bluuebunny/crossref_metadata_2025 huggingface dataset:
X-Ray Diffraction and Reflectivity Studies of Thin Porous Silicon Layers
Authors: Buttard D. , Dolino G. , Bellet D. , Baumbach T.
Published: April 2011

High resolution X-ray diffraction and reflectivity have been used for the structural characterization of thin porous silicon layers of p and p+ doping type. Thin porous silicon layers studied either by diffraction or reflectivity, in the range of 10–1000 nm, exhibit several thickness fringes, corresponding to a lateral homogeneity of the layer thickness. The comparison between the experimental results with simulations enables one to deduce structural information relative to the porosity, thickness, lattice parameter as well as interface thickness. For p+ type samples a double fringe system was observed, showing the existence of a surface film probably at the porous silicon layer top surface.
Optical Properties of Free-Standing Ultrahigh Porosity Silicon Films Prepared by Supercritical Drying
Authors: Von Behren J. , Fauchet P. M. , Chimowitz E. H. , Lira C. T.
Published: April 2011

Highly luminescent free-standing porous silicon thin films of excellent optical quality have been manufactured by using electrochemical etching and lift-off steps combined with supercritical drying. One to 50 μm thick free-standing layers made from highly (p+) and moderately (p) Boron doped single crystal silicon (c-Si) substrates have been produced with porosities (P) up to 95 %. The Fabry-Pérot fringes observed in the transmission and photoluminescence (PL) spectra are used to determine the refractive index. At the highest P the index of refraction is below 1.2 from the IR to 2 eV. The absorption coefficients follow a nearly exponential behavior in the energy range from 1.2 eV and 4 eV. The porosity corrected absorption spectra of free-standing films made from p type c-Si substrates are blue shifted with respect to those prepared from p+ substrates. For P > 70 % a blue shift is also observed in PL. At equal porosities the luminescence intensities of porous silicon films made from p+ and p type c-Si are different by one order of magnitude.
Selection Rules in the Raman Spectrum of Porous Silicon
Authors: Agulló-Rueda F. , Moreno J. D. , Montoya E. , Guerrero-Lemus R. , Martín-Palma R. J. , Martínez-Duart J. M.
Published: April 2011

We have measured the Raman spectrum of porous silicon layers for different light polarizations. For the polarizations where the first-order Raman peak is forbidden in bulk silicon, porous silicon shows a band. This band is almost as intense as the one in the allowed polarizations but its lineshape is very different. The ‘forbidden’ band is usually wider and shifted to lower energies with respect to the allowed band. Both bands are analyzed in terms of sample characteristics, layer depth, and excitation wavelength.
Transient Photocurrent Response of Dye-Sensitized Porous Nanocrys1Alline TiO2 Electrodes
Authors: Goossens Albert , Boschloo G. K. , Schoonman J.
Published: April 2011

In order to investigate the fundamentals of electron migration in nanostructured metal-oxide semiconductors, the transient photocurrent response of dye-sensitized porous nanocrystalline TiO2 is studied. The time-resolved photocurrent response at light steps or pulses shows a faster transient upon increasing the light intensity. Intensity-modulated photocurrent spectroscopy (IMPS) reveals that the transient photocurrent is dominated by two time constants, i.e. the geometrical one and a characteristic time related to electron trapping. A theoretical model is derived in which the occupation dynamics of a single electron trap is considered using Shockley-Read-Hall kinetics. The geometrical RC time of the electrode is also included. Excellent agreement between this model and the measured IMPS spectra is obtained.
Visible Light Emitting Diode Employing Electrochemically Anodized Nanocrystalline Silicon Thin Film
Authors: Toyama T. , Yamamoto T. , Matsui T. , Okamoto H.
Published: April 2011

Visible electroluminescence (EL) has been achieved on the entirely solid state thin film light emitting diode (TFLED) employing electrochemically anodized nanocrystalline Si (nc-Si) as a light emitting active layer. The TFLED consisting of p-type nc-Si, and intrinsic and n-type amorphous layers was fabricated on a SnO2-coated glass substrate. The nc-Si was formed in HF aqueous solution from boron doped microcrystalline Si (μc-Si) deposited by rf plasma chemical vapor deposition (CVD). The TFLED exhibits clear rectification with a forward threshold voltage of about 1.5 V, whereas visible EL emission is observed upon applying reverse bias voltages. The diode ideality factor is more than 2, and the light output increases with the square of the diode current. The EL emission color is orange-red and the spectral peak energy is 1.8 eV.
Electroluminescence and Carrier Transport in Leds Based on Silicon-RICH Silicon Oxide
Authors: Tsybeskov L. , Hirschman K. D. , Duttagupta S. P. , Fauchet P. M.
Published: April 2011

LEDs based on silicon-rich silicon oxide (SRSO) have been fabricated utilizing thermal oxidation of electrochemically etched c-Si and standard microelectronic processes including LPCVD, photolithography, ion implantation and metallization. The bipolar devices consist of heavily-doped polycrystalline Si, a transition layer made of oxidized mesoporous Si, an active SRSO layer (doped or intrinsic) and a crystalline Si substrate. The LED's electrical properties exhibit a low interface state density which is explained by the partial filling of the micropores within the transition layer by polycrystalline Si. The dominant carrier transport in SRSO is due to thermally-assisted tunneling at low fields and electric field-assisted (Fowler-Nordheim) tunneling at high fields. The electroluminescence (EL) is stable and the EL modulation is limited by the carrier transition time (not by the carrier lifetime) which explains the high modulation speed (≥ 10 MHz). We have fabricated a prototype alphanumeric 7-segment display with an isolated version of the LEDs and standard microelectronic processing techniques.
A Study of the Factors Which Determine the Modulation Speed of a Shallow PN Junction Porous Silicon Led
Authors: Simons A. J. , Cox T. I. , Loni A. , Calcott P. D. J. , Uren M. J. , Canham L. T.
Published: April 2011

The effect of the chemical thinning of the porous silicon structure on the speed and efficiency of electroluminescent devices, produced by the anodisation of a pn junction in bulk silicon is investigated. Thinning of the silicon wires results in an increase in the efficiency but at the expense of a reduction in operating speed. It is demonstrated that the operating speed is limited by the photoluminescence lifetime for small signal excitation. However, for large signals, the electroluminescence can be turned off more than 5 times faster than the photoluminescence lifetime, indicating that this need not necessarily limit device operating speed.
Grain-Size Control of Nanocrystalline Silicon by Pulsed Gas Plasma Process
Authors: Itoh A. , Ifuku T. , Otobe M. , Oda S.
Published: April 2011

A new method for the formation of nanocrystalline Si (nc-Si) in the SiH4 plasma using pulsed-H2 supply with very-high-frequency (VHF;144MHz) excitation is proposed to control the size of nc-Si. Nanocrystalline Si is formed in the gas phase of SiH4 plasma cell by coalescence of radicals. The principle of size control is based on the separation of nucleation and growth process. Supplying H2 into a SiH4 plasma enhances nucleation of nc-Si and suppresses growth rate of nc-Si. The nucleated nc-Si grows larger in a SiH4 plasma during the off state of the H2 supply. As the newly supplied H2 forces nc-Si grown in the previous cycle out of the plasma cell into the deposition chamber, the next nucleation of nc-Si is enhanced simultaneously. Using this method, we fabricated 8 nm-diameter nc-Si with small dispersion (±1 nm) successfully.
Synthesis, Optical Properties, and Microstructure of Semiconductor Nanocrystals Formed by Ion Implantation
Authors: Budai J. D. , White C. W. , Withrow S. P. , Zuhr R. A. , Zhu J. G.
Published: April 2011

High-dose ion implantation, followed by annealing, has been shown to provide a versatile technique for creating semiconductor nanocrystals encapsulated in the surface region of a substrate material. We have successfully formed nanocrystalline precipitates from groups IV (Si, Ge, SiGe), III-V (GaAs, InAs, GaP, InP, GaN), and II-VI (CdS, CdSe, CdSxSe1x, CdTe, ZnS, ZnSe) in fused silica, Al2O3 and Si substrates. Representative examples will be presented in order to illustrate the synthesis, microstructure, and optical properties of the nanostructured composite systems. The optical spectra reveal blue-shifts in good agreement with theoretical estimates of size-dependent quantum-confinement energies of electrons and holes. When formed in crystalline substrates, the nanocrystal lattice structure and orientation can be reproducibly controlled by adjusting the implantation conditions.
Fabrication of Polycrystalline Si Thin Film for Solar Cells
Authors: Tanaka M. , Tsuge S. , Kiyama S. , Tsuda S. , Nakano S.
Published: April 2011

The a-Si/poly-Si thin film tandem solar cell is a promising candidate for low-cost solar cells. We have conducted R&D on poly-Si thin film using the Solid Phase Crystallization (SPC) method from amorphous silicon (a-Si). To improve the film quality of SPC poly-Si, we have developed a new SPC method called the partial doping method. This method features two stacked starting a-Si layers, a P-doped layer and a non-doped layer. Nucleation occurs in the P-doped layer, and the non-doped layer is the crystal growth layer. For the nucleation layer, we developed a Si film with a unique structure, which features relatively large crystallites (-1000A) embedded in a matrix of amorphous tissue. By combining these technologies, a conversion efficiency of 9.2% was obtained for poly-Si thin-film solar cells. For further improvement in the conversion efficiency, based on the concept of “independent control of nucleation and crystal growth”, it is necessary to combine the best fabrication methods for each layer. A high conversion efficiency of more than 12% was found possible by using the CVD method and a new back surface reflection structure.
Visible Photoluminescence From Si Ion-Implanted and Thermally Annealed SiO2 Films
Authors: Kanemitsu Y. , Shimizu N. , Okamoto S. , Komoda T. , Hemment P. L. F. , Sealy B. J.
Published: April 2011

We have experimentally studied the photoluminescence (PL) properties of Si clusters in SiO2 glassy matrices. Si clusters in the SiO2 matrices were fabricated by Si+ ion implantation into SiO2 glasses and then thermally annealed in forming gas. Broad PL peaks are observed in the visible spectral region at room temperature. Resonantly excited PL spectra indicate that the strong coupling of excitons and stretching vibrations of the Si-0 bonds causes the broad luminescent spectra. It is concluded that the interaction between electronic and vibrational excitations controls the luminescent emission and the observed dynamics.
Properties of Nanophase Materials Synthesized by Mechanical Attrition
Authors: Fecht H.-J. , Moelle C.
Published: April 2011

Mechanical attrition and mechanical alloying has been developed as a versatile alternative to other processing routes in preparing nanophase materials with a broad range of chemical composition and atomic structure. In this process, lattice defects are produced by “pumping” energy into initially single-crystalline powder particles of typically 50 μm particle diameter. This internal refining process with a reduction of the average grain size by a factor of 103– 104results from the creation and self-organization of small-angle and high-angle grain boundaries within the powder particles during the milling process. This microstructural evolution has been characterized by X-ray, neutron and electron scattering methods revealing the grain refinement and increase in internal stress. As a consequence, a change of the thermodynamic, mechanical and chemical properties of these materials has been observed with the properties of nanophase materials becoming controlled by the grain size distribution and the specific atomic structure and cohesive energy of the grain or interphase boundaries. An analysis of the thermal stability of attrited powder specimen gives the grain boundary energy of non-equilibrium and fully relaxed grain boundaries as well as their mobility. In summary, it is expected that the study of mechanical attrition processes in the future not only opens new processing routes for a variety of advanced nanophase materials but also improves the understanding of technologically relevant deformation processes, e.g. surface wear, on a nanoscopic level.
Preparation of Nanometer Sized Aluminum Powders
Authors: Johnson Curtis E. , Higa Kelvin T.
Published: April 2011

Nanometer aluminum powders have been prepared from the catalytic thermal decomposition of aluminum hydride adducts in organic solvents. This process provides excellent control of particle size and uniformity with batch particle sizes ranging from 50 to 600 nm. Variables affecting particle size were explored, including reaction temperature, catalyst concentration, and adducting amine concentration. Passivation techniques of the reactive aluminum powders were established for safe handling in air. Samples were mainly characterized by scanning electron microscopy and thermogravimetric analysis.
Three-Dimensional Superlattice Packing of Faceted Silver Nanocrystals
Authors: Harfenist S. A. , Wang Z. L. , Alvarez M. M. , Vezmar I. , Whetten R. L.
Published: April 2011

Orientational ordering of faceted nanocrystals in nanocrystal arrays has been directly observed for the first time, by use of transmission electron microscopy imaging and diffraction to resolve the structure of thin molecular-crystalline films of silver nanocrystals passivated by alkylthiolate self-assembled monolayers. The type of ordering found is determined by the nanocrystals faceted morphology, as mediated by the interactions of surfactant groups tethered to the facets on neighboring nanocrystals. Orientational ordering is crucial for the understanding of the fundamental properties of quantum-dot arrays, as well as for their optimal utilization in optical and electronic applications.
Preparation of Metal Nanosuspensions by High-Pressure DC-Sputtering on Running Liquids
Authors: Wagener M. , Murty B. S. , Günther B.
Published: April 2011

A modified VERL-process (Vacuum evaporation on running liquids) employing high pressure magnetron sputtering has been used for the preparation of suspensions with metal nanoparticles. The method has been tested for Ag- and Fe-suspensions by varying the pressure of the Argon sputtering atmosphere in the range of 1 to 30 Pa. A narrow particle size distribution with a mean particle size ranging from 5–18 nm has been found. The mean particle size increases with increasing Argon pressure in the pressure range under investigation. A descriptive model for the process of particle formation as a function of sputtering gas pressure is given.
Characterization of Consolidated Rapidly Solidified Cu-Nb Ribbons
Authors: Ebrahimi F. , Henne M. L. C.
Published: April 2011

Copper-niobium ribbons produced by melt-spinning were compacted by swaging and consolidated using HIPping. Final processing to obtain in-situ composites was done by swaging. The strength of the composite is discussed in terms of the composition and morphology of the niobium phase as evaluated using electron microscopy techniques.
Commercialization Status of Ni3Al-Based Alloys
Authors: Sikka V. K.
Published: April 2011

The Ni3Al-based alloys have been under development at the Oak Ridge National Laboratory (ORNL) and other research institutions in the United States and around the world for the last ten years. The incremental developments of composition, melting process, casting methods, property data, corrosion data, weldability development, and prototype component testing under production-like operating conditions have pushed the ORNL-developed Ni3Al-based alloys closer to commercialization. This paper will present the highlights of incremental technical developments along with the approach and current status of commercialization. It is concluded that cast components are the primary applications of Ni3Al-based alloys, and applications range from heat-treating fixtures to forging dies. It is also concluded that the commercialization process is accelerated when technology is licensed to an organization that can produce the alloy, has component manufacturing capability, and is also a user.
TEM Characterization of Planar Defects in A Massively Transformed TiAl Alloy
Authors: Zhang X. D. , Wiezorek J. M. K. , Kaufman M. J. , Loretto M. H. , Fraser H. L.
Published: April 2011

The microstructure of a massively transformed Ti-49at.%Al alloy has been studied by conventional transmission electron microscopy (CTEM) and high resolution TEM (HREM). A high density of planar defects, namely complex anti-phase domain boundaries (CAPDB) and thermal micro-twins (TMT) have been observed. CTEM images and diffraction patterns showed that two anti-phase related γ-matrix domains were generally separated by a thin layer of a 90°-domain, for which the c-axis is rotated 90° over a common cube axis with respect to those of the γ-matrix domains. HREM confirmed the presence of two crystallographically different types of 90°-do-mains being associated with the CAPDB. Furthermore, interactions between the CAPDB and TMT have been observed. Local faceting of the generally wavy, non-crystallographic CAPDB parallel to the {111}-twinning planes occurred due to interaction with the TMT. The relaxation of the CAPDB onto {111} required diffusion which is proposed to be enhanced locally in the presence of the dislocations associated with the formation of TMT during the massive transformation.
The Effect of Heat Treatment on the Microstructure and Properties of FeAl+Cr
Authors: Munroe P. R. , Kong C. H.
Published: April 2011

Microstructural studies were performed on an alloy of composition Fe45Cr5Al50 heat treated at 950°C and oil-quenched and then given isothermal annealing treatments for times up to 200 hours at either 400°C or 500°C. The observed microstructures were correlated with variations in hardness during isothermal annealing. It was deduced that the thermal vacancies retained following the initial heat treatment are removed relatively rapidly from the lattice, which leads to an initial drop in hardness. However, during prolonged annealing, the coarsening of bothFeAl2 particles and a disordered a(Fe,Cr) phase leads to further softening. It was also deduced that the chromium atoms, which remain in solution, are effective solute strengtheners. The a(Fe,Cr) phase, which is coherent with the B2 matrix, appears to coarsen by a ledge growth mechanism.
A Model for the Yield Strength Anomaly in FeAl
Authors: Baker I. , George E. P.
Published: April 2011

A phenomenological model is used to explain the yield strength anomaly in FeAl. The model incorporates hardening by thermal vacancies at intermediate temperatures, and dislocation creep at elevated temperatures. Since the vacancy concentration increases exponentially with increasing temperature, the model predicts an exponential increase in strength with increasing temperature. This increasing strength is terminated by the onset of dislocation creep. The model captures the experimentally-observed strain rate dependency of the yield stress at high temperatures, and yields an activation enthalpy for vacancy formation which is in excellent agreement with a previously measured value [1].
Examination of Dislocation Structures Near Crack TIP Region of B2 NiAl Alloys
Authors: Ng B-C. , Simkin B. , Crimp M. A.
Published: April 2011

The structure and distribution of dislocations in the region of crack tips and crack edges have been examined in single crystal stoichiometric B2 NiAl using electron channeling contrast imaging (ECCI). ECCI, which allows examination of near surface substructural crystalline defects in bulk specimens, has been carried out for undeformed as well as in-situ deformed 4-point bend specimens. Images of dislocations at crack tips and along the crack fracture surfaces have been studied. Observations have been correlated with variations in thermal treatment corresponding with brittle and toughened conditions. A higher dislocation density was observed over a larger region in front of crack tips for the toughened materials as compared to brittle material.
Practical Design of Ni3Al with High Hot Workability
Authors: Wang Yinmin , Lin Dongliang , Zhang Yun
Published: April 2011

From our previous work, Ni3Al polycrystals with combined addition of magnesium and silicon kept high values of compressive strain at rupture (CSR) when the strain rate rose. In order to further improve hot workability of Ni3Al, 7.9wt.% Cr was added. The compressive tests showed that 30%∼40% CSR values of the alloy had been kept in a wide temperature range of 1173K-1373K at strain rates of 10-2sec-1 and 10-2sec-1 in contrast with 15%∼25% CSR values of the alloy without Cr addition.

In practical hot rolling process, at initial deformation temperature of 1373K, strain rate of 1.0 sec-1 and by controlling reduction within 10∼15% each rolling pass, Ni3Al ingots were successfully hot-rolled into polycrystals with different deformations, the maximum of which was 55%. The deformed alloys had manifestly enhanced mechanical properties shown by tensile tests.

The dislocation configurations of deformed alloys have been investigated by using transmission electron microscope(TEM).
Plastic Deformation of Mo(Si,Al)2 Single Crystals with the C40 Structure
Authors: Moriwaki M. , Ito K. , Inui H. , Yamaguchi M.
Published: April 2011

The deformation behavior of single crystals of Mo(Si,Al)2 with the C40 structure has been studied as a function of crystal orientation and Al content in the temperature range from room temperature to 1500°C in compression. Plastic flow is possible only above 1100°C for orientations where slip along <1120> on (0001) is operative and no other slip systems are observed over whole temperature range investigated. The critical resolved shear stress for basal slip decreases rapidly with increasing temperature and the Schmid law is valid. Basal slip appears to occur through a synchroshear mechanism, in which a-dislocations (b=1/3<1120>) dissociate into two synchro-partial dislocations with the identical Burgers vector(b*1/6<1120>) and each synchro-partial further dissociates into two partials on two adjacent planes.
Preparation, Structure and Mechanical Properties of RuAl and (Ru,Ni)Al Alloys
Authors: Sabariz A. L. R. , Taylor G.
Published: April 2011

The intermetallic compound, RuAl with B2 CsCl type structure, has been shown to possess room-temperature toughness and plasticity. NiAl also forms a B2 compound and it is claimed that a pseudo-binary compound, (Ru,Ni)Al, may be formed because the difference in lattice parameter between the two binary phases is slight. In this work a study has been made of the mechanical properties of some polycrystalline compounds, across the RuAl-(Ru,Ni)Al pseudo-binary, prepared from high-purity elemental powders. Compressive yield stresses were measured between room-temperature and 900°C, and the mechanisms of plastic flow are discussed in relation to the dislocation structures observed by TEM. Hot-microhardness tests were made to provide an indication of the effect of solid-solution hardening.
The Effect of Aluminum on the Formation of Orthorhombic Plates in the Nb-Ti-Al Ternary System
Authors: Hoelzer D. T. , Ebrahimi F.
Published: April 2011

Transmission electron microscopy (TEM) was used to study the phase transformation in an alloy containing 33Ti-27Nb-40Al (at.%). The results showed that the BCC β phase was present at high temperatures, which ordered to the B2 phase, and finally was martensitically transformed to a plate microstructure during quenching. The plates possessed an orthorhombic crystal structure and a substructure that consisted of both coarse and fine anti-phase domain boundaries (APDBs). These APDBs were consistent with three sublattices that were derived from the inherited site occupancy of the B2 matrix and a subsequent disorder to order transition. The CBED analysis of the plates showed that the site occupancy of this orthorhombic phase was consistent with the Al2NbTi stoichiometry with Al occupying the 8g, Nb the 4c1, and Ti the 4c2 Wyckoff sites.
Development Of Miscible Blends From Intrapolymer Repulsive Interactions: Polycarbonate/Polystyrene Ionomers
Authors: Xie R. , Weiss R. A.
Published: April 2011

The phase behavior of blends of zinc sulfonated polystyrene (ZnSPS) and bisphenol-A polycarbonate (PC) was studied as a function of the sulfonation level and the molecular weight of the ZnSPS ionomer. The system exhibits upper critical solution temperature (UCST) behavior. The cloud point temperatures increased with increasing ZnSPS molecular weight and decreased with increasing sulfonation level. No strong interactions between ZnSPS and PC were detected by FTIR. The composition dependence of the glass transition temperatures of the miscible blends exhibited negative deviation from linear additi vity, which is consistent with no or weak interactions between ZnSPS and PC. Miscibility is believed to arise from strong repulsive interactions between the charged and uncharged species on the ionomer chain.
Thermal Characterization of a Microlayered Polycarbonate/Polymethyl Methacrylate Composite
Authors: Hsieh Alex J. , Gutierrez Alex W.
Published: April 2011

Thermal behavior of a coextruded microlayer composite with 388 alternating layers of polycarbonate and polymethyl methacrylate (PMMA) was investigated using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Two distinct glass transition temperatures were observed with DSC for the coextruded composite, however both were shifted very slightly towards each other, compared to the glass transition temperatures of the pure components, indicating limited miscibility. Adhesion between the alternating microlayers appeared to be very good; delamination did not occur after the microlayer composite was subjected to a high speed impact test. Adhesion is attributed to limited miscibility since little mixing resulted from the laminar flow which was required in the coextrusion process. DMA results revealed an additional damping peak, which was not observed with DSC, at a temperature between the glass transitions of the two components. This intermediate transition peak is more sensitive to change in frequency compared to the response for the individual pure components.
Microchemical Studies of Tuyeres and Refractory Materials used by Phoenicians and Punics at Tharros (Sardinia, Italy)
Authors: Ingo G.M. , Acquaro E. , Manfred L-I. , Bultrini G. , Chiozzini G. , Veroli C.
Published: April 2011

A large amount of smelting slags, tuyeres and curved refractory materials used during pyrometallurgical activities have been found at Tharros (western-Sardinia, Italy) during an excavation stratigraphically related to the Phoenician-Punic period (VI-IV BC). The microchemical structure of the vitrified end of tuyeres and of the thick fragments of the smelting furnaces, has been studied by means of scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDS). The results indicate that these materials can be associated with an iron smelting process. Furthermore, the temperature and duration of the smelting process has been estimated from the study of vitrification process and penetration depth of vitrification of the tips of some tuyeres combined with the study of pieces of clay taken from a unverified fragment of a tuyere and subjected to different thermal treatments under reducing atmosphere.
Incipient Maya Burnt-Lime Technology: Characterization and Chronological Variations in Preclassic Plaster, Stucco and Mortar at Nakbe, Guatemala
Authors: Hansen Eric F. , Rodriguez-Navarro Carlos , Hansen Richard D.
Published: April 2011

Patterned technological behaviors in the production and use of burnt-lime products can be characterized using optical microscopy and image analysis of pétrographie thin-sections to determine the texture (supplemented by X-ray diffraction analysis). Variations in technological styles have been identified in 21 samples from the ancient Maya site of Nakbe, Petén, Guatemala dating to the Middle Preclassic (1,000 B. C. - 300 B. C.) and Late Preclassic (300 B. C. - 150 A. D.) periods. Middle Preclassic floors exhibit a chaotic texture with a highly random aggregate particle size. Late Preclassic modeled stucco or painted fragments have a well-sorted texture with a low acid-insoluble content (<2%). Load -bearing mortar dating from the early Late Preclassic has a matrix with a high acid insoluble content (>15%), the major phases being quartz (-10%) and clays (∼5%). The variations correlate both with the time of occurrence and the function of the end-product. These issues of construction methods and levels of technology contribute data to aid our understanding of cultural development in this area at a critical time when the Maya were formulating power structures.
On-Site Non-Destructive MID-IR Spectroscopy of Plastics in Museum Objects Using a Portable Ftir Spectrometer with Fiber Optic Probe
Authors: Scott Williams R.
Published: April 2011

The easy determination of the chemical composition of the plastic components of museum objects has been identified as a critical requirement for the proper preservation and treatment of museum objects with plastic components. To date, chemical identification has been done by wet chemical spot tests applied directly on the object, or by spot tests or instrumental techniques such as IR spectroscopy on samples excised from objects. These methods are not satisfactory. Spot tests are neither comprehensive nor unambiguous, and instrumental techniques are not convenient since the instruments are generally located in analytical laboratories remote from the museum collections. This paper describes the use of a portable FTIR spectrometer with a fiber optic sampling probe to acquire mid-IR reflectance spectra from plastics in museum objects. The technique is non-destructive and is performed on-site at the museum collection. Results will be described with an emphasis on the practicalities of transporting the spectrometer and accessories, and collecting and interpreting spectra.
Principal Component Analysis of Spectral Data: A Contribution to the Knowledge of the Materials Constituting Works of Art
Authors: Bacci M. , Baronti S. , Casini A. , Lotti F. , Picollo M. , Porcinai S.
Published: April 2011

The use of totally non-destructive techniques such as image spectroscopy for diagnosing paintings makes it possible to obtain a large amount of spectral data that provides information concerning the composition of works of art. Here, we stress how statistical treatments, such as principal component analysis (PCA), applied to 2-D data, can contribute to a better knowledge of the work of art itself and of the distribution of the materials that constitute it.

Laboratory tests, as well as applications to actual paintings, will be presented and discussed.
The Evolution Process of the Ancient Chinese Yaozhou Porcelain
Authors: Leung P. L. , Hongjie Luo , Jiazhi Li , Stokes Michael J.
Published: April 2011

The chemical composition (body and glaze) of over thirty Yaozhou porcelain fragments are determined by X-ray fluorescence (XRF) analysis. Statistical analysis of these results combined with data already published indicate that the full evolution process of Yaozhou porcelain can be divided into four stages. Each stage exhibits a characteristic composition determined by the raw materials and batch composition used to produce the porcelain bodies and glazes. Almost all of Yaozhou celadon and white ware glazes belong predominantly to the CaO-type glaze (or lime glaze), but the glazes of the Song Dynasty (A.D. 960–1280) and later periods have higher K2O content and less CaO than the earlier periods.
AB Initio Pseudopotential Calculations of Dopant Diffusion in SI
Authors: Zhu Jing
Published: April 2011

The ab initio pseudopotential method is used to study transient-enhanced-diffusion (TED) related processes. The electronic degrees of freedom are included explicitly, together with the fully self-consistent treatment of the electron charge density. A large supercell and a fine k-point mesh are used to ensure numerical convergence. Such method has been demonstrated to give quantitative description of defect energetics. We will show that boron diffusion is significantly enhanced in the presence of the Si interstitial due to the substantial lowering of the migrational barrier through a kick-out mechanism. The resulting mobile boron can also be trapped by another substitutional boron, forming an immobile and electrically inactive two-boron pair. Similarly, carbon diffusion is also enhanced significantly due to the pairing with Si interstitiels. However, carbon binds to Si interstitials much more strongly than boron does, taking away most Si interstitials from boron at sufficiently large carbon concentration, which causes the suppression of the boron TED. We will also show that Fermi level effect plays an important role in both Si intersititial and boron diffusion.
Atomistic Model of Transient Enhanced Diffusion and Clustering of Boron In Silicon
Authors: Pelaz L. , Gilmer G. H. , Jaraiz M. , Gossmann H.-J. , Rafferty C. S. , Eaglesham D. J. , Poate J. M.
Published: April 2011

An atomistic model for B implantation, diffusion and clustering is presented. The model embodies the usual mechanism of Si self-interstitial diffusion and B kick-out and also includes the formation of immobile precursors of B clusters prior to the onset of transient enhanced diffusion. These immobile complexes, such as BI2 (a B atom with two Si self-interstitials) form during implantation or in the very early stages of annealing, when the Si interstitial concentration is very high. They then act as nucleation centers for the formation of B-rich clusters during annealing. This model explains and predicts the behavior of B under a wide variety of implantation and annealing conditions.
Defect Reduction and Improved Device Performance using Rapid Isothermal Diffusion in Silicon
Authors: Vedula L. , Singh R. , Ratakonda D. , Rohatgi A. , Narayanan S.
Published: April 2011

Quantum photoeffects associated with photons of wavelength less than 0.8 micron lead to higher bulk and surface diffusion coefficients. We have exploited this fundamental property in designing rapid isothermal processing (RIP) systems for shallow junction formation in silicon. A detailed comparative study of diffusion, metallization and CVD with and without high energy photons has been carried out. The results show that microscopic defects, cycle time and processing temperature is lower than what can be achieved byconventional methods is realized by using photons in the ultra violet (UV) and vacuum ultra violet (VUV) spectrum.
Diffusion and Self-Gettering of Nickel in Float Zone Silicon Wafers
Authors: Gay N. , Martinuzzi S.
Published: April 2011

External gettering techniques trap removed impurities in regions of a semiconductor which contain defects or in which the solubility is enhanced like in phosphorus diffused layers or in Al-Si alloy. If a fast diffuser like nickel is used in place of Al to obtain an alloy or a compound close to the surface, contamination and decontamination can occur resulting of the indiffusion and removal of nickel atoms. P type FZ samples were partly covered by nickel (nickel òn part 1 and not on part 2) and then annealed at 950°C for 1h.

As expected, after nickel indiffusion the diffusion length of minority carriers decreases but the values are always higher in part 1 than in part 2. Scanning infrared microscopy detects precipitates in part 2 and not in part 1. The results are explained assuming that the nickel-silicon compound formed at the surface serves as a diffusion source as well as an external self-gettering region.
Oxygen Stabilization of Damage Induced by Mev Ion Implantation
Authors: Jain Amitabh , Mercer Doug
Published: April 2011

As devices are scaled down and their performance is enhanced, the role of oxygen in silicon remains critical. The precipitation of oxygen away from the device region leads to desirable gettering of deleterious impurities and is a useful technique. In the device region, however, oxygen has recently been shown to take part in the annealing of dopant implants and segregate to damaged regions. This may result in the stabilization of damage structures and the attraction of unwanted impurities to sensitive regions of the device. In this work we examine these phenomena and their potential impact on device performance. For example, oxygen has been observed to segregate at two positions following a 1000°C, one hour anneal of a 2 MeV, 3.5×1015/cm2phosphorus implant into CZ p-Si. The oxygen concentration is greatly enhanced above its initial level of 1018O/cm3, both in the end-of-range region and at approximately half that depth, near the peak of the predicted damage profile. Iron deliberately introduced at the surface prior to annealing, getters out strongly at these locations No significant redistribution of carbon can be detected. The results assume significance in view of the increasing use of high energy implantation for both epi-layer replacement and retrograde well formation.
Microstructure of c-BN Films Deposited by IBAD: IR and Hrem Analyses
Authors: Ilias S. , Pascallon J. , Stambouli V. , Bouchier D. , Nouet G.
Published: April 2011

The in-depth distribution of phases in c-BN films deposited by Ion Beam Assisted Deposition (IBAD) at two different ion energy values (300 and 600 eV) was investigated using the quantitative IR transmission measurements and the HREM technique. Whatever the value of the studied ion energies, the characteristic layered morphology of c-BN film is observed including the interfacial sp2 zone between the substrate and the c-BN volume. In the case of 600 eV ion energy, this interfacial zone is less well-defined in comparison with 300 eV ion energy and the corresponding thickness is more important. Furthermore, the h-BN phase is more diluted within the c-BN film volume showing that the purest phase concentration of c-BN is found for the lowest ion energy, i.e. 300 eV.
The Spreading of a Void on a Facet During Electromigration
Authors: Chu X. , Bauer T C. L. , Mullinst T W. W. , Klinger L. M.
Published: April 2011

A void of cross sectional area A may spread perpendicular to the applied electric field Ea during electromigration because its leading surface develops a facet whose advance is limited by the supply of steps. If the facet is immobile (no step source) and the remaining surface is free to move, and if EaA is less than a threshold value, then the void assumes a stationary elongated shape dictated by a balance between capillarity and electric field. If EaA exceeds the threshold value, however, a balance is no longer possible, and the void spreads along the facet without arrest. If the facet has limited mobility, a balance is possible for all values of EaA, resulting in an elongated moving steady-state shape. The treatment simplifies the void shape as rectangular but preserves the essential features of capillarity and surface electromigration. We argue that the motion of a facet on a void along the outward normal requires defects (e.g. intersecting screw dislocations) that act as step sources since homogeneous nucleation of steps on the facet is expected to be negligible. Since voids in fine-line interconnects are often observed to be partially faceted, restricted void motion and resultant spreading which depend sensitively on crystallographic features, such as defect structure and grain orientation, may indeed limit the lifetime of fine-line interconnects in electronic devices.
Turnover of Texture in low rate Sputter-Deposited Nanocrystalline Molybdenum Films
Authors: Drüsedau Tilo P. , Klabunde Frank , Lohmann Mirko , Hempel Thomas , Bläsing Jurgen
Published: April 2011

The crystallite size and orientation in molybdenum films prepared by magnetron sputtering at a low rate of typical 1 Å/s and a pressure of 0.45 Pa was investigated by X-ray diffraction and texture analysis. The surface topography was studied using atomic force microscopy. Increasing the film thickness from 20 nm to 3 μm, the films show a turnover from a (110) fiber texture to a (211) mosaic-like texture. In the early state of growth (20 nm thickness) the development of dome-like structures on the surface is observed. The number of these structures increases with film thickness, whereas their size is weakly influenced. The effect of texture turnover is reduced by increasing the deposition rate by a factor of six, and it is absent for samples mounted above the center of the magnetron source. The effect of texture turnover is related to the bombardment of the films with high energetic argon neutrals resulting from backscattering at the target under oblique angle and causing resputtering. Due to the narrow angular distribution of the reflected argon, bombardment of the substrate plane is inhomogeneous and only significant for regions close to the erosion zone of the magnetron.
Hrem Study of Ultra Thin Titanium Films
Authors: Braisaz T. , Ruterana P. , Nouet G. , Komninou Ph. , Kehagias Th. , Karakostas Th. , Poulopoulos P. , Aggelakeris M. , Flevaris N. , Serra A.
Published: April 2011

High resolution electron microscopy has been used to characterize the structure of ultra thin films of titanium deposited on KBr substrate by Ultra High Vacuum (UHV) electron-gun evaporation. The size of the grains has an order of magnitude of 10 nm whatever the substrate temperature. The observations have been carried out along <1123> zone axis. Some of the grains contain planar defects which were identified as the twin {1011}. The atomic structure of this twin is characterized by a mirror plane similar to that observed in polycrystalline titanium. Additionaly, this structure can be modified by a b2/2 twinning dislocation.
Use of Malonic Acid in Chemical-Mechanical Polishing ( CMP ) of
Tungsten
Authors: Zhang L. , Raghavan S.
Published: April 2011

The use of malonic acid as an additive in alumina slurries used for the
chemical mechanical polishing ( CMP ) of tungsten has been explored for the
reduction of particulate contamination. The principal objective of this work
was to delineate conditions under which alumina contamination on polished
surfaces could be reduced.

The interaction between malonic acid and alumina particles has been
investigated through electrokinetic and adsorption measurements. At suitable
malonic acid concentrations and pH values, tungsten and alumina surfaces
develop a negative zeta potential resulting in conditions conducive to
reduced particulate contamination. Small scale polishing experiments have
been carried out to relate electrokinetic results to the level of
particulate contamination after polishing.
Post Metal Etch Treatment for Submicron
Applications
Authors: Gonzales Simon , Grivna Gordy , McAfee Anda
Published: April 2011

Corrosion control and passivation of post metal etch structures are critical
for submicron applications and overall yield performance. This study focused
on 0.6 micron metal line spaces and the development of a process utilizing
an integrated metal etch, photoresist strip and passivation tool. Data
collected to characterize the corrosion/passivation mechanism included: veil
and photoresist strip chemistries, passivation steps, time delays,
subsurface material versus veil formation and electrical and defectivity
yield. A post metal etch process was tested and integrated into a
manufacturing environment that has provided minimal line loss, complete
removal of etch veils, robust corrosion control and substantial reduction of
intermetal shorts.
Etching Characteristics During Cleaning of Silicon Surfaces by
NF3-added Hydrogen and Water-Vapor Plasma Downstream
Treatment
Authors: Suzuki Miki T. , Kikuchi Jun , Nagasaka Mitsuaki , Fujimura Shuzo
Published: April 2011

Hydrogen and water vapor plasma downstream treatment with the downstream
injection of NF3 removes native oxide from silicon surfaces. In
contact hole cleaning, this dry processing is a promising alternative to HF
wet treatment, which has a problem of expansion of hole diameter. We
examined the etching characteristics of boron-phosphosilicate glass (B-PSG)
films, as a typical oxide material for the side-walls of the contact holes
and compared the etching depths of B-PSG and thermal oxide films. We found
that the etching depths of B-PSG films fell to one third of those of thermal
oxide films at lower treatment temperature. This result indicates that the
expansion of contact hole diameters can be minimized.
SI3N4 Particle Removal Efficiency
Study
Authors: Liu Jane Qian , Lee Carolyn , Rosamilia Joseph M. , Boone Tom , Czitrom Veronica , Higashi Gregg S.
Published: April 2011

Controlling particle contamination in wafer cleaning is important to reduce
defect density and improve device performance and yield. In this study, a
screening experiment was employed to evaluate particle removal efficiency
among different cleanings, including FSI BCLN, bench rinse and dry only,
bench SC1/megasonic only, bench RCA cleaning, and bench RCA-based cleaning.
To optimize particle removal efficiency in RCA-based cleaning, a design of
experiment (DOE) has been done to investigate the impact of SC1/megasonic
cleaning on Si3N4 particle removal efficiency. Bath
temperature, megasonic power, and solution chemistry of SCI bath were
evaluated. The removal efficiency in relations to particle sizes was also
investigated
Comparison of High-Purity-Ozone Oxidation on Si(111) and
Si(100)
Authors: Kurokawa A. , Ichimura S. , Moon D. W.
Published: April 2011

The oxidation of Si(111) and Si(100) surfaces with the high-purity
ozone(more than 98 mole %) was investigated with X-ray photoelectron
spectroscopy (XPS). Thin oxide less than 3nm thickens was formed in an
experimental chamber and the results showed that ozone oxidizes the (111)
surface faster than (100) surface. Ozone does not show the temperature
dependence on oxidation within the temperature range of 250–500 degree C for
both (111) and (100) surfaces. Ozone proceeds the oxide formation at 700
degree C where oxygen does not proceed oxide formation rapidly.
State-of-the-Art Evaluation of Ultra-Clean Ulsi
Processes
Authors: Fischer-Colbrie A. , Laderman S. S. , Brennan S. , Ghosh S. , Takaura N. , Pianetta P. , Shimazaki A. , Waldhauer A. , Wherry D. , Barkan S.
Published: April 2011

This work describes recent progress in implementation and applications of
synchrotron radiation total reflection x-ray fluorescence (SR-TXRF) to
measure trace metals on wafer surfaces. To date, we have achieved
state-of-the-art transition metal sensitivity of 3×108
atoms/cm2 (˜3fg) for 1000 sec. counting time for impurities
which have an monolayer-like distribution on the surface and <1fg for
droplet-like impurities. Recent instrumentation breakthroughs include
reduction of detector parasitic backgrounds (particularly Cu) to below our
present detection limit, 150 and 200mm whole-wafer handling, wafer-mapping
capability and a cleanroom mini-environment. With these upgrades,
measurements were made of wafers from various steps in the integrated
circuit fabrication process. These results demonstrate that synchtron
radiation brings TXRF into a new and useful regime. Further developments are
underway to increase throughput and access for broader application.
Pulsed Laser Assisted Particulate Cleaning of Solid
Surfaces
Authors: Kumar D. , Ivory S. , Mahajan U. , Singh Rajiv K.
Published: April 2011

In the this paper, we have examined the particulate removal efficiency of
laser from solid surfaces. The silicon wafers were contaminated with alumina
particles with sizes ranging from 0.05 μm to 0.5 μm. The silicon wafers with
uniform surface-distribution of alumina particles were subjected to pulsed
laser beams at varying conditions. The results obtained have shown that line
beam lasers can remove submicron particles more efficiently from solid
surfaces. The mechanism responsible for higher particulate
removal-efficiency of line beam laser has also been discussed.