bluuebunny/crossref_metadata_2025 huggingface dataset:
Amorphous Silicon-Based Superlattices and their Potentials to Device Applications
Authors: Hirose Masataka , Murayama Naoki , Miyazaki Seiichi , Ihara Yohji
Published: March 2011

Two types of amorphous silicon (a-Si:H)/silicon nitride (a-Si3 N4 :H) multilayers have been prepared either by turning-off the plasma at each step of individual layer growth (step by step deposition) or by quick gas switching without interrupting the plasma (continuous deposition). It is found that the continuous deposition causes a significant mixing of nitrogen into the a-Si:H well layers and deteriorates the compositional abruptness in the a-Si:H/a-Si3N4 :H interface. Also, undesirable incorporation of nitrogen into the a-Si:H well layers tends to induce nonradiative recombination centers near the interface.
Carrier Separation Effects in Doping Modulated Amorphous Silicon
Authors: Kakalios J. , Tsai C. C. , Street R. A.
Published: March 2011

Doping modulated amorphous silicon films have been synthesized which exhibit photoconductivity decay times in excess of 1000 seconds at 78 K. The time and intensity dependence of the photoconductivity is described by a model in which photo-excited charge carriers are spatially separated to separate layers by the built-in pn junction fields and reside in band tail states.
a-SiGe:H Alloy and its Application to Tandem-Type Solar Cell
Authors: Yukimoto Y. , Aiga M.
Published: March 2011

Amorphous SiGe:H alloy is the key material in achieving high conversion efficiency with tandem-type amorphous silicon alloy solar cells. Status and issues for this key material are discussed, and efforts made to irprove it are reviewed to obtain directions for higher quality a-SiGe:H alloys. An application of the improved alloy to tandem-type solar cell to achieve 9.6% efficiency for the cell size of 100 cm2 is reported.
High Quality a-Si Films and Superlattice Structure p-Layer a-Si Solar Cells
Authors: Nakano Shoichi , Tsuda Shinya , Tarui Hisaki , Takahama Tsuyoshi , Haku Hisao , Watanabe Kaneo , Nishikuni Masato , Hishikawa Yoshihiro , Kuwano Yukinori
Published: March 2011

As a new preparation method for high-quality a-Si films, we have developed the super chamber, a separated UHV reaction chamber system. A low impurity concentration and excellent film properties were obtained by the super chamber. A conversion efficiency of 11.7% was obtained for an a-Si solar cell using a high-quality i-layer deposited by the super chamber, and a p-layer fabricated by a photo-CVD method.

As a new material, amorphous superlattice structure films were fabricated by the photo-CVD method for the first time. Quantization effects and low damage to the interfaces were observed. Superlattice structure p-layer a-Si solar cells were fabricated for the first time, and a conversion efficiency of 10.5% was obtained.
Effects of Light Soaking Conditions on Thin Film Silicon:Hydrogen Alloy Solar Cells
Authors: Willett D. R. , Tanner D. P. , Mchenry G.
Published: March 2011

Variation of environmental conditions during light soaking of thin film silicon:hydrogen alloy (TFS) solar cells can have measurable effect on durability. Such sensitivity must be considered in optimizing processes for maximizing long-term performance. This paper will describe the effects of operating temperature, light intensity, operating bias, and duration of light soaking on the stability of TFS p-i-n solar cells.
Double Injection Field Effect Transistor A New Type of Solid State Device
Authors: Hack M. , Shur M. , Czubatyj W.
Published: March 2011

We propose a new general principle of operation for solid state devices, and demonstrate a novel transistor which we call a Double Injection Field Effect Transistor, based on this principle. We have fabricated amorphous silicon alloy double injection transistors, operating on the modulation of a double injection current by a gate field covering the complete path of the current channel.

Using these amorphous silicon alloy double injection transistors, we have achieved currents over fourteen times those theoretically possible for conventional amorphous silicon field effect transistors operating under similar conditions. This new principle, applicable to both thin film amorphous and crystalline devices, offers the potential of high current, high speed field effect transistors.
Thin Multi-Layered Photoreceptor Deposited From Disilane
Authors: Araki S. , Nou H. , Kamaji H. , Kiyota K.
Published: March 2011

A thin multi-layered photoreceptor drum has been fabricated, using glow-discharge decomposition of disilane. The photoreceptor is thin(10 μm), but it is charged up sufficiently. The photoreceptor has three layers; the p-type a-Si:H (blocking layer), the intrinsic B-doped a-Si:H (photoconductive layer) and a-SiC:H (passivation layer). Disilane is highly reactive. The intrinsic B-doped a-Si:H was prepared from a slightly gaseous mixture of B2H6 (3 ppm). The amorphous-SiC:H passivation layer deposited from Si2H6 and C3H8 was developed to achieve sufficient surface potential and to improve the environmental characteristics.
Reactive Deposition of a-Silicon and Si-Based Alloys
Authors: Hanna J. , Oda S. , Shibata H. , Shirai H. , Miyauchi A. , Tanabe A. , Fukuda K. , Ohtoshi T. , Tokuhiro O. , Nguyen H. , Shimizu I.
Published: March 2011

High photoconductive a-Si:H(F) and St-based alloys were prepared from “precursors” made by oxidation of silane with F2 or reduction of SiFn (n=1,2,) with atomic hydrogen. Both crystalline and amorphous silicon were prepared at will, in the latter case, by controlling the flow of hydrogen. A marked reduction in the localized states in the vicinity of valence band was eatablished in the a-Si:H(F) prepared under optimal condition. A novel photoconductive film with high photoconductive gain for near-tr light was successfully made by multiplying a-Si:H/a-SiGe:H(F) periodically by a new preparation technique without a rise in the dark conductivity.
Wafer Characterization of an Epi Reactor Using Sheet Resistance Mapping
Authors: Johnson Walter H. , Keenan W. Andrew , Smith Alan K.
Published: March 2011

Sheet resistance mapping has become an indispensable tool in characterizing ion implanters for both integrated circuit manufacturers and equipment manufacturers. The sheet resistance mapping technique is now being extended into additional applications such as the characterization of metal deposition, CVD, and epitaxial silicon growth. This technique has become especially necessary with the advent of 150mm and 200mm wafers, where 5 or 9 site measurements cannot provide sufficient data essential for process control.

In order to optimize the performance of an epi reactor it is necessary to control and characterize the gas flows and temperature distributions inside the reactor. The control of these variables is essential for thickness and resistivity uniformity in epi layers. This paper describes the use of sheet resistance profiles and contour maps to study the resistivity and thickness uniformity variations in an epi reactor. The sheet resistance maps allow for control of the epi process without requiring data from other test sources.This ensures real time process control for production, as well as very rapid feedback for maintenance while doing equipment repair.
Defects Characterization of Arsenic Implanted Silicon by Ac Hall Effect Measurements
Authors: Jaouen H. , Ghibaudo G. , Christofides C.
Published: March 2011

AC and DC Hall effects measurements as a function of temperature (77-300K) and frequency ( 1Hz-100KHz) have been performed to characterize Implanted Silicon films. This technique enables the determination of the annihilation processes of defects In such layers as a function of temperature of isochronal anneallngs (300°C to 1100°C during 1 hour). The experimental results are discussed with respect to proper transport models based on short and long range disorder considerations in order to find out the features of defects and Inhomogeneities arising from implantation and their thermal annihilation after isochronal annealing.
The Formation of Highly Conductive Shallow Junction Layers in (100) Siliconl By Gallium Ion Implantation
Authors: Harrison H.B. , Li Y.H. , Sai-Halasz G.A. , Iyer S.
Published: March 2011

This paper presents the results obtained from a comparative study of ion implanted Gallium (Ga) into (100), n type Silicon. A comparison is made between long time (≥ 30 mins) furnace annealed and Rapid Thermally Processed (RTP), 100keV implants of 1 and 3×10l5/cm2 doses of Ga. The results show that for RTP an extremely high substitutional concentration of Gallium, in excess of 3×1020/cm3 can be obtained with approximately 100% electrical activation, resulting in highly conductive very shallow p type layers.
Silicon Transport in Lateral Silicide Growth of CrSi2
Authors: Zheng L. R. , Doolittle L. R. , Mayer J. W.
Published: March 2011

Silicide formation and growth are studied in three geometries: conventional planar thin films, lateral diffusion couples formed by depositing metal layers on Si islands, and device geometry couples formed by depositing metal on oxide-patterned Si substrates. The influence of impurities is studied by implanting arsenic and krypton into conventional and device geometry structures.

Here we present growth kinetics of CrSi2 where the presence of impurities has a strong influence. Si transport dominates in disilicide formation and leads to erosion of contacts around the periphery of oxide windows. Implantation of arsenic suppresses CrSi 2 formation; with krypton implantation, the growth kinetics shifts from linear to square-root in character. We attribute these results to impurity segregation at interfaces or grain boundaries.
Characteristics of Selective Lpcvd W Films By Silicon Reduction
Authors: Joshi R. V. , Smith D. A.
Published: March 2011

The characteristics of Selective LPCVD tungsten films produced by silicon reduction of tungsten hexafluoride are presented. The tungsten films deposited using Si(100), Si(111) and polysilicon undoped and doped substrates are analyzed by X-RAY, TEM, RBS, AES, SIMS and SEM. The as deposited bcc tungsten films are polycrystalline with a grain size 80 - 100Å. The effect of annealing temperature and time on the crystal structure of films was studied. Tungsten reacts to form tungsten silicide at 600°C. The silicide grain size is of the order of 100 - 200Å at 600°C and increases gradually to 400 - 500Å at 1000°C. The oxygen impurities in the film retard the silicide formation further at 1000°C. Silicon from the substrate out-diffuses to the film surface and reacts with the presence of oxygen impurities in the annealing ambient to form Si-O at 1000°C. As deposited film resistivities of 130-140 micro-ohm-cm are achieved reproducibly and reach 60-70 micro-ohm-cm after 1000°C annealing in nitrogen or argon ambient. The impurities H, C, O and F are found in the as deposited films.
Recrystallization of Oxygen Contaminated Al Films
Authors: Kolk G.J. Van Der , Verkerk M.J.
Published: March 2011

Al was evaporated at oxygen partial pressures, PO2, varying between 10−7 and 10−4 Pa on substrates of silicon nitride. The substrate temperature was varied between 20 °C and 250°C. The films were annealed at temperatures up to 500°C.

For Al films deposited at 20°C, it was found that the average grain size decreases with increasing oxygen partial pressure. After annealing recrystallization was observed. The relative increase of grain size was less for higher values of pO2. Annealing gave rise to a broad grain size distribution.

For Al films deposited at 250°C, the presence of oxygen caused the growth of rough inhomogeneous films. This inhomogeneous structure remained during annealing.
Time Resolved Tem of Laser-Induced Phase Transitions in a-Ce And a-Si/Al-Films
Authors: Bostanjoglo O. , Endruschat F. E. , Tornow W.
Published: March 2011

This paper presents an improved new method for studying the dynamics of laser induced phase transitions down to the submicron-nanosecond scale by means of a modified commercial Transmission Electron Microscope (TEM) /1/. Results on Pulsed Laser Annealing (PLA) of amorphous Germanium and a-Si/Al films are described. Potential applications and limits of this method are briefly discussed.
Stresses in Gatelevel Interconnects of Wsi2 AND TaSi2
Authors: Townsend P. H. , Fulks R. T. , Plas H. A. Vander , Ho J.
Published: March 2011

Stresses in WSi2 films prepared by chemical vapor deposition have been examined using an optically levered laser beam during typical processing cycles to 900 C. Initial heating produces tensile stress levels of 1.0 GPa at 500 C with crystallization into the inetastable hexagonal form. Cooling from this temperature results in room temperature stresses of 1.2 GPa. A large decrease in the tensile stress level accompanies the transformation into the stable tetragonal structure during heating from 500 C to 750 C. Films in this form are mechanically stable and respond elastically to further thermal cycling.

Films of TaSi2 sputtered from an intermetallic target and co-sputtered from elemental targets have also been investigated. Initial heating of films sputtered from the intermetallic target produces a tensile stress state during crystallization which is high but slightly less than observed during crystallization of WSi2. This high tensile state is not observed in films deposited in layers from elemental targets. The appearance of a metastable phase is not observed for intermediate anneals in either case. The initial crystallization results in the stable phase of hexagonal TaSi2. Fully annealed films are elastic below 920 C.
Transient Scanning Electron Beam Annealing Methods Used to Study Diffusion and Defects in Implanted Silicon
Authors: Hart Michael J. , Evans Alan G. R. , Amaratunga Gehan A. J.
Published: March 2011

Rapid thermal annealing of arsenic and boron difluoride implants, such as those used for source/drain regions in CMOS, has been carried out using a scanning electron beam annealer, as part of a study of transient diffusion effects. Three types of e-beam anneal have been performed, with peak temperatures in the range 900-1200°C; the normal isothermal e-beam anneals, together with sub-second fast anneals and ‘dual-pulse’ anneals, in which the sample undergoes an isothermal pre-anneal followed by rapid heating to the required anneal temperature in less than O.5s.

The diffusion occuring during these anneal cycles has been modelled using SPS−1D, an implant and diffusion modelling program developed by one of the authors. This has been modified to incorporate simulated temperature vs. time cycles for the anneals. Results are presented applying the usual equilibrium clustering model, a transient point-defect enhancement to the diffusivity proposed recently by Fair and a new dynamic clustering model for arsenic. Good agreement with SIMS measurements is obtained using the dynamic clustering model, without recourse to a transient defect model.

Defects remaining in diodes fabricated with the forementioned implants after these anneal cycles have been studied using DLTS techniques. Trap densities for the three types of e-beam anneal are comparable to those for furnace annealed diodes, as are the reverse leakage currents measured (typically 2–5nA for a 0.85mm2 diode at -5V).
XeCl Excimer Laser Annealing Used to Fabricate Poly-Si Tfts
Authors: Sameshima T. , Usui S.
Published: March 2011

Mo-gate n-channel poly-Si TFTs have been fabricated for the first time at a low processing temperature of 26°C. 500 to 1000A thick a-Si:H was successfully crystallized by pulsed XeCl excimer laser (308nm) annealing without heating the glass substrate. The channel mobility of the TFT was 180 cm2/V.sec when the a-Si:H was annealed at energy density of 200 mJ/cm2.
Effect of Polysilicon Deposition and Thermal Cycling on Thin Oxide Quality
Authors: Wu N.R. , Chiao S. , Bhushan B. , Batra T. , Fan S.K. , Pizzo P. , Yang C.Y.
Published: March 2011

A scaled-down MOS transistor requires high-quality thin gate oxide (∼100 Å) as in tunnel oxide for an EEPROM device. Instead of investigating the lower (SiO2/Si) interface properties, we study the upper (poly-Si/SiO2) interface as affected by poly deposition conditions, phosphorus doping, and thermal cycling. The results show that prolonged or high-temperature heat treatment will degrade thin oxide quality. The initial V-t slope derived from constant-current stressing data is used to assess oxide quality.
Model of Porous Silicon Oxidation
Authors: Ore F. R. , Harwood P. B.
Published: March 2011

A two-dimensional model for simulating the growth of SiO2in a porous Si layer is described. The model makes use of rapid early oxidation based on the presence of micropores in the oxide normal to the growing oxide-oxidant inter- face. With initial pore shape, ambient pressure and oxidation temperature as inputs, the model predicts the final morphology of the grown oxide film and calculates the refractive index and other key indicators of oxide quality. The model is a first step towards allowing the design of optimized processes for formation of high-integrity oxidized porous Si layers.
Dlts Ciiaracterizati oh of Precipitation Induced Microdefects
Authors: Whitwer F.D. , Haddad H. , Forbes L.
Published: March 2011

Capacitance DLTS measurements have been performed on heavily precipitated n— and p—type silicon wafers. The results indicate heavy metal gettering with a mid-bandgap deep level (0.55eV) for n—type silicon. The results for p—type siliconshow a band of states present in the lower half of the bandgap. This band of states correlates well to the band of allowed energies found in heavily dislocated p—type silicon.
Fast Zerbst Transient Analysis and Application to Intrinsic Gettered P—type Epitaxial Wafers
Authors: Aminzader M. , Forbes L.
Published: March 2011

One of the principal difficulties in applying the Zerbst analysis to MOS capacitor transient recovery is the extremely long retention time of the MOS capacitor in high lifetimematerials. Typically the retention time is thousands of seconds at room temperature, so long times are required for a significant number of measurements. Furthermore, extrapolating the result of high temperature measurements back to room temperature can lead to large errors. A modified C—t transient response using a step from accumulation to depletion followed by light and then a small step from inversion to stronger inversion speeds up the generation lifetime measurement and separates the surface generation from the bulk generation. Pre— and post—epitaxial intrinsically gettered p/p+ wafers were subjected to high temperature CMOS process simulation and MOScapacitors with Al dots and guard rings were fabricated. Generation lifetime of about 5 msec were measured using the modified fast Zerbst method on properly intrinsically gettered epitaxial wafers, particularly the pre—epitaxial intrinsically gettered wafers.
Spinel Formation from Magnesium Aluminium Double Alkoxides
Authors: Jones Kenneth , Davies Thomas J. , Emblem Harold G. , Parkes Peter
Published: March 2011

Double alkoxides of the general formula Mg[Al(OR)4]2 where R is iso-Pr or sec-Bu were prepared by reacting aluminium and magnesium metals together with the alcohol ROH and purified by vacuum distillation. They were characterised by IR, proton and 27Al NMR spectroscopy and MW determination. A magnesium aluminium double alkoxide was also prepared by treating the commercially available aluminium alkoxide ‘Aliso B’ [a mixed aluminium (iso-propoxide)(sec-butoxide)] with magnesium and iso-propanol. Treatment of magnesium aluminium double alkoxides with water and an alkanolamine (preferably triethanolamine) gives a rigid coherent gel. Viscosity measurements and 27Al NMR spectroscopy suggest that the double alkoxide does not break down to its constituents during hydrolysis. The air-dried gel was shown by XRD to convert quantitatively to spinel on firing to 1500°C. The resistance of the double alkoxide moiety to hydrolysis explains the ease of conversion to spinel on firing. The gel has been used to bind alumina and magnesia grain. Gels suitable for binding refractory grain were obtained only when the alkanolamine content corresponded to one alkanolamine group per metal atom. Electron micrographic and XRD studies showed that in fired refractory pieces, the bonding phase was spinel.
Synthesis of Oxide Ceramic Powders by Aqueous Coprecipitation
Authors: Moyer J. R. , Prunier A. R. , Hughes N. N. , Winterton R. C.
Published: March 2011

Aqueous precipitation in a computer-controlled continuous crystallizer has been applied to the preparation of cordierite, mullite, alumina, and zirconia precursor powders. The particles are dense, spherical, and x-ray amorphous. The powders have a particle size range of 0.2–5 μm and a surface area of 1 – 10 m2/g The properties of the powders and of some green and fired pieces are described.
Prolonged Chaotic Oscillations During the Gel/Xerogel Transition in Silicon Tetramethoxide Polymerization as Detected by Pyrene Excimerization.
Authors: Kaufman Vered R. , Avnir David
Published: March 2011

When the polymerization of Si(OCH3)4is carried out in the presence of surface active agents, prolonged oscillations (over 1000 hrs) at the gel/xerogel transition are observed. The oscillations are of large amplitude, they are slow (several hrs/period), and they exhibit a chaotic behaviour. The probe by which these oscillations are observed is emission from excited state monomeric and excimeric pyrene. It is suggested tentatively that the driving forces for this oscillation are the structural relaxation of the secondary polymeric gel structure and the dispersion of adsorbed pyrene to thermodynamically favored adsorption sites. Relevant models could be those of oscillatory sol/gel phase transitions and of oscillatory polymerization reactions. We are unaware of previous observations of oscillations in sol/gel systems.
Silicon −29 Solids NMR-MAS Characterization of Non-Oxide Powders and Fibers
Authors: Inkrott Kenneth E. , Wharry Stephen M. , O'Donnell Dan J.
Published: March 2011

Powder x-ray diffraction has been the most common method for rapid structural analysis and identification of crystalline ceramic raw materials. However, new structural ceramic raw materials often have linebroadened or featureless XRD patterns due to structural strain or small crystallite size. Characterization of various silicon carbide and silicon nitride powders and ceramic fibers by Si-29 NMR-MAS spectroscopy has revealed structural details and differences in these materials previously indistinguishable by XRD or other routine methods. Unique variables intrinsic to a given ceramic synthesis process are reflected in the NMR-MAS spectra of the resulting products.
Synthesis of High Purity Silica Glass from Metal Alkoxide
Authors: Su S. R. , Onorato P. I. K.
Published: March 2011

High purity silica was synthesized by hydrolytic decomposition of tetramethylorthosilicate (TMOS), followed by polycondensation, supercritical drying and sintering. The key factors which govern the hydrolysis and polycondensation were systematically studied. Gas chromatography/mass spectrometry was used to monitor the hydrolysis rate. The hydrolysis of TMOS is the only reaction at ambient temperature in an acidic environment. The rate of polycondensation was also controlled by temperature as well as pH. The structural transformation from alkoxide to gel network and to glass was illustrated by FTIR. The structure of the TMOS derived supercritically dried gel sintered at 1000°C is identical to that of silica. The shrinkage kinetics and microstructural development of the gel heated at different temperatures was examined by dilatometry, B.E.T., TGA, and STEM. This combination of techniques showed that structural relaxation is not an important factor in the densification of these gels. Below 1000°C most shrinkage is due to condensation and water evolution. Above 1000°C, viscous sintering is the primary mechanism for shrinkage.
A Molecular Building-Block Approach to the Synthesis of Ceramic Materials
Authors: Klemperer W. G. , Mainz V. V. , Millar D. M.
Published: March 2011

Ceramic materials are generally prepared from structurally simple starting materials, with the consequence that structural properties are difficult to control on a molecular level. This difficulty might be addressed by following the approach taken in polymer chemistry in which molecular building blocks are first prepared and then polymerized in a subsequent step. In the present case, the polysilicic acid esters [Si2O](OCH3)6, [Si3O2](OCH3)8, and [Si8O12](OCH3)8 are prepared and then polymerized by hydrolysis/condensation. Silicon-29 solution nuclear magnetic resonance (NMR) spectroscopy is used to estimate the extent to which the molecular frameworks of these monomers are retained during the course of hydrolysis and condensation.
Pyrolysis of Organosilicon Gels to Silicon Carbide
Authors: Fox Joseph R. , White Douglas A. , Oleff Susan M. , Boyer Robert D. , Budinger Phyllis A.
Published: March 2011

Sol-gel precursors to silicon carbide have been prepared using trifunctional chloro and alkoxysilanes which contain both the silicon and carbon necessary for SiC formation. Crosslinked gels having the ideal formula [RSiO1 5].]n have been synthesized by a hydrolysis/condensation scheme for a series of saturated and unsaturated R groups. The starting gels have been characterized by a variety of elemental analysis, spectroscopic and physical measurements including IR. XRD. TGA.. surface area and pore volume. A particularly powerful method for characterizing these gels is the combination of 13C and 29 Si solid state NMR which can provide information about the degree of crosslinking as well as residual hydroxy/alkoxy content.

The controlled pyrolysis of these gels has been used to prepare silicon carbide-containing ceramic products with surface areas in excess of 600m2/gm. The pyrolysis products are best described as a partially crystalline, partially amorphous mixture of β-SiC, silica and carbon. The effect of carbon chain length and the degree of unsaturation in the R group on the composition and surface area of the product has been determined. The origin of the high surface area of the pyrolysis products has been identified and its implications on potential uses of these materials is discussed.
Thermal Conversion of Preceramic Polysilazanes to Si3N4: Characterization of Pyrolysis Prooucts
Authors: Schwartz Kenneth B. , Rowcliffe David J. , Blum Yigal D. , Laine Richard M.
Published: March 2011

Characterization of the pyrolysis products of preceramic polysilazanes synthesized by reactions of the oligomer-[H2SiNMe]x in the presence of Ru3(CO)12catalyst has demonstrated that these polymers have great potential as precursors of Si3N4for several applications. The polysilazanes studied are viscous liquids that can be converted to ceramic material with a yield of >65 wt %. The vitreous product contains regions of fully dense material and large cavities that indicate of considerable gas evolution. A preliminary pyrolysis sequence has been constructed based on a combination of TGA of the polymer, SEM investigation of the product, and mass spectroscopic analysis of the gases and heavy fragments released during conversion of the polysilazanes to ceramic material. This understanding of pyrolysis mechanisms will aid in developing even more effective polymeric precursors to Si3N4and in optimizing pyrolysis procedures for a variety of useful appl ications.
Differences Between Gel-Derived Melts and Those Produced by Batch Melting
Authors: Cooper Alfred R.
Published: March 2011

Properties of a system at equilibrium depend on pressure, temperature and composition. Thus for a melt produced by the sol-gel (SG) process to be different from an identical composition melted from batch (MB), both cannot be at equilibrium. Non equilibrium melts can be associated with structural differences or homogeneity differences. The former have been suggested for SG melts while the latter is always possible in MB melts. Appropriate relaxation times are presented for structural and heterogeneity relaxation. From this it is concluded that structural differences will not persist unless the SG melt is metastable with respect to the equilibrium melt. A method for testing this unlikely premise is proposed.

Melts which are imperceptibly different from equilibrium may have non-equilibrium crystal embryo distributions that relax toward equilibrium with a time constant longer than that for structural relaxation. A difference in embryo and stable nuclei distribution will result in different crystallization kinetics.
Are Gel-Derived Glasses Different from Ordinary Glasses?
Authors: Weinberg M. C.
Published: March 2011

A review is presented of some of the previously reported differences and similarities between comparable gel glasses (and gels) and ordinary glasses. In this regard, considerations are made with respect to such factors as structure, physical and thermal properties, and phase transformation behavior. A variety of silicate lass compositions are used for illustrative purposes. The discussion is roughly ivided into two sections; low and high temperature behavior. At low temperatures one anticipates that differences between gel and conventional glasses will exist, but such dissimilarities are not expected to persist to high temperatures. However, experimental evidence is presented which indicates the perpetuation of such differences to very high temperatures. A partial resolution for this anomalous behavior is offered.
Electron-Spin Resonance and other Spectroscopies used in Characterizing Sol-Gel Processing
Authors: Klein L. C. , Kordas G.
Published: March 2011

The molecular structure of sol-gel processed silica can be studied using electron-spin resonance (ESR) spectroscopy. Spectra reveal changes in structure from sol to gel and from gel to glass. Gels prepared under various conditions contain intrinsic and extrinsic defects. Other spectroscopies that have been used to investigate gels are nuclear magnetic resonance (NMR), Raman, and visible.
The Need for Controlled Heterogeneous Nucleation in Ceramic Processing
Authors: Messing Gary L. , Mcardle James L. , Shelleman Richard A.
Published: March 2011

The principles underlying controlled heterogeneous nucleation are reviewed. The application of these principles for the preparation of ceramic powders with equiaxed morphology and narrow size distribution is illustrated with examples from the literature and our recent work on alumina. It is concluded that controlled heterogeneous nucleation will be an important factor in fully realizing the benefits of chemically derived polycrystalline ceramics.
Comparison of Clay-Water Systems With Aluminum Hydroxide Gels Prepared in Acidic Media
Authors: Pierre A. C. , Uhlmann D. R.
Published: March 2011

Alumina sols made by the hydrolysis of aluminum sec-butoxide in an acidic medium have been found to show behavior during drying and aging which appears similar to that reported for gels in a number of clay-water systems. Structural and phenomenological characteristics of these two classes of materials are compared. The extension to aluminum hydroxide systems of the models proposed to explain the gelation of clay sols are discussed, and a model is presented to describe the gelation behavior of aluminum hydroxide sols.
Molecular Dynamics Modeling of the Structural Failure of Glass
Authors: Simmons Joseph H. , Montrose Charles J.
Published: March 2011

Molecular Dynamics (MD) methods for modeling the structure and kinetic behavior of ceramics and glasses are reviewed and discussed while emphasizing the effect of various potential functions on the structure developed and the relevance of model calculations. Two dynamic experiments from the authors’ research are used as examples of modeling technique and interpretation of results. In the first, a Lennard-Jones force function is used to model the behavior of viscous liquids under large deformations. In the second, the brittle response of amorphous SiO2 modeled with an ionic Born-Mayer-Huggins interparticle potential is investigated at very high deformation rates. A comparison of results with experiment show the limitations and the great promise of the MD approach.
Ceramic Microstructure-Property Fractal-Diffractal Calculus : Static Synergetics Yield Optimization During Processing Via Real–Time Q.A.and Interactive Q.C
Authors: Siegel Edward
Published: March 2011

Ceramic microstructure-property relationships dominate any and all attempts at“better ceramics through chemistry”. Required is some universal calculus to allow analytic, universal, reversible scalable computation of one from the other. Static Synergetics universality-principle provides such a flexible versatile tool, heretofore not available. It is a reexpression of the very basic three laws of thermodynamics into r-,k-,and w-domainsthe equivalence of(symmetry-breaking/defect) Pattern-recognition(the “structure”) to signal-processing(the frequency-dependent FM) properties/ Functions. More basically, it is a manifestation of Noether's theoremthe basis of mechanics and orgin of the energy continuity equation that is the thermodynamic first law. Such an algorithm, the”software”of yield optimization(quality and quantity) real-time Q.A. and(in parallel with a specificity dominated process- model)interactive Q.C.requires as “hardware”produced input the small-angle-scattering(SAS)dominated diffraction-pattern/static structure factor SSAS(k) or Fourier transform r-domain Pattern/ photomicrograph-recognition imaging(of processing-introduced property-detrimental defects(heterogeneity heirarchy)). Output are universal FM:I/f flicker(voltage and/or current)noise power spectrum, signal-to-noise ratio over dynamic rangemulti-level system dominated anomalous low temperature/frequency thermalracoustic. properties, and 1/f relaxation response susceptibility polarization catastrophe derived dielectric, electrical, optical, noise, viscoelastic/mechanicalmagnetic,...property Functions. Input can be the ubiquitous,...universal Mandelbrot fractals,dominating ceramics;output(and internal)Functions are Berry-Nye-Jakeman wdomain diffractals,dominating all properties universally.How and Why it works are detailed exactly;universality, reversibility and scalability are analytically insured for self-similar(or selfaffine) fractal scaling-relation Pattern-recognition input;approximate. deviations from universal Functions output obtains from less than perfect mathematically ideal fractal scaling-relation Pattern-recognition input.Static Synergetics provides a new practical use for external radiation small-angle-scattering(SAS) diffraction-pattern/static structure factor measurements in ceramic material microstructure-property relationships during processing
Ceramics From Hydridopolysilazane
Authors: Legrow Gary E. , Lim Thomas F. , Lipowitz J. , Reaoch Ronald S.
Published: March 2011

The Advanced Ceramics Based on Polymer Processing Program is sponsored by the Defense Advanced Research Projects Agency (Materials Science Division). The objectives of the program include development of a family of Si-C, Si-N, and Si-C-N ceramic fibers which may be used for reinforcement in ceramic, metal and plastic matrices, and development of economical process technology for fabricating ceramic matrix composites with high fracture toughness, high temperature performance and no inherent limitations to forming complex shapes. Attainment of these objectives would circumvent two limitations of existing ceramic material technology - lack of design reliability due largely to catastrophic failure related to brittleness, and inability to fabricate complex shapes [1].
29Si NMR, Sec and Ftir Studies of The Hydrolysis and Condensation of Si(OC2H5 )4 and Si2O(OC2H5)6
Authors: Lin Chia-Cheng , Basil John D.
Published: March 2011

The hydrolysis and initial condensation reactions of Si(OC2H5)4 and low order polyethoxysiloxanes have been studied with high resolution 29Si NMR and size exclusion chromatography/FTIR spectroscopy. The effects of various parameters such as H2O/TEOS mole ratio, catalyst, pH, solvent, temperature and aging have been observed in the different nature of the reaction products. The products include partially hydrolyzed and unhydrolyzed Si(OC2H5)4, Si2O(CH2H5)6, and Si3O2(OC2H5)8. The rate of formation and concentration of each product obtained under different conditions provides information about the reactivity of various silanol-containing species and the factors that affect the overall reaction scheme.
Zirconia Characterization by Perturbed Angular Correlation Spectroscopy
Authors: Jaeger Herbert , Gardner John A. , Haygarth Ohn C. , Rasera Robert L.
Published: March 2011

Perturbed Angular Correlation spectroscopy of 181Ta nuclei occupying cation sites has been used to investigate microscopic structural properties of several pure and stabilized zirconia materials. The PAC spectra are used to derive the electric field gradients at the tracer nucleus. Thse are compared with calculations based on a simple point-ion model. Agreement between experiment and theory is good for stabilized material and qualitatively reasonable for pure zirconia.
EPR of Cu(II) in Sol-Gel Prepared SiO2 Glass
Authors: Dave S. , Maccrone R. K.
Published: March 2011

SiO2 glass has been prepared by the hydrolysis of TEOS in alcohol using HCl and NH4OH to control the pH. Copper ions were incorporated from the acetate to act as structural probe ions during the process of gellation and calcination. The local structure of copper ions was investigated using EPR determined at 300 K and 10 K.

It was found that the pH of the solution had a profound effect on the EPR spectra of the copper in the gels and glasses, indicating differences in the local structure.
Microporous Layers from Sol-Gel Techniques
Authors: Larbot A. , Alary J. A. , Fabre J. P. , Guizard C. , Cot L.
Published: March 2011

In separative process, the use of mineral membranes instead of organic ones is more interesting for it offers numerous advantages as follows :

- High temperature and pressure resistant (no compression of the membrane).

- Corrosion and abrasion resistant.

- Not sensitive to bacterial action.

- Steam sterilisable.

- Longer life time.
Effects of Hydrolysis On Metallo-Organic Solution Deposition of PZT FILMS
Authors: Lipeles Russell A. , Coleman Dianne J. , Leung Martin. S.
Published: March 2011

The effects of hydrolysis on the degree of polymerization during metallo-organic solution deposition of lead zirconate titanate (PZT) films have been investigated. The reaction of lead 2-ethylhexanoate, zirconium n-tetrapropoxide, and titanium tetrabutoxide in isopropanol with water were studied using thermogravimetry, specular reflectance Fourier transform infrared spectroscopy (FTIR) and optical and electron microscopy.

Films prepared from coating solutions having varying amounts of water exhibited dramatic differences in morphology. The films were spin-coated on platinum coated fused silica substrates and annealed at 525°C for 30 minutes. Unhydrolyzed coating solutions and solutions with a mole ratio of water to total metal of 0.5 yielded perovskite films with 0.5–5μm grains. A mole ratio of 1.5 (the amount of water required to completely hydrolyze the metallo–organics in the solution) formed amorphous, porous films. The stability of the prepolymerized films inhibits crystallization and densification at moderate temperatures.
Iron-Oxide and Yttrium-Iron-Oxide Thin Films a Test of the Feasibility of Producing and Measuring Micro- and Millimeter-Wave Materials
Authors: Bruce Ralph W. , Kordas George
Published: March 2011

Tin-oxide/iron-oxide and yttrium-iron-oxide thin-films have been produced with the sol-gel method. Film thicknesses from 50 to 155 nm were deposited by the sol-to-gel transformation onto borosilicate substrates. The dielectric losses of the films were deduced by the complex reflection coefficient of these materials in the range from 2 GHz to 18GHz using an HP network analyzer.

Samples of 5 cm × 5 cm were centered on the waveguide flange and a shorting plate (12.2 cm × 15.2 cm) of brass centered over the sample. Measurements were automatically made using the HP software provided.

In the X-Band region, three absorption bands at 8.3, 9.4, and 11.5 GHz were detected for the substrate, with losses (absorption peaks) ranging from 13.5, 11.9, and 9.9, respectively. For the tin-oxide/iron-oxide sol-gel coated substrate, three bands at 8.4, 9.5, and 11.6 GHz were observed having losses of 16.2 to 13.4, 12.9 to 11.4. and 11.3 to 9.7, respectively, depending upon thickness and orientation. For the yttrium-iron-oxide sol-gel coated substrate, three bands at 8.4, 9.5, and 11.6, with losses depending upon solgel thickness and orientation.
Siloxane Modified Sio2-TiO2 Glasses Via Sol-Gel
Authors: Parkhurst C. S. , Doyle W. F. , Silverman L. A. , Singh S. , Andersen M. P. , McClurg D. , Wnek G. E. , Uhlmann D. R.
Published: March 2011

Polydimethylsiloxane [PDMS]-modified SiO2-TiO2, glasses have been prepared via the sol-gel route. Polymer compositions varied between 17 and 67 wt% PDMS, using PDMS of molecular weights 1,700 and 36,000. Also varied was the Si/Ti ratio for a given polymer content and the nature of the Ti alkoxide.A general synthetic procedure was found which made optically clear samples. Dense monolithic structures were obtained at room temperature for all compositions. The room temperature densification is attributed to relaxation and flow in the sample due to the presence of the polymer. The effects on properties of the overall composition and molecular weight of the polymer are reported, and implications in terms of structural models are considered.
Oxide -Non-Oxide Composites By Sol-Gel
Authors: Pope Edward J. A. , Mackenzie J. D.
Published: March 2011

In this paper, three types of composites prepared using the sol-gel process are examined. Porous composites, based upon the dispersion of solid, oxide and non-oxide ceramic particles in a sol-gel derived matrix are described. A transparent composite, prepared by the impregnation of a polymer phase into a porous gel matrix is presented. Light-weight, “triphasic” composites, possessing good abrasion resistance and high fracture ductility, can also be fabricated by the polymer impregnation of a porous gel composite.
Raman Studies of Carrier Activation in Laser Annealed GaAs Capped with Silicon Nitride
Authors: Compaan A. , Abbi S. C. , Yao H. D. , Bhat A. , Hashmi F.
Published: March 2011

Carrier concentrations exceeding 1019/cm3 in GaAs implanted with Si (2 × 1014/cm2 @ 140 keV) have been obtained by pulsed laser annealing with either a dye laser (λ = 728 nm) or a XeCl excimer laser (λ = 308 nm). Carrier concentrations were measured by plasmon Raman scattering over a wide range of anneal energy densities. Compared with capless laser annealing, much higher carrier activations were achieved when the annealing laser pulse was incident through a Si3N4 cap.
Reactive Quenching at Liquid-Solid Interface Induced by Pulsed Ruby Laser Treatment: Aqueous Oxidation of Iron.
Authors: Ogale S. B. , Patil P. P. , Phase D. M. , Kulkarni S. A. , Ghaisas S. V. , Bhide V. G.
Published: March 2011

This paper demonstrates that metastable compounds can be synthesized on solid surface via pulsed laser induced processes at the liquid solid interface. Specifically, it is shown that the metastable oxides of iron can be obtained when an iron foil immersed in water is treated with Ruby Laser pulses [ λ =693.4 nm, pulse width 30 ns, energy density 10 J/cm2].The oxide has been characterized by using the techniques of conversion electron Mössbauer spectroscopy, X-ray diffraction and Rutherford Backscattering Spectrometry. The oxygen concentration near the surface as well as the depth scale over which it falls to zero can be varied by changing the laser treatment parameters such as pulse to pulse overlap, energy per pulse etc. A near-surface composition of ∼50 at.% and a depth scale of oxygen incorporation of a few thousand A° can be easily achieved. The phase transformation of a metastable oxide under thermal treatment is also explored. The mechanisms which could be responsible for the observed effects are commented upon. Some iron foils have been treated in air using comparable laser pulse parameters to obtain a comparision between treatment in air and liquid. Interestingly these foils show presence of √-Fe, which is a high temperature phase of iron known to be unstable at room temperature when pure. Other possible applications of laser processing of solids in liquid media are also discussed.
Pulsed Laser Induced Melt and Phase Transformation of Ni Silicide Layers on Si Substrate
Authors: Baeri P. , Grimaldi M. G. , Priolo F. , Rimini E. , Cullis A. G. , Chew N. C.
Published: March 2011

Thermally grown Ni2 Si and NiSi2 layers on <111> Si substrates were irradiated by 40 ns Nd laser pulses in the energy density range 0.3–2.0 J/cm2. The samples were analyzed by time-resolved reflectivity, 2.0 MeV He+ Rutherford backscattering in combination with channeling and by transmission electron microscopy. In the NiSi2/Si system the melt starts at the free surface (1280 K) and propagates towards the inside. Dissolution of substrate silicon atoms occurs when the silicon temperature reaches the liquidus temperature (1400 K). In the Ni2Si/Si samples the melt starts instead at the interface when it reaches the eutectic temperature (1250 K). The subsequent propagation towards the surface is limited by the mass transport of silicon atoms to maintain a composition near that of the eutectic. In some cases the surface may melt also at the congruent melting temperature (1570 K), giving rise after solidification to a quite complex structure. The different behaviour of the two silicides/silicon systems is explained in terms of phase diagram.
A Hydrodynamic Study of Laser-Induced Vaporization of Aluminum in Vacuum
Authors: Brost G. A. , Bohn C. L. , Crawford M. L. , Mullins B. W.
Published: March 2011

The three-dimensional hydrodynamics of laser-induced, steady state vaporization of aluminum (2024) in vacuim was investigated with the aid of both a hydrodynamic computer code and a Mach-Zender interferometer. Provided the laser beam is sufficiently intense, a vapor plasma forms, resulting in a sustained region of high pressure near the target. The pressure is distributed asymmetrically over the footprint in the case of oblique incidence.
Time-Resolved Crystallization of GeTe
Authors: Huber E. , Marinero E. E.
Published: March 2011

Amorphous thin films of GeTe were irradiated with excimer laser pulses and the subsequent crystallization was investigated utilizing simultaneous transient reflectivity and conductivity measurements. Below a threshold fluence of 15 mJ/cm2 pure thermal behaviour was found. Above that value, nucleation and growth are observed during the cooldown process. Above a fluence of 22 mJ/cm2 the films crystallize to a large degree within 200ns. Between 15 and 22 mJ/cm2 crystallite nuclei are formed (“frustrated crystallization”), and application of a subsequent pulse over areas exposed to this fluence regime leads to extremely fast crystallization (50 ns).
Analysis of Picosecond Pulsed Laser Melted Graphite
Authors: Steinbeck J. , Braunstein G. , Speck J. , Dresselhaus M. S. , Huang C. Y. , Malvezzi A. M. , Bloembergen N.
Published: March 2011

A Raman microprobe and TEM have been used to analyze the resolidified region of liquid carbon generated by picosecond pulse laser radiation. From the relative intensities of the zone center Raman-allowed mode for graphite at 1582cm−1 and the disorder-induced mode at 1360cm−1 , the average graphite crystallite size in the resolidified region is determined as a function of incident pulse energy density. By comparing with Rutherford backscattering spectra and Raman spectra from nanosecond pulsed laser melting experiments, additional information about the disorder depth in picosecond pulsed laser melted graphite is obtained. Comparisons of TEM micrographs for nanosecond and picosecond pulsed laser melting experiments show that the structure of the laser disordered regions in graphite are similar and exhibit similar behavior with increasing laser pulse fluence. The similarities in the resolidified regions under both irradiation schemes discourages a determination of the properties of liquid carbon after the liquid has resolidified.