bluuebunny/crossref_metadata_2025 huggingface dataset:
Microstructures of Luminescent nc-Si by Excimer Laser Annealing of a-Si:H
Authors: Huang Xinfan , Wu Wei , Shen Honghui , Li Wei , Chen Xiaoyuan , Xu Jun , Chen Kunji
Published: April 2011

We have reported for the first time on visible photoluminescence (PL) in crystallized a-Si:H/a-SiNx:H multilayer structures by CW Ar ion laser annealing treatments. In this paper we present new results on visible PL from crystallized a-Si:H by using KrF excimer pulse laser (wavelength 248 nm) irradiating treatments. The transmission electron microscopy and Raman scattering studies reveal the microstructures of crystallized Si films, which depend on the pulse number and the pulse energy density of KrF laser. When the laser pulse energy density is higher than 520 mJ/cm2, the nanosized Si crystallites (nc-Si) can be formed from a-Si:H layers with a thickness of 100 nm and strong PL with a peak wavelength of 610 nm has been observed at room temperature.
Deposition of Photoluminescent Nanocrystalline Silicon Films by SiF4-SiH4-H2 Plasmas
Authors: Cicala G. , Bruno G. , Capezzuto P. , Schiavulli L. , Capozzi V. , Perna G.
Published: April 2011

Visible photoluminescence at 1.62 eV has been observed at room temperature from fluorinated and hydrogenated nanocrystalline silicon (nc-Si:H,F) produced in a typical plasma enhanced chemical vapor deposition system. The use of SiF4-SiH4-H2 mixture, because of the H2 dilution and the presence of SiF4, favours the amorphous - crystalline transition through the etching process of the amorphous phase. The x - ray diffraction measurements give an average grain size of about 100 Å. The presence of these nanocrystals shifts the absorption edge of the films towards higher energy. An energy gap of 2.12 eV is estimated, although the hydrogen content in the material is only 4.5 at. %. The temperature dependence of the photoluminescence behaves similarly to that of porous silicon.
Nanocrystalline Ge Synthesis by Picosecond Pulsed Laser Induced Melting and Rapid Soldddtcation
Authors: Solis J. , Siegel J. , Garcia C. , Jimenez J. , Serna R.
Published: April 2011

Melting and rapid solidification has been induced in DC-sputtered amorphous Ge (a-Ge) films on glass substrates by irradiation with picosecond laser pulses at 583 nm. The melting-solidification kinetics has been followed by means of real time reflectivity measurements with ns resolution and the structure of the rapidly solidified material has been analyzed by means of Raman spectroscopy in micro-Raman configuration. The results obtained show that for laser pulse fluences above a certain threshold recalescence occurs during solidification leading to the formation of nanocrystalline Ge embedded in an amorphous matrix. The phonon correlation length (L) obtained from the Raman spectra of the irradiated regions has been used to analyze the evolution of the crystallite size with the laser fluence. For low fluences above the recalescence threshold, the values of L are in the 8–10 nm range. However, if the fluence is sufficiently increased, the crystallite size shows a clear linear dependence on the fluence with phonon correlation lengths scaling from 6 to 13 nm.
Electrical Properties of the Multilayer Structures Based on Ultrathin Diamond-Like Carbon Films
Authors: Polyakov V. I. , Perov P. I. , Rossukanyi N. M. , Rukovishnikov A. I. , Khomich A. V. , Baranov A. M.
Published: April 2011

The electrical characteristics of multilayer structures based on amorphous ultrathin diamondlike carbon films were investigated including dynamic and quasi-static current-voltage characteristics, capacitance-voltage characteristics, deep level transient spectra. The effect of illumination and temperature on these characteristics was also investigated. For the multilayer structures composed of lower band gap amorphous carbon layers separated with higher band gap ones, there were observed well-defined regions of negative differential resistance and sharp 20-fold changes in capacitance at definite voltages. Activation energies, capture cross sections, and locations of trapping centers were defined. The effects observed are discussed in terms of trap-assisted tunneling and, also, in terms of resonant tunneling between energy levels in superlattices and charge filling of the quantum wells and trapping centers.
Nucleation and Growth of μc-Si:H n- and p-Type Layers in a-Si:H p-i-n AND n-i-p Solar Cells: Real Time Spectroellpsometry Studies
Authors: Koh Joohyun , Fujiwara H. , Wronskii C. R. , Collins R. W.
Published: April 2011

We have applied real time spectroellipsometry (RTSE) to study the growth of microcrystalline silicon n- and p-layers [μc-Si:H:(P,B)] incorporated into amorphous silicon (a-Si:H) p-i-n and n-i-p solar cells, respectively. In previous research, we have applied RTSE to characterize a-Si:H solar cells having only amorphous component layers. The μc-Si:H(P,B) component layers, however, pose a more difficult RTSE analysis problem for two reasons. First, the near-surface of the underlying i-layer is modified in the μc-Si:H:(P,B) growth process, and second, the microstructural evolution near the i/(n,p) interfaces is very complicated. From RTSE spectra (1.5 < hv < 4 eV) collected every ∼4–15 s during growth, we have extracted the time evolution of the μc-Si:H:(P,B) layer microstructure, thicknesses, and optical properties along with the modifications that the near-surface i-layer properties undergo in the formation of the i/(n,p) interfaces. We suggest that the beneficial optical properties of the microcrystalline layers may be due to size effects in the crystallites that make up the films.
Carbon Coated Nanoparticle Composites Synthesized in an RF Plasma Torch
Authors: Scott John Henry J. , Majetich Sara A. , Turgut Zafer , Mchenry Michael E. , Boulos Maher
Published: April 2011

FeCo alloy nanoparticles are synthesized in an RF plasma torch reactor and characterized using X-ray powder diffraction (XRD) and transmission electron microscopy (XRD). Bare, uncoated particles exhibit a chain-like agglomeration morphology marked by large ring- and bridge-like structures surrounding open voids. Acetylene was used to generate large numbers of carbon-coated nanoparticles similar to those produced in carbon arc reactors. Conventional TEM of this powder revealed numerous particles below 50 nm in diameter embedded in a carbonaceous matrix. These results establish RF plasma torch processing as a well-characterized, scalable alternative to carbon arc synthesis of encapsulated nanoparticles.
Synthesis of Nanocomposite thin film Ti/Al Multilayers and Ti-Aluminides
Authors: Banerjee R. , Zhang X. D. , Dregia S. A. , Fraser H. L.
Published: April 2011

Nanocomposite Ti/Al multilayered thin films have been deposited by magnetron sputtering. These multilayers exhibit interesting structural transitions on reducing the layer thickness of both Ti and Al. Ti transforms from its bulk stable hep structure to fee and Al transforms from fee to hep. The effect of ratio of Ti layer thickness to Al layer thickness on the structural transitions has been investigated for a constant bilayer periodicity of 10 nm by considering three different multilayers: 7.5 nm Ti / 2.5 nm Al, 5 nm Ti / 5 nm Al and 2.5 nm Ti / 7.5 nm Al. The experimental results have been qualitatively explained on the basis of a thermodynamic model. Preliminary experimental results of interfacial reactions in Ti/Al bilayers resulting in the formation of Ti-aluminides are also presented in the paper.
Lowered Diffusivity in TiO2 with a Nanophase Dispersion of SiO2
Authors: Crosbie Gary M.
Published: April 2011

In materials that are subject to environmental reactions, one way to increase durability is to decrease the chemical interdiffusion rate. In metal systems, mass transport by diffusion is enhanced – if any change – with finer grained microstructures, because of the greater number of high diffusion interface and boundary paths. In non-metals, increased transport is not necessarily the case, as other mechanisms may control the overall diffusivity. C. Wagner [1] showed the theoretical basis of transport in certain nanocomposite cases based on space charge layers at interfaces.

In an oxide-in-oxide nanocomposite, one can use the tools of bulk analysis to study the near-interface effects on transport. The immiscible pair, TiO2-SiO2, was used as a model system. Nanophase powders (50 and 200 m2/g, respectively) from flame hydrolysis were dispersed with high shear, then freeze-dried and hot-pressed to near theoretical density. Transmission electron microscopy was used to show < 10 nm particles in the composites produced at the time of diffusivity measurement. The rate of change of four-point electrical conductivity in response to a change in oxygen partial pressure was used to estimate chemical diffusivity. The re-equilibration differences between TiO2 diffusivity for bars of about 10 times different square cross-section areas confirmed the interpretation of the conductance rate changes to be the result of bulk interdiffusion.

The interdiffusion rate in the nanoscale dispersoid composites was more than 5 times lower than for same SiO2-fraction composites after coarsening which were like TiO2 with no second-phase. Results are in qualitative agreement with models for impurity segregation to interfaces and for space charge layers near the dispersed nanoparticles.
Nanocrystalline BaTiO3 from the Gas-Condensation Process
Authors: Li Shaoping , Eastman J. A. , Thompson L. J. , Bjormander Carl. , Foster C. M.
Published: April 2011

Nanocrystalline BaTiO3 can be prepared by the gas condensation method at a temperature as low as 700°C, with an average particle size as small as 18nm. The stoichiometry of nanocrystalline BaTiO3 particles can be controlled precisely and reproducibly. Nanocrystalline BaTiO3 powders, fabricated by a novel e-beam evaporation method, show good sintering behavior with a high density at a temperature as low as 1200°C. These samples exhibit a relatively larger dielectric constant than that of coarse-grained BaTiO3. In addition, a thermal analysis has been also carried out to determinethe lowest temperature for forming nanostructured BaTiO3 from Ba/Ti oxidized clusters at ambient pressure.
Physical and Chemical Properties of CaCl2/H2O and LiBr/H2O Systems Confined to Nanopores of Silica Gels
Authors: Aristov Yurii I. , Tokarev Mikhail M. , Cacciola Gaetano , Restuccia Giovanni , DiMarco Gaetano , Parmon Valentin N.
Published: April 2011

Here we present physical and chemical properties of CaCl2/H2O and LiBr/H2O systems confined to nanopores of silica gels. Sorption isobars, isosters and isotherms were measured at temperature 293 – 423K and vapor partial pressure 8–133 mbar. Specific heat of the systems was found as a function of temperature (300 – 400K) and sorbed water content (0 – 53 wt.%). Solidification/melting diagrams were measured over 170 – 320K temperature range at salt concentrations 0–50 wt.%. The results obtained evidenced a significant change in the thermodynamic properties of CaCl2/H2O and LiBr/H2O systems due to confinement to the silica gel micropores.
Carbon Black-Filled Polymer Blends: A Scanning Probe Microscopy Characterization
Authors: Leclère Ph. , Lazzaroni R. , Gubbels F. , Calberg F. , Dubois Ph. , Jérôme R. , Brédas J. L.
Published: April 2011

Conducting polymer composites, that consist of a conducting filler randomly distributed throughout an insulating polymer or polymer blend, attract interest in several application fields such as sensors or electromagnetic radiation shielding. The macroscopic electrical resistivity of the filled polyblend strongly depends on the localization of the filler. Here, we investigate the morphology of Carbon Black (CB)-filled polymer blends in order to determine the parameters governing the selective localization of CB in one phase of the blend components or at the interface between the components. The dispersion of the CB particles in the polymer blend is observed by means of Lateral Force Microscopy (LFM) as a function of the blend composition and the load in C.B. The selective localization of CB at the interface enables the reduction of the percolation threshold down to 0.5 wt%; as a result, the mechanical properties of the polymer blend can be fully retained. Different techniques can be used to locate the CB at the interface; we compare their efficiency experimentally.
Self-Assembly of Layered Aluminum Silsesquioxanes: Clay-Like Organic-Inorganic Nanocomposites
Authors: Ukrainczyk L. , Bellman R. A. , Smith K. A. , Boyd J. E.
Published: April 2011

A series of layered silicate-like structures with a wide range of Si/AI ratios that have an organic functionality directly bonded to the structural Si atom by Si-C bond were prepared by template sol-gel synthesis at room temperature and pressure. XRD patterns indicate that organic functionalities in the interlayers are in paraffin-like arrangement and do not interpenetrate. Structural ordering is primarily governed by the assembly of the organic functionalities into lamellar micelles. Nanocomposites were studied by solid state 29Si and 27AI NMR to determine the degree of condensation of inorganic framework. The results indicate that Si-O-Al linkages do not form in gels precipitated at low pH. Stable Si-O-Al linkages form when pH of the precipitates is raised. The highest degree of Si-O-Al bonding is obtained when Al solutions are prehydrolyzed prior to the addition of silane.
Temperature Dependence of Fracture Toughness of the Cubic (L12) Titanium Trialuminides
Authors: Varin R. A. , Zbroniec L.
Published: April 2011

Fracture toughness vs. temperature of the cubic (L12), Mn- modified titanium trialuminide (based on Al3Ti) was investigated in air at the temperature range up to 1000°C. Toughness calculated from the maximum load exhibits a broad peak (KQ≈7–10 MPara0,5) at the 200- 500°C temperature range and then decreases with increasing temperature, reaching a room temperature value of ∼4.5 MPam0.5 at 1000°C. However, the work of fracture (γWOF, J/m2) and the stress intensity factor calculated from it (KIWOF) increases continuously with increasing temperature. Fracture modes exhibit a gradual transition from transgranular cleavage at room temperature to predominantly intergranular failure at the 800- 1000°C range.
The Solid-Solution Alloying Effects of Ti on the High-Temperature Deformation Behavior of NiAl Single Crystals
Authors: Kitabjian P. H. , Garg A. , Noebe R. , Nix W. D.
Published: April 2011

We have investigated the high-temperature deformation behavior of the solid-solution strengthened alloy Ni-47.5Al-2.5Ti. Single crystals were deformed in compression in the “hard” <001> and “soft” <111> orientations, at temperatures between 900°C and 1200°C. The results show that Ti has a very powerful solute strengthening effect in NiAl. The creep rates for the solid-solution alloy were observed to be three to four orders of magnitude lower than for the stoichiometric material. We discuss our efforts to understand this solid-solution strengthening effect. We have studied high-temperature deformation transients in an effort to determine whether solute drag effects contribute to the creep resistance of this solid solution. In addition, we have examined the solute size effect of Ti as it replaces Al on the Al sub-lattice. We discuss the probable mechanism of creep of this alloy in light of TEM observations of the dislocation structures in creep-deformed crystals.
Dislocation Substructure in NiAl Single Crystals Deformed at Ambient Temperature
Authors: Shi X. , Pollock T. M. , Mahajan S. , Arunachalam V. S.
Published: April 2011

Dislocation substructure in NiAI single crystals oriented for single slip and deformed at ambient temperature has been studied using weak-beam transmission electron microscopy. Deformation is localized in bands that consists mostly of near-edge dislocations, with an interspersion of a high density of elongated prismatic loops. Pure screw dislocations are not observed, but dislocations having “zigzag” configurations that are near-screw in orientation are present. A high density of jogs is observed on both near-edge and zigzag dislocation segments. The mechanisms for the development of this substructure are discussed, emphasizing the role of double cross slip and resulting glissile and sessile jogs of varying heights.
Creep Behavior of MoSi2 with Si3N4 Reinforcements
Authors: Feng C. R. , Sadananda K.
Published: April 2011

Because of its high melting point, excellent oxidation resistance and ductility at high temperatures, MoSi2 and its composites are attractive for elevated temperature applications. In this study, the compression creep behavior of hot pressed MoSi2 with various volume fraction of Si3N4 at 1200°C, 1300°C and 1400°C were investigated. Within the stress range of 115–425MPa, the stress exponent, n, was either 1 or 5 depended on the volume fraction of Si3N4. The activation energy of creep for MoSi2-50%Si3N4 composite was 750kJ/mol. At still higher volume fraction of Si3N4, the activation energy decreases to 693kJ/mol, which is the same as that for monolithic Si3N4.
Nanometer-Scale Metal Dispersions in Polymeric Matrices
Authors: Shull K. R. , Cole D. H. , Rehn L. E. , Baldo P.
Published: April 2011

We have investigated the diffusive properties of model metal nanoparticle dispersions in polymeric matrices of several different molecular weights. Rutherford Backscattering Spectrometry was used to measure the depth distribution of gold nanoparticles within thin layers of poly(t-butyl acrylate) (PTBA). The gold nanoparticles were created by evaporation of a discontinuous gold layer onto a thin film of PTBA. A second PTBA film was placed onto these samples to create “sandwiches” in which the gold existed between two PTBA films. Gold particle diffusion coefficients were obtained from measured gold particle depth distributions in annealed samples for which the molecular weights of the two PTBA layers were identical. The experiments revealed that particle mobility was decreased by two to three orders of magnitude compared with the predictions of the Stokes-Einstein model of particle diffusion. These results are attributed to bridging interactions between particles arising from slow exchange kinetics of polymer segments at the polymer/metal interface. Experiments for which the molecular weights of the two polymer films are different are sensitive to the ability of polymer molecules to pass through the gold particle layer. Experiments done with thermally evaporated particles are consistent with a picture in which polymer molecules are able to freely pass through the gold particle layer. Results obtained with gold deposited by electron-beam evaporation are strikingly different. The gold in this case is not able to diffuse, and polymer molecules are not able to penetrate the gold layer. These results, in addition to preliminary results from optical absorption experiments, indicate that much smaller particles are obtained by electron-beam evaporation than by thermal evaporation.
Morphology of a Blend of Zinc Neutralized Sulfonated Poly(Phenylene Oxide) or Polystyrene and an Amino Silicone
Authors: Jones Alan A. , Inglefield Paul T. , Yang Changlai , Bergquist Pamela , Shi Jiefeng , Kambour Roger P. , Wignall George D. , Migeon Henri-Noel , Martin Jean-Paul
Published: April 2011

A polymer blend of an ionomer based on zinc neutralized sulfonated poly(phenylene oxide) or polystyrene with a silicone copolymer containing 6.45% propylamine groups in place of one of the methyl groups on a backbone silicon was prepared. Carbon-13 magic angle spinning spectra show coordination of the amine by the zinc ions. Morphological characterization was made by NMR spectroscopy based on proton spin diffusion, by small angle x-ray scattering and by energy filtered transmission electron microscopy. All experiments show domains in the range of 1 to 1000 nm and domain size can be controlled by the extent of coordination of the amine groups by the zinc ions and by thermal history. The different morphological experiments lead to an apparent hierarchy of domain sizes. The NMR experiment yields the smallest domains, 2 to 10 nm, where contrast is produced by differences in chain mobility. Small angle x-ray scattering indicates domains of 16 nm while electron microscopy indicates domains in the range of 100 to 1000 nm. The variation of the domain size between experiments may reflect the different sources of contrast in each case.
Lead and Silver Production in the Montevecchio Basin (Western Sardinia, Italy)
Authors: Ingo G.M. , Agus T. , Ruggeri R. , Amore Bonapasta A. , Bultrini G. , Chiozzini G.
Published: April 2011

Lead slags and lead pieces, chronologically related to the Punic and Roman periods (IV BC - II AC), have been found at Bocche di Sciria, in the basin of the Montevecchio mine (south-western Sardinia, Italy). Furthermore, along the coast of this area over than 20 Punic and Roman shipwrecks with charges of lead ingots have been found. These materials indicate intense pyrometallurgical activities and the presence of metal production centres very close to the metal ore deposits. The microchemical studies of the slags have shown that they can be associated to a smelting process for lead and silver production. Furthermore, lead isotope analysis has been carried out for lead ores from Montevecchio and for the lead slags, litharge, lead pieces found there. The results for lead ores are in good agreement with literature and the scatter of data for slags, litharge and lead pieces suggest to rule out a lead isotope fractionation in ancient lead and silver production.
Hrtem Studies of Dislocations and Interfaces in TiAl
Authors: Mills M. J. , Wiezorek J. M.K. , Fraser H. L.
Published: April 2011

In this paper, we summarize the results of high resolution transmission electron microscopy investigations of the structure of dislocations and interphase boundaries in Ti-Al alloys. Dislocations of the type 1/2<110] and 1/2<112] have been examined in 60° and 90° orientations, respectively, in single-phase Ti-52 at%Al. The former dislocation exhibits an extremely compact core configuration, suggesting a high complex stacking fault energy, while the latter is dissociated the scale of several nanometers in a coupled intrinsic/extrinsic stacking fault configuration. Two types of α2/γ interface structures have been observed in nearly fully-lamellar Ti-48 at%Al. The first is consistent with the common observation of structural ledges due to 1/6<112> dislocations in the interface plane. The second interface type consists of a quasi-periodic array of 1/2<110] dislocations which do not lie in the interface, and appear to be contained wholy within the γ phase. The possible implications of these observations with respect to the mechanical behavior of both single-phase γ and two-phase lamellar microstructures are discussed.
Time-Dependent Interfacial Reaction Mechanism in a Spinel-Forming Solid State Reaction Studied by TEM
Authors: Werner P. , Sieber H. , Huxebrand R. , Hesse D.
Published: April 2011

Interfacial reaction mechanisms were investigated in case of topotaxial formation of MgIn2O4 spinel on MgO crystals, which is an appropriate model system for thin film solid state reactions in ceramics. The reaction interface MgO/MgIn2O4(001), which is characterized by a large lattice misfit (+4.2%) between these cubic crystals, was investigated by transmission electron microscopy (TEM). Thin spinel films (thickness t< 0.5μm) consist of domains tilted off (≈3.5°) the exact cube-to-cube orientation into four directions, while thicker films (t> 1μm) show an accurate (001) orientation. High-resolution electron microscopy (HREM) showed that this time-dependent orientation behavior correlates with the atomic scale structure of the interface, especially with the different types of misfit dislocations. Based on these results, the misfit accommodation mechanism at the propagating reaction front in this spinel system is discussed including transitions between glide and climb processes.
Imaging the Dimers in Si (111) 7×7
Authors: Marks L. D. , Bengu E. , Plass R. , Ichimiya T. , Ajayan P. M. , Iijima S.
Published: April 2011

Recent work has demonstrated that high resolution electron microscopy in plan-view imaging mode is capable of directly imaging surfaces at a resolution of better than 2 Å. For the particular case of the Si (111) 7×7 surface, we have been able to image not only the adatoms visible in STM images, but all the atoms in the top three atomic layers including the dimers. The potential applications of this approach and its limitations will be discussed.
Application of Spatially Resolved Eels on Atomic Structure Determination of Diamond Grain Boundary
Authors: Ichinose H. , Zhang Y. , Ishida Y. , Ito K. , Nakanose M.
Published: April 2011

A new spatially resolved electron energy-loss spectrometry (EELS) method was introduced to obtain atomic structure information of grain boundaries in diamond thin films grown by chemical vapor deposition. The electron energy-loss spectra recorded from the grain boundary regions showed different feature near the energy loss corresponding to carbon ls-to-π* transition, as compared to the spectra recorded from neighboring crystalline regions. This difference was attributed to dangling bonds in atoms with planar three-fold coordination. A series of experiments are described in this paper that exclude any possible artifact in result interpretation.
Ring-Related Defects in MCZ Wafer Comparison by Electrical, Structural, and Device Properties
Authors: González F. , McQueen M. , Barbour R. , Rozgonyi G. A.
Published: April 2011

Thermal cycles in advanced CMOS processing can nucleate an annular ring of oxygen precipitate-induced stacking faults (OSF-ring) via activation of bulk nuclei grown-in during the crystal pulling process. Because the OSF-ring can adversely affect device characteristics, it is important that substrates with OSF-ring characteristics be detected early in the process. Results are presented in this paper from a typical DRAM device which show that the ring can act either in a beneficial gettering mode or as a device-degrading zone, depending on the depth distribution of the OSF-ring defects and the background iron impurity concentration.
Modeling Silicon Implantation Damage and Transient Enhanced Diffusion Effects for Silicon Technology Development
Authors: Giles Martin D. , Yu Shaofeng , Kennel Harold W. , Packan Paul A.
Published: April 2011

Despite more than 20 years of effort, detailed understanding of defect-coupled dopant diffusion in silicon still falls short of what is practically required to support state-of-the-art silicon technology development. The challenge for modeling in industry is to combine the best of our physical understanding with measurements of dopant profiles for technology-relevant conditions to provide models which are as predictive and efficient as possible. This paper presents experimental results which provide insight into damage generation and annealing processes and discusses practical modeling approaches to support technology development despite our incomplete understanding of the physical processes involved.
Helium Induced Cavities in Silicon: Their Formation, Microstructure and Gettering Ability
Authors: Kaschny J. R. , Fichtner P. F. P. , Muecklich A. , Kreissig U. , Yankov R. A. , Koegler R. , Danilin A. B. , Skorupa W.
Published: April 2011

The formation of cavity microstructures in silicon following helium implantation (10 or 40 keV; 1×1015, l×1016 and 5×1016 cm−2) and annealing (800 °C) is investigated by means of Transmission Electron Microscopy (TEM), Rutherford Backscattering Spectrometry and Channeling (RBS/C), and Elastic Recoil Detection (ERD). The processes of cavity nucleation and growth are found to depend critically on the implanted He concentration. For a maximum peak He concentration of about 5×1020 cm−3 the resulting microstructure appears to contain large overpressurized bubbles whose formation cannot be accounted by the conventional gas-release model and bubble-coarsening mechanisms predicting empty cavities. The trapping of Fe and Cu at such cavity regions is studied by Secondary Ion Mass Spectrometry (SIMS).
Chemical Trends in Electronic Properties of Gold-3D Transition Metal Impurity Pairs in Silicon
Authors: Justo J. F. , Assali L. V. C.
Published: April 2011

We report theoretical investigations of the chemical trends in the electronic properties of substitutional gold-interstitial transition-metal complexes in silicon. The results show that the stable pairs in trigonal symmetry are formed by a covalent mechanism which includes, besides Au and TM impurities, also the Si neighbors, rather than being derived from interactions between two electrostatically bound point charges.
Oxygen Gettering and Thermal Donor Formation at Post-Implantation Annealing of Hydrogen Implanted Czochralski Silicon
Authors: Ulyashin A. G. , Bumay Yu. A. , Fahrner W. R. , Ivanovo A. I. , Job R. , Palmetshofer L.
Published: April 2011

The effect of oxygen gettering by buried defect layers at post-implantation annealing of hydrogen implanted Czochralski (Cz) grown silicon has been investigated. Hydrogen ions were implanted with an energy of 180 keV and doses of 2.7.1016cm−2 into p-type Cz and for comparison into p-type float zone (Fz) Si. The samples were annealed at temperatures between 400 °C and 1200 °C in a forming gas ambient and examined by secondary ion mass spectrometry (SIMS) in order to measure the hydrogen and oxygen concentration profiles. Spreading resistance probe (SRP) measurements were used to obtain depth resolved profiles of the resistivity. The observed changes of the resistivity after post-implantation annealing of hydrogen implanted Cz and Fz Si can be explained by hydrogen enhanced thermal donor formation processes (oxygen or hydrogen related) and charges at the SiOx precipitates. The effective oxygen gettering in hydrogen implanted Cz silicon is attributed to hydrogen enhanced diffusion of oxygen to buried defect layers.
Influence of Underlayer and Encapsulation Process on Texture in Polycrystalline Silver Thin Films
Authors: Zeng Yuxiao , Zou Y. L. , Alford T. L. , DENG F. , Lau S. S , Laursen T. , Manfred Ullrich B.
Published: April 2011

The texture in polycrystalline Ag thin films prepared by e-beam evaporation has been characterized by an x-ray diffraction technique as a function of underlayers and encapsulation temperatures. The Ag films deposited on Ti layers showed a strong <111> fiber texture with a fiber axis parallel to the film normal, whereas an almost random orientation was observed in the Ag films on Cr layers. This underlayer dependence of texture is associated with the lattice match between Ag and underlayer metal. In addition to <111> texture, the Ag films on Ti also exhibited a <511> texture component, which is the result of twinning of <111> -oriented grains. After the encapsulation process, the <111> texture in the Ag films on Ti was significantly improved, as evidenced by an increased (111) diffraction intensity and a slightly narrower space distribution of the texture along the fiber axis. The highly textured Ag films are expected to exhibit an improved electromigration resistance.
Polycrystalline ZnO- and ZnO:Al-Layers: Dependence of film stress and Electrical Properties on the Energy Input During the Magnetron Sputtering Deposition
Authors: Ellmer K. , Cebulla R. , Wendt R.
Published: April 2011

Doped and undoped zinc oxide fims are widely used as transparent window and contact layers in thin film solar cells. Up to now the role of film stress on the layer and solar cell properties was not investigated in detail. In this paper the influence of the energy input from the magnetron sputtering plasma on the structural and electrical layer properties was investigated. The energy input during the deposition could be varied by using a simultaneous RF- and DC-excitation at a fixed sputtering pressure. The energy and the density of the ions bombarding the substrate at floating potential have been measured by a plasma monitor and by a Langmuir probe. Plasma monitor measurements displayed the different plasma potentials and ion energies at a floating substrate. While the DC-discharge is characterized by low plasma potentials and low ion energies, the RF-mode shows up to 2.5 times higher ion energies of EAr++ ≈ 50 eV.

The structural and electrical properties of doped and undoped ZnO-films, deposited with different RF/DC-power ratios can be explained by taking into account the different ion energies and densities during the deposition. Higher ion energies (RF-excitation) improve the structural quality and reduce the film stress, which decreases the specific resistance, both by a higher charge carrier mobility as well as higher carrier concentrations. The lowest resistivities and film stresses were ≈ 6–10-4 Ωcm and 0.5 GPa, respectively. Layers with different film stresses have been used to prepare CuInS2/CdS/ZnO-solar cells. Lower stress in the ZnO-films leads to higher cell efficiencies. For the first time, these results can explain why RF-sputtering is almost exclusively used for the window preparation of thin film solar cells.
The Microstructure and Electromigration Performance of Damascene-Fabricated Aluminum Interconnects
Authors: Besser Paul R. , Sanchez John E. , Field David P. , Anick Shekhar Pram , Sahota Kashmir
Published: April 2011

Novel metal deposition stack and damascene processing methods have been used to fabricate electrically isolated parallel arrays of 1.0 νm deep aluminum-alloy interconnect trenches varying in width from 0.5 μm to 16 μm. The grain size and crystallographic texture of the Al in these trenches has been characterized using transmission electron microscopy (TEM) and local electron backscattered diffraction (EBSD), respectively. Narrow lines (0.5 and 1.0 μm wide) have a bamboo microstructure, intermediate widths (2.0 μm wide) are nearly bamboo, and wide lines (4.0 μm and wider) are polycrystalline. The <111> texture of the lines degrades with decreasing linewidth. A secondary <100> component is demonstrated and its origin proposed. The electromigration reliability of the narrow damascene Al lines was measured, and the observed enhancement of damascene Al interconnects compared to conventionally-fabricated Al interconnects is correlated with the microstructure.
Microstructural Control of Amorphous Silicon Films Crystallized using an Excimer Laser
Authors: Viatella J.W. , Singh R.K.
Published: April 2011

The results of experiments using two techniques for microstructural control of laser-annealed silicon thin films on SiO2 substrates are given. In the first set, photolithographically fabricated single-crystal silicon seed wafers in intimate contact with the silicon films are used to show that it is possible to control nucleation location during laser annealing. Laser energy density was varied from 250–450 mJ/cm2 and the resultant microstructure was characterized using transmission electron microscopy (TEM). It was found to consist of four distinct regions. Areas adjacent to the seed consisted of grains with dimensions ∼ 0.5 μm. The surrounding region consisted of larger (∼ 1 μm) rectangular grains. A third region was observed sporadically and consisted of large (∼ 1.5 μm) rectangular grains adjacent to the latter region. The fourth region occurred several microns away from the contact and consisted of a fine-grained microstructure. In the second set, fine mesh (19 μm) masks were used to selectively crystallize regions in laser-annealed films. The resultant microstructure was characterized using TEM and was found to consist of large (∼ 1.5 μm) edge grains with smaller (∼ 0.8 μm) grains just inside of the edge grains. A theoretical discussion is presented to explain the observed phenomena in both experiment sets.
Improvement of Grain-Growth and Surface Roughness in Laser-Crystallized Polycrystalline Silicon Films
Authors: Choi H.-S. , Park C.-M. , Jeon J.-H. , Min B.-H. , Han M.-K.
Published: April 2011

The effects of nitrogen-radical treated amorphous silicon (a-Si) films on laser-crystallization behavior have been studied for the improvement of the grain-growth and the surface roughness. The radical treatments were performed by the rf (13.56 MHz) plasma-enhanced-chemical-vapor-deposition (PECVD) system with N2 gas before the laser-crystallization. The grain-size of the laser-crystallized polycrystalline silicon (poly-Si) film with 600 seconds of radical-treatment time was remarkably increased by the relaxation of solidification process caused by the possible evolution of solid phase SiNx compounds which shows the low thermal conductivity. The electrical conductivity at 30 °C was rather lager value of 3×10-5 Ω-1cm-1 than 1×10-5 Ω-1cm-1 of poly-Si without radical treatment, while the highly resistive SiNx compounds were formed. From the SEM images, the surface roughness was also improved by the selective etching of the 5%-water-diluted hydrofluoric (HF) acid on the grain boundaries which the SiNx compounds were well segregated into during the laser-crystallization.
Microstructure of and Crystal Defects in Nanocrystalline Tin Dioxide Thin Films
Authors: Pan X. , Zheng J.G.
Published: April 2011

Nanocrystalline SnO2 thin films, prepared by electron beam evaporation from high purity SnO2 and post deposition annealing in air at 700°C with different times, were investigated using HRTEM. The films are composed of nanocrystalline SnO2 crystallites and pores. Many of the crystallites consist of crystal defects, such as crystallographic shearing planes (CSPs), dislocations and twin boundaries (TBs). Atomistic structures of these defects were investigated. These defects interact with each other, resulting in different configurations of crystallites. The local composition at CSP and TB steps at dislocation cores varies with the type of dislocations and CSPs and is different from the stoichiometric composition of SnO2. Thus, the electronic structure at these defects is different from that of the perfect SnO2.
Atomie and Electron Structure of Diamond Grain boundaries in a Polycrystalline Film
Authors: Ichinose Hideki , Nakanose Megumi , Zhang Yaogan
Published: April 2011

A polycrystalline diamond film was grown on the polished surface of silicon substrate in H2-CO-O2 mixing gas. Atomic and electron structure of grain boundaries in the film was investigated by both high resolution electron microscopy and electron energy loss spectroscopy. CSL boundaries in the film showed characteristic feature in atomic structure; Σ 9 CSL boundary was parallel not to (221) plane but to (114) plane. A new line which correspond to π * state was found in addition to major σ * line in the EELS spectra of the boundary which contained three coordinate atoms. Observed π * line shows occurred change of a dangling bond (pz electron) to π state. No π * line appeared in the EELS spectra obtained from boundaries which contained no three coordinate atom such as (111) Σ 3 boundary.
The Integration of Interlayer Dielectric Deposition and Chemical
Mechanical Polishing
Authors: McAfee Anda , Koos Daniel A. , mcArdle Stephen , Jacobs Mercedes , Hiatt Robert
Published: April 2011

This paper addresses an important process issue in tie integration of
chemical mechanical polishing (CMP) with interlayer dielectric (ILD)
deposition for advanced back end processing. Gap fill between metal lines is
achieved by using a dep-etch-dep technique for the tetraethylorthosilicate
(TEOS) ILD deposition. The ILD layer is then planarized by CMP. Vias are
etched through the ILD and filled with tungsten plugs in a blanket tungsten
deposition and tungsten CMP sequence. Delamination has been observed at the
interface between the TEOS layers following the blanket tungsten deposition
and before or during tungsten CMP. The weak interface between the TEOS
layers was found to be the result of residual carbon and fluorine from the
tetraflouromethane (CF4) doped etch process. The interface between the TEOS
layers was examined using X-ray photoelectron spectroscopy (XPS) and atomic
force microscopy (AFM). Experiments were carried out to determine if the
residue and subsequent delamination could be eliminated by modifying the
dep-etch-dep process. An improved process was identified and has been
implemented on a 0.5μm CMOS and mixed-mode BiCMOS production line with no
subsequent occurrence of interfacial delamination.
‘Back end’ Chemical Cleaning in integrated Circuit Fabrication:
a Tutorial
Authors: Obeng Yaw S. , Raghavan R. S.
Published: April 2011

The applications of wet chemical cleaning at the ‘back-end’ of Integrated
Circuit (IC) or Metal-Oxide Semiconductor (MOS) fabrication are reviewed
from chemical, environmental and cost perspectives. The various classes of
commercially available “solvents” and “cryogenic” cleans are reviewed from
the perspective of process suitability, impact on device yield and waste
management. Strategies for minimizing processing concerns, as well as
alternatives to organic solvent based wet chemical processing will also be
discussed. Bulk photoresist (PR) stripping, post metal definition-, and post
window etch cleaning are used to illustrate the discussion.

The use of radiotracing as a diagnostic tool in understanding the mechanism
for metallic contamination during solvent cleans is also discussed. Data
suggesting how the chemistry and solvent composition affects alkali metal
(for example, sodium) contamination of dielectric- and barrier films during
IC processing will also be presented.
Minimization of Interfacial Microroughness for 13–60 Å Ultrathin
Gate Oxides
Authors: Sapjeta J. , Boone T. , Rosamilia J. M. , Silverman P. J. , Sorsch T. W. , Timp G. , Weir B. E.
Published: April 2011

By using a combination of smooth epi substrates (0.7 Å rms roughness),
in-situ UV/Cl2 processing, and rapid thermal oxidation, highly
reliable ultrathin gate oxides were produced with ≤ 1.0 Å rms interface
roughness.
Investigation of the Need for Alternative cleaning Chemistries for 30Å Gate Oxides
Authors: Bayoumi Amr , Fischer-Colbrie Alice , Parker Russ , Cox Mike , Greene Wayne
Published: April 2011

A comparative study of pregate cleaning solution chemistries has been conducted, for 30Å furnace oxides, to investigate the feasibility of continuing to use current cleaning technologies in this thickness range. The experiment focused on correlating changes of device properties with changes in chemistry. Several options were investigated for growing or etching the surface passivation oxide. Chemistries studied included standard SC1 (with Megasonic)/SC2, final HF, as well as room temperature single bath HF based chemistries (HF only, HF+H2O2, HF+HCl, HF+H2O2+HCl, SPM+HF). These chemistries were evaluated in terms of oxidation rate, metallic contamination from solutions, capacitance-voltage (CV) characteristics, and gate oxide integrity. Data suggest that furnace oxides can be reliably grown using conventional cleaning technology. HF-based mixtures might be justified for even more aggressive gate oxide thicknesses.
Analysis of Organic Contamination in Gases using Non-Volatile
Residue (NVR) Monitors and Time-of-Flight Secondary Ion Mass Spectrometry
(Tof-Sims)
Authors: Strossman G. S. , Lindley P. M. , Bowers W. D.
Published: April 2011

A methodology has been developed which provides a means of detecting and
chemically characterizing low levels of contaminants in process gases used
in the microelectronics industry. NVR monitors based on SAW (surface
acoustical wave) technology were exposed to cylinders of a common gas used
in microelectronics applications. A control cylinder of clean N2
was compared with a deliberately contaminated cylinder and two supposedly
clean cylinders from different suppliers. The SAW devices were able to
detect the residue deposited from each gas. After exposure to the cylinders,
the SAW devices were directly analyzed by time-of-flight secondary ion mass
spectrometry (TOF-SIMS) to identify the deposited residues. The TOF-SIMS
instrument was equipped with a liquid-N2 cooled sample stage to
facilitate detection of semivolatile species in the UHV environment
necessary for the analysis.
Effect of Sheet Electron-Beam Irradiation (SEBI) on Water
Wettability of Mirror-Finished Si Wafer
Authors: Mori K. , Okada T. , Oguri K. , Nishi Y.
Published: April 2011

The influence of sheet electron beam irradiation ( SEBI ) on the
water-wettability of the ( 100 ) plane on the Si wafer etched by
hydrofluoric acid ( HF ) is investigated. The wettability energy is
estimated from the contact angle of water. The SEBI treatment decreases the
contact angle and increases the interfacial energy. Aging decreases the
change in the interfacial energy. A rate process is inferred for the
interfacial energy changes on the Si wafer.
Cleaning Process Optimization in a Gate Oxide Cluster Tool Using
an in-Line XPS Module
Authors: Froeschle Barbara , Glowacki Frédérique , Bauer Anton J. , Kasko Igor , Oechsner Richard , Schneider Claus
Published: April 2011

A cleaning process using anhydrous HF (AHF)/methanol and ozone was carried
out in a STEAG AST Vapor Phase Cleaning module (VPC). This module was
integrated in a state-of-theart cluster tool also consisting of a STEAG AST
Rapid Thermal Oxidation module (RTO). To investigate the properties of
silicon after cleaning a novel in-line XPS module was integrated into the
gate oxide cluster. Measurements of fluorine, carbon, and oxygen
contamination in the range from 0.01 to 1 monolayers on cleaned wafer
surfaces and on regrown oxides (< 0.5 nm) have been performed and used
for rapid optimization of the cleaning procedure. The in-line integration
enabled measurements without exposing the wafers to atmosphere thus avoiding
oxidation or contamination of the wafer surfaces. To demonstrate the
feasibility of this cluster tool for advanced gate dielectric formation, 4.0
nm thin oxide was grown directly after the cleaning in the RTO module
without breaking the vacuum. Time dependent dielectric breakdown results for
oxides pre-oxidation-cleaned in AHF, and in AHF followed by ozone were
compared to a reference sample without any dry pre-oxidation cleaning. It
could be shown, that the cleaning in AHF with a subsequent ozone step at
200°C under UV light lead to improved breakdown characteristics compared to
AHF/methanol cleanings without such subsequent ozone/UV step or conventional
wet cleaning using HF-Dip.
Silicon Surface Metal Contamination Measurements using
Grazing-Emission XRF Spectrometry
Authors: De Gendt S. , Kenis K. , Baeyens M. , Mertens P. W. , Heyns M. M. , Wiener G. , Kidd S. J. , Knotter D. M. , De Bokx P. K.
Published: April 2011

Grazing-Emission X-Ray Fluorescence Spectrometry (GEXRF) is a new analytical
X-ray fluorescence technique, which like TXRF takes advantage of the
total-reflection phenomenon. The main advantage of GEXRF over TXRF is its
sensitivity towards light elements. This paper presents straight GEXRF and
VPD-DC-GEXRF analysis results for Na, Mg, Al, K and Ca surface contamination
on silicon wafers.
Ozone Cleaning of Carbon-related Contaminants on Si Wafers and
other Substrate Materials
Authors: Nonaka H. , Kurokawa A. , Ichimura S. , Moon D. W.
Published: April 2011

We have investigated a novel surface cleaning technique of native oxide on
Si wafer, in which carbon-related contaminants are removed effectively at
room temperature with a pure ozone beam from an ozone jet generator that we
developed. Although ozone alone was likely to be little reactive to
saturated carbons and byproducts in the reaction of ozone with unsaturated
carbons which could be assigned to either carbonyl- or carboxyl-related
compounds, a high-dose pure ozone under ultraviolet light irradiation to
generate atomic oxygen by the photo-dissociation of ozone removed most of
them at room temperature. The effectiveness of the ozone cleaning was also
demonstrated for selected oxide surfaces.