direction, from as-grown values of .07 to .26, to
post post-anneal values of .03 to .045. This is the best χmin yet reported
for the CaF2:Si system. The post-annealed films also show
improved resistance to chemical etching and mechanical stress, and increased
dielectric breakdown voltages.
Transient Processing of Titanium Silicides in a Non-Isothermal
Reactor
Authors: Wei C.S. , Van Der Spiegel J. , Santiago J. , Seiberling L.E.
Published: March 2011

Transient processing of titanium silicides on single-crystal Si in a
non-isothermal reactor provides high quality films. Heat from quartz-hal?gen
tungsten lamps and a small temperature gradient act as driving forces for
the reaction. The temperature gradient, small compared to the concentration
gradient, shows negligible influence on the formation process. The influence
of sample reflectivity on the other hand is appreciable. From Xe+ marker
experiments, Si atoms are found to be the moving species either up or down
the temperature gradient. Small amount of TiSi as an intermediate phase is
found to be coexistent with TiSi2. The silicide formation of the implanted
wafers is somewhat slower than that of the unimplanted wafers.
Incoherent Light Annealing of Selectively Implanted GaAs for
Mesfet Applications
Authors: Kitching S.A. , Badawi M.H. , Bland S.W. , Mun J.
Published: March 2011

Capped and capless incoherent light annealing of high and low dose silicon
implants into GaAs have been compared with conventional capless furnace
annealing of the same implants. The yield and uniformity of DC
characteristics of selectively implanted depletion mode MESFET's fabricated
on 2-inch wafers annealed by the above three methods have also been
compared. Capped incoherent light annealing was found to give results
comparable to and in some cases better than conventional furnace annealing
both in terms of activation of the implants and also device performance.
Rapid Thermal Annealing of Deposited Sio2 Films
Authors: Wong J. , Lu T.-M. , Cohen S.S. , Mehta S.
Published: March 2011

Silicon dioxide films have beep deposited at an oxygen pressure and
substrate temperature as low as 10−2 Pa and 300°C, respectively,
using a partially ionized nozzle-beam technique. The refractive index of the
film is equal to that of the thermally grown silicon dioxide film, but a
frequency shift was obsrved in the infrared absorption peak at 1045 cm as
compared to 1080 cm−1 of the thermally grown silicon dioxide
film. This frequency shift disappeared after the deposited film was annealed
in a rapid thermal annealing system utilizing an incoherent light source. We
emphasize that from the standpoint of device fabrication, although the
annealing temperature is high (%1100°C), the time is very short (seconds),
so that this process is still compatible to the requirementsof low
temperature processing. Effects of rapid thermal annealing on LPCVD and
PECVD oxides are also studied and the results are compared to that of the
oxide deposited by the partially ionized nozzle-beam technique.
Channeling Effect in Boron and Boron Molecular
Ion-Implantation
Authors: Delfino N. , Paine B.M.
Published: March 2011

The extent of boron channeled into interstitial and substitutional sites is
measured for singly charged ions of B, BF, BCl, and BF2 implanted
into <100> silicon. We find that the most deeply penetrating boron
atoms ome to rest in interstiitial sites with the consequence that
electrical junctions are always more shallow than etallurgical junctions.
This result is essentially independent of ion mass, energy, and fluence.
Recent Advances in Si And Ge Zone-Melting Recrystallization
Authors: Chen C. K. , Gels M. W. , Choi H. K. , Tsaur B-Y. , Fan John C. C.
Published: March 2011

By improving the thermal uniformity and stability of our graphite-strip-heater oven, we have been able to significantly improve the overall quality of ZMR Si films. We have observed unbranched subboundaries and new types of defects that are less extended than the usual sub-boundaries. The overall wafer flatness has been improved so that total warp is less than 4 μm for 3-inch wafers. We have also utilized the ZMR technique for producing thin Ge-on-insulator films.