bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Role of Lamellar Interfaces on the Strength and Ductility of Two-Phase Titanium-Aluminum
Authors: Wiezorek Jürg M. K , Dong Xiao Dong , Mills Michael J. , Fraser Hamish L
Published: April 2011

The deformation mechanisms active in hard orientation compressed pst-TiAl have been studied by transmission electron microscopy (TEM). The observed deformation modes involved soft superdislocation and hard ordinary dislocation slip, and hard twin systems. The transfer of these twin shears occurred across all types of (γ/γ)-interfaces. Transfer mechanisms have been determined on the basis of crystallographic analyses of the TEM data. The active modes of deformation were consistent with macroscopic shape changes observed for the pst-TiAl when the twin shear transfer mechanisms were considered. Based on these observations it has been proposed that the strength and ductility of polycrystalline fully-lamellar TiAl may be improved by reducing the width of both γ- and α2-lamellae.
Ductility and Fracture of FeAl: Effects of Composition and Environment
Authors: Cohront J. W. , Lin Y. , Zee R. H. , George E. P.
Published: April 2011

In ultrahigh vacuum (UHV), the ductility of FeAl decreases with increasing Al content and fracture becomes increasingly intergranular. Boron improves ductility by segregating to the grain boundaries and suppressing grain-boundary fracture. However, with increasing Al concentration, even the B-doped alloys become brittle and fracture intergranularly. Hydrogen gas at low pressures embritties FeAl, although not as severely as atmospheric moisture. Ductility is highest in UHV followed by that in O2, vacuum, and air.
Effect of A12Ti Phase on Plastic Behavior in Ti-62.5at%Al Single Crystals
Authors: Nakano Takayoshi , Hayashi Koutarou , Ashida Keishi , Umakoshi Yukichi
Published: April 2011

The microstructure and plastic deformation behavior in Ti-62.5at.%Al single crystals were investigated focusing on effect of the formation of h- and r-AI2Ti precipitates. Crystal structure, morphology and volume fraction of the precipitates depended strongly on the annealing temperature. The r-A12Ti phase precipitated as a plate in the Li0 matrix containing A15Ti3 superstructure below 1200°C, while the h-Al2Ti phase appeared at the higher temperature. The r-A12Ti had six-fold periodicity along the c-axis of the L10 structure and formed a semi-coherent boundary with the matrix maintaining an orientation relationship with {101)r-A12Ti//{101)L10 In contrast, small particles of h-A12Ti with three-fold periodicity along the b-axis were homogeneously distributed in the matrix forming an obscure coherent phase boundary.

Yield stress for specimens with a [201] loading axis anomaly increased showing a maximum peak around 800°C and then rapidly decreased. [111] <110] slip was dominant in the Li0 matrix and research-article-Al2Ti precipitates at temperatures below the peak, while slip occurred on (001) above the peak temperature. The anomalous strengthening and the change in operative slip system were discussed focusing on the effect of anisotoropy of APB energy and formation of Al2Ti precipitates.
Determination of the Effect of Hf Additions on Phase Stability in Nb-Silicide Based In-Situ Composites
Authors: Bewlay B. P. , Zhao J.-C. , Jackson M. R. , Bishop R. R.
Published: April 2011

In-situ composites based on Nb-Si alloys are potential candidates for application as structural materials in future aircraft engines. In order to achieve the balance of properties that is required, additional alloying species, such as Ti, Hf, Mo, Cr, Al, are employed. The present paper describes the effect of Hf additions on phase stability of Nb-Si alloys. Liquid-solid and solid-state phase equilibria have been investigated. The Nb-Hf-Si liquidus surface and the isothermal section at 1500°C will be described. A broad range of Nb and Hf compositions were investigated for Si concentrations up to 35.0%.
Effect of Additives on Eutectoid Reaction and Mechanical Properties of Nb-Nb5Si3 Alloys
Authors: Miura Seiji , Saeki Yasuhiko , Mohri Tetsuo
Published: April 2011

For the improvement of mechanical properties, especially ductility, of intermetallic compoundbased alloys, microstructural control has been adopted to binary and higher-order systems. Although lamellar structure formed by a eutectic reaction has been attracting broad attention to ductilize alloys with a combination of brittle/ductile or brittle/brittle phases, it should be pointed out that the microstructure such as lamellar size or colony size is hard to be controlled after the solidification process. In that viewpoint, high-temperature solid-solid phase transformation provide significant advantages in handling and large super-cooling for the control of lamellar structure through eutectoid reaction.
Fine Structures of the Pyramidal Slip Dislocations in Ti3Al Single Crystals at Temperatures of the Yield Stress Anomaly
Authors: Minonishi Yasuhide
Published: April 2011

The <1126>(1121) pyramidal slip in Ti3Al shows the so-called yield stress anomaly. A marked change in dislocation configuration is observed in the temperature range concerned; dislocations observed at the lowest temperature of the range, −70°C, are ordinary pairs of edge c+a/2 superpartial dislocations coupled by antiphase boundaries (APBs) while at the other extreme temperature 700°C, pairs of unlike superpartials coupled by APBs are observed. The change in dislocation configurations is interpreted as resulting from immobilization of edge c+a/2 superpartial segments by climb dissociation onto the basal plane.
Internal Friction in Plastically Deformed High-Purity NiAl Single Crystals
Authors: Hirscher M. , Schaible D.
Published: April 2011

High-purity stoichiometric NiAl single crystals have been prepared by crucible-free inductive zone melting and afterwards well annealed at temperatures below 1200 K. Internal friction measurements of torsionally deformed single crystals show two relaxation maxima at 500 and 800 K which anneal during the measurement. The first maximum can be assigned to the dislocation motion by kinkpair formation and the annealing to pinning of these dislocations by interstitial impurity atoms. The second maximum is attributed to the Snoek-Köster relaxation of dislocations in the presence of mobile interstitial impurity atoms and the annealing to the pinning of dislocations by vacancies. The kink-pair formation enthalpy in NiAl was estimated.
First-Principles Total Energy Study of NbCr2 + V Laves Phase Ternary System
Authors: Ormeci Alim , Chen S. P. , Wills John M. , Albers R. C.
Published: April 2011

The C15 NbCr2 + V Laves phase ternary system is studied by using a first-principles, self-consistent, full-potential total energy method. Equilibrium lattice parameters, cohesive energies, density of states and formation energies of substitutional defects are calculated. Results of all these calculations show that in the C15 NbCr2 + V compounds, V atoms substitute Cr atoms only.
Smart Oxygen Diffusion Barrier Based on IrAl Alloy
Authors: Hosoda Hideki , Watanabe Sadao , Hanada Shuji
Published: April 2011

Ir should be used as an effective oxygen diffusion barrier (ODB) for ultrahigh temperature structural materials since If exhibits extremely low oxygen diffusivity. Oxidation resistance of Ir is, however, not good due to formation of gaseous oxide, IrO3, over 1390K. In this study, the improvement of oxidation resistance was aimed through alloy design of alloying with Al. IrAl is expected to form a self-healing multifunctional layered structure composed of Ir layer as ODB and A12O3 layer as a protective oxide (PO) on the Ir layer. Ar arc-melted IrAl alloy was crushed into powder, followed by hot pressing and heat treatment to remove Ir formed by eutectic reaction. Oxidation behavior was measured using thermogravimetry (TG) and differential thermal analysis (DTA) under the conditions of (1) dynamic heating of 0.167K/s and (2) isotherms at 1273K to 1673K in O2 environment. It was found that oxidation resistance is much improved by alloying with At and that the designed structure (PO/ODB) is formed on the IrAl substrate. Compressive mechanical properties were investigated from RT to 1873K: both the strength as a function of normalized temperature and specific strength are higher than those of pure Ir, NiAl, TiAl and Ni3A1. IrAl is promising as a advanced smart coating material equipping good oxidation resistance as well as high temperature strength.
Modifications 7 And 8 Of Decagonal AI-Co-Ni
Authors: Ritsch S. , Hiraga K. , Beeli C. , Gödecke T. , Scheffer M. , Lück R.
Published: April 2011

Besides the six established decagonal states of the Al-Co-Ni quasicrystal two more modifications have been discovered by means of transmission electron microscopy. One is a pentagonal quasicrystal with a superstructure found in specimens with a very high Co-content and quenched from the highest possible temperature lying within the stability field of decagonal Al-Co-Ni. Its electron diffraction patterns are characterized by a 5-fold rotation axis as a unique symmetry element as well as superstructure reflections similar to those of a related decagonal phase. The other is a one-dimensional quasicrystal closely related to decagonal Al-Co-Ni. The modulation length of 61 Å along the periodic direction in its pseudo 10-fold diffraction patterns can be assumed to be caused by a strong linear, uniform, phason strain in the material.
Application Of Quasicrystalline Materials As Thermal Barriers In Aeronautics And Future Perspectives Of Use For These Materials
Authors: S´nchez A. , García de Blas F. J. , Algaba J. M. , Alvarez J. , Vallés P , García-Poggio M. C. , Agüero A.
Published: April 2011

Quasicrystalline materials (QCs) have very interesting properties which make them good candidates to be used as coatings resistant to wear, high temperature oxidation, corrosion, etc. The potential application of AI71Co13Fe8Co8 (QC1), a quasicrystalline approximant alloy, as a thermal barrier coating (TBC) for components of aeronautical and power generation turbines was explored in our laboratories and the results are presented in this paper. QC1 is stable at I 1000°C and has a thermal conductivity similar to that of yttria stabilized zirconia (YSZ), the most commonly used material for TBCs. QC1 powders were low pressure plasma sprayed on IN100 superalloy and coatings of excellent quality were obtained after a series of optimization experiments. The “as deposited” coatings were characterized by XRD, SEM and TEM and the results indicated that the coatings retained the same microstructure and phase composition as the bulk material. However, when coated specimens were heat treated at 950°C, interdifussion between coating and substrate took place resulting in the transformation of the QC approximant phase. To avoid or retard this process, the effect of several diffussion barrier layers, deposited between substrate and coating, was studied and the results showed that some of these barriers were quite efficient in slowing the diffusion process. Extensive cyclic oxidation and hot corrosion studies were carried out, showing promising results for this new type of TBC coatings. A short term ground engine test was carried out with coated blades.
Development Of High-Strength Aluminum-Based Alloys By Synthesis Of New Multicomponent Quasicrystals
Authors: Inoue A. , Kimura H. M.
Published: April 2011

By the control of composition, clustered atomic configuration and stability of the supercooled liquid in the rapid solidification and powder metallurgy processes, high-strength Al-based bulk alloys containing nanoscale nonperiodic phases were produced in AI-Ln-LTM, AI-ETM-LTM and Al-(V, Cr, Mn)-LTM (Ln=lanthanide metal, LTM=VII and VIII group metals, ETM=IV to VI group metals) alloys containing high Al contents of 92 to 95 at%. The nonperiodic phases are composed of amorphous or icosahedral (I) phase. In particular, the Al-based bulk alloys consisting of nanoscale I particles surrounded by Al phase exhibit much better mechanical properties as compared with commercial Al base alloys. The success of producing the Al-based alloys with good engineering properties by use of I phase is important for future development of I-based alloys as practical materials.
12.1” Svga Wide Viewing Angle Tft-Lcds Based on Ridge and Fringe-Field Structures
Authors: Lien A. , Cai C. , John R. A. , Galligan E. , Nunes R. , Wilson J. , Ifill H.
Published: April 2011

We have recently proposed the ridge and fringe-field multi-domain homeotropic (RFF-MH) mode for improving viewing angles of thin-film-transistor driven liquid crystal display (TFT-LCD) panels (4). We also demonstrated that the RFF-MH structures are suitable for high resolution desk top TFT-LCD panels (5). In this paper we demonstrated that the RFF-MH method is also suitable for the high-end large-area notebook application since it provides wide viewing angles with a high optical transmission. The ridge structure is constructed on top of the indium tin oxide (ITO) layer of the color filter (CF) substrate, and can be fabricated during the color filter process. The cell process of the RFF-MH panel is compatible to the conventional TFT-LCD cell fabrication process. It requires one extra photolithographic step; however no rubbing treatment is required.
Electron Diffraction Investigation of Crystallographic Texture of Thin Films
Authors: Tang Li , Duan Shanlin , Laughlin David E.
Published: April 2011

A method of investigating thin film crystallographic texture by electron diffraction is reviewed. The reciprocal lattices of fibrous and lamellar textured thin films are spherical belts around the texture axis. Equations describing the projection of the spherical belts onto the Ewald sphere along the texture axis direction are presented. Based on these equations the geometric and intensity evolution of the electron diffraction patterns with the tilt angle about an arbitrary axis in the film plane can be analyzed in a systematic way. The geometric characteristics of the electron diffraction patterns are then used to derive the texture axis directional index and its angular distribution. The way to determine the equal-intensity circular arcs on the diffraction pattern is also discussed. This method can be applied to both single layered and multilayered thin films of various applications.
Lattice Parameter Determination of Textured Co81−xCr15PtxTa4 Thin Films
Authors: Lu B. , Harkness S. D. , Lewis W. A. , Laughlin D. E. , Lambeth D. N.
Published: April 2011

The thin films Co81−xCr15PtxTa4 with (0002) crystallographic texture have been sputter deposited with and without substrate bias. The lattice parameter of the thin films has been determined by a combination of x-ray diffraction and electron diffraction techniques. The resolution of the electron diffraction was enhanced by a digital imaging technique. The variation rate of the a lattice parameter with Pt content is consistent with Vegard's law. The change in the c lattice parameter is much greater than what is expected from Vegard's law.
Dislocation Tunneling in Plastically Deformed Aluminum
Authors: Thompson Eunjoo , Pohl R. O.
Published: April 2011

We have measured the amplitude dependent internal friction (ADIF) and sound velocity down to 0.065 K of a 99.9999% (6N) aluminum that was plastically deformed by 1%. The strain amplitude was varied from ε = 1 × 10−8 to ε = 6 × 10−7, a factor of 60. It is observed that with increasing strain amplitude, both the internal friction and the sound velocity become temperature independent over an increasingly wider temperature range. ADIF measurements show a flattening of the temperature dependence of the strain amplitude at low temperatures which is taken to be strong evidence for dislocation tunneling.
C-Axis Perpendicularly Oriented Barium Ferrite Thin Film Media on Silicon Substrate
Authors: Zhuang Zailong , Kryder Mark H. , White Robert M. , Laughlin David E.
Published: April 2011

Barium ferrite thin films with excellent perpendicular c-axis orientation were successfully fabricated on Si substrate without any buffer layer. To compensate for possible barium deficiency due to the inter-diffusion between films and substrate, a barium-rich target was used. For a 900 Å-thick film, the perpendicular remanent squareness is about 0.9, while the in-plane remanent squareness is about 0.3. The saturation magnetization (Ms) is about 220 emu/cc, while the coercivity is around 3500 Oe. X-ray diffraction (XRD) results show the (001) perpendicular c-axis texture in the films. It was also found that the rapid thermal annealing conditions greatly affect the magnetic properties of barium ferrite films. With a certain flow rate of oxygen gas in the rapid thermal annealer (RTA), barium ferrite films generally crystallize with good perpendicular c-axis texture. Without oxygen gas, the hexagonal barium ferrite phase fails to develop; instead spinel Fe3O4 phase forms. The reason for the collapsing of hexagonal barium ferrite texture is thought to be an oxygen deficiency in the barium ferrite films due to the reduction of oxygen in the films during the high temperature annealing.
Investigations on in situ Nanocrystallization and Magnetic Properties for Amorphous Fe78Si9B13 Ribbons
Authors: Sun Xiangcheng , Cabral-Prieto A. , Yacaman M. Jose , Sun Wensheng
Published: April 2011

The amorphous state of ferromagnetic Fe78Si9B13 (Metglas 2605S-2) and itsnanocrystallization were investigated by in situ transmission electron microscope (TEM), Xraydiffraction (XRD), Mossbauer spectroscopy (MS), differential scanning calorimeters(DSC) and magnetic moment measurements. The Mössbauer spectrum exhibited anessentially symmetric hyperfine field pattern of 259KOe in as-quenched amorphous state atroom temperature. The Curie and crystallization temperature were determined to beTc=708K and Tx.= 803K, respectively. The Tx value was in good agreement with DSCmeasurement results. The occupied fraction of the nanocrystalline phases of α-Fe(Si) andFe2 at in situ optimum annealing temperature was about 57% and 43%, respectively. It isnotable that the magnetization of the amorphous phase decreases more rapidly withincreasing temperature than those of nanocrystalline ferromagnetism, suggesting thepresence of the distribution of exchange interaction in the amorphous phase or highmetalloid contents.
Structure and Sensor Properties of a Robust GMR Material System
Authors: Lenssen K.-M. H. , Donkers J. J. T. M. , Kuiper A. E. T. , Driel J. VAN
Published: April 2011

Recently we have developed a robust GMR material system, based on an artificial antiferromagnet which is exchange-biased with Ir-Mn. By combining magnetoresistance and magnetization measurements with Transmission Electron Microscopy analyses we show that the degree of [111] texture has direct effects on the sensor properties of the GMR multilayer. The degree of texture turns out to depend not only on the buffer layer, but also on the thickness of the Ir-Mn layer. The strongest texture is found for Ir-Mn layer thicknesses of around 4 nm. For this thickness the largest exchange-biasing field and GMR ratio are also obtained (after cooling in a magnetic field), but the blocking temperature is significantly reduced. If attention is paid to the material structure by choosing the right materials, layer thicknesses and stack order, a robust GMR multilayer system can be made that can withstand high temperatures (> 200°C) and strong magnetic fields (> 200 kA/m), as has been demonstrated experimentally.
Electrodeposition of NiFe Thin Films and NiFe/Cu Multilayers with a Recirculating Electrochemcial Flow Reactor
Authors: Myungl N. V. , Ryu K. H. , Kim J. H. , Schwartz M. , Nobel K.
Published: April 2011

Nano-structured Ni80Fe20NCu multilayers were electrodeposited by a newly developed electrodeposition process utilizing a recirculating electrochemical flow reactor. This process, which operates in an inert gas environment, overcomes the limitations of conventional multilayer electrodeposition methods (single and dual bath techniques) by depositing pure magnetic layers without codeposition of the nonmagnetic metal and oxidation of metal interfaces. Structure, corrosion resistance and magnetic properties of electrodeposited NiFe (0 to 100 % Fe) thin film alloys were first investigated. Three different crystal regions, α, mixed α and γ, and γ phases were observed at <50,;50, >50 % Fe in the deposit, respectively. The narrow mixed phase regions was around 50 % Fe compared to 70–80% Fe for bulk alloys. The lattice parameters of electrodeposited alloys exhibited the same trends as bulk alloys. Maximum corrosion resistance was obtained at 50% Fe content in 0.5 M NaCl similar to bulk alloys. The corrosion resistance of the α phase was an order of magnitude less than the γ phase. The magnetoresistance (MR) of electrodeposited NiFe thin film alloys was higher than bulk alloys. Based on these studies, Ni80Fe20/Cu multilayers with individual layer thicknesses ranging from 100 nm to 1.26 μm have been electrodeposited in the recirculating electrochemical flow reactor. The layer thicknesses were precisely controlled by adjusting the amount of charge passed.
Modelling the influence of pad bending on the planarization performance during CMP
Authors: Grillaert Joost , Meuris M. , Vrancken E. , Heylen N. , Devriendt K. , Fyen W. , Heyns M.
Published: April 2011

One of the major problems with oxide-CMP is the oxide thickness variation after CMP within one die, the socalled Within Die Non-Uniformity (WIDNU). The variations in pattern density of the design layout causes different local removal rates across the die resulting in the WIDNU. In this paper we shown that this is influenced by the pad stack. Depending on the thickness of the top pad the WIDNU can be reduced from about 470 nm until almost zero. This will be related to the bending of the top pad. The modelling will focuss on the two extreme cases of perfect pad bending and no pad bending.
XPS and Electrochemical Studies on Tungsten-Oxidizer Interaction in Chemical Mechanical Polishing
Authors: Tamboli Dnyanesh , Seal Sudipta , Desai Vimal
Published: April 2011

Electrochemical interaction between the oxidizer and the metal is believed to play a key role in material removal in tungsten CMP. In this study, we use X-ray Photoelectron Spectroscopy (XPS) in conjunction with electrochemical measurements in both in-situ polishing conditions as well as in static solutions, to identify the passivation and dissolution modes of tungsten. Dissolution of tungsten oxides was found to be the primary non-mechanical tungsten removal mechanism in CMP.
Single Wafer CVD of Silicon Nitride for Cmos Gate Applications
Authors: Pomarede C. , Werkhoven C. , Weidmann J. , Bergman T. , Gschwandtner A. , Houssa M.
Published: April 2011

The MESC/CTMC compatible, Advance 2500 cluster tool made by ASM is evaluated for the manufacturing of CMOS gate stack structures based on CVD silicon nitride rather than thermally grown silicon oxide as the gate dielectric material, and polysilicon as the gate electrode material. With two different CVD chemistries excellent growth characteristics and thickness uniformity control of the silicon nitride is demonstrated. Electrical assessment reveals lower leakage current as compared to silicon oxide and minimal hysteresis in C-V curves, even for gates stacks that have an equivalent oxide thickness below 1.5nm. The best properties are for silicon nitride films that also have a low H2 content.
Ultra-Thin High Quality Silicon Nitride Gate Dielectrics Prepared by Catalytic Chemical Vapor Deposition at Low Temperatures
Authors: Sato Hidekazu , Izumi Akira , Matsumura Hideki
Published: April 2011

This is to report the feasibility of ultra-thin silicon nitride (SiNx) films, prepared by catalytic chemical vapor deposition (Cat-CVD) method, as an ultra-thin gate insulator. In the Cat-CVD method, the deposition gases such as a gaseous mixture of silane (SiH4) and ammonia (NH 3) are decomposed by catalytic cracking reactions with a heated tungsten catalyzer placed near substrates, and SiNx films are formed at substrate temperatures around 300°C without using plasma. In the paper, additionally the effect of post-deposited treatments by using NH3-decomposed species or hydrogen (H2)-decomposed species formed by catalytic cracking of NH3 and H2 are also studied. It is found that a small hysteresis loop is seen in the C-V curve of as-deposited Cat-CVD SiNx films and that the leakage currents with thickness of 3nm equivalent oxide thickness (EOT) is slightly larger than that in the conventional thermal SiO2 of similar EOT. However, it is also found that the properties of Cat-CVD SiNx films are drastically improved by the post-deposited H2 or NH3 treatments, that is, the hysteresis loop disappears and the leakage current decreases by three orders of magnitude.
The Effects of Interfacial Suboxide Transition Regions on Direct Tunneling in Oxide and Stacked Oxide-Nitride Gate Dielectrics
Authors: Yang H. , Niimi H , Wu Y. , Lucovsky G.
Published: April 2011

Mesarjian et al. were the first to recognize the effects of suboxide interfacial transition regions at Si-SiO2 interfaces on tunneling oscillations in the Fowler-Nordheim regime. This paper extends these ideas to the direct tunneling regime and focuses on differences in interfacial transition regions between Si-SO2 interfaces with, and without monolayer level interface nitridation. Tunneling currents in both the direct and Fowler-Nordheim tunneling regimes are reduced by monolayer level interface nitridation for PMOS and NMOS devices with the same oxide-equivalent thickness. This paper develops a modified barrier layer model based on analysis of XPS results that accounts for these reductions in current in the direct tunneling regime.
Low-Temperature Formation of SiO2 and High Dielectrics Constant Material for ULSI in 21st Century
Authors: Ohmi Tadahiro , Sekinet Katsuyuki , Kaiharat Ryu , Saitot Yuji , Shirai Yasuyuki , Hirayama Masaki
Published: April 2011

A high-density plasma processing system featuring a radial line slot antenna has been developed for high-quality thin film formation at low temperature. This system is characterized by a high plasma density (above 1012 cm−3), a low electron temperature (below 1 eV) and a low plasma potential (less than 9 V). High-integrity silicon oxide films grown by direct oxidation of silicon surface at 400°C have been developed by introducing oxygen radical oxidation where oxygen radicals are obtained by a high-density plasma in He/O2 ambient. It is confirmed that the breakdown field intensity of oxide film is more than 15 MV/cm and the charge-to-breakdown is larger than 10 C/cm2under a constant stress current density of 0.1 A/cm2. The same high-density plasma system has also been applied for the direct nitridation of silicon surface using Ar/N2 or Ar/N,/H, gas ambient. The electrical properties of the silicon nitride are excellent enough to extend scaling limit of thermally grown silicon oxide. An advanced gas distribution system consisting of a newly-developed vaporizer, a flow control system, an electrically controlled valve and an advanced gas pumping system can control various source gas concentrations in the process chamber very accurately from the first atomic layer deposition. The newly-developed plasma and advanced gas distribution systems are suitable for the formation of high dielectric constant and ferroelectric films for ULSI in the 21st Century.
Ultrathin Tantalum Pent-Oxide Films for Ulsi Gate Dielectrics
Authors: Nishioka Yasushiro
Published: April 2011

Ultrathin tantalum pent-oxide (Ta2O5) films with a high dielectric constant over 20 and which are thinner than 10 nm have been extensively studied to realize small area capacitors for memories and high performance MOSFETs. The author and his colleagues started working on ultrathin Ta2O5 films with an equivalent oxide film thickness less than 4 nm for small capacitors for bipolar memories and DRAMS in 1984, and investigated extensively the effects of dry oxygen annealing of sputter-deposited thin Ta2O5 films on Si. We found that there was a process window (dry O2, 800 °C) where defects causing initial and latent breakdown were significantly reduced and where at the same time the reduction in the capacitance inevitably caused by the growth of interfacial SiO2 is kept small. This dry O2 annealing has been widely used for many years due to its effectiveness. This treatment was called “weak spot oxidation.” The interfacial SiO2, with a smaller dielectric constant of 3.9, underneath the Ta2O5 films causes a reduction of the capacitance and an increase of the equivalent film thickness. Annealing of the films after deposition and suppression of the interfacial SiO2 growth are the keys to realizing high performance and reliable Ta2O5 capacitors and gate insulators. In this paper, these fundamental processes are described, along with more recent developments of Ta2O5 thin film technologies, and the potential of the Ta2O5 films as an alternative for a future ULSI gate insulator are also discussed.
Ultrathin TiO2 Gate Dielectric Formation by Annealing of Sputtered Ti on Nitrogen Passivated Si Substrates in Nitric Oxide Ambient
Authors: Luan H. F. , Mao A. Y. , Lee S. J. , Luo T. Y. , Kwong D. L.
Published: April 2011

We have fabricated very thin TiO2 film (Teq∼20Å) by RTP oxidation of sputtered Ti in NO ambient on nitrogen passivated Si substrates. The leakage current is about two orders magnitude lower than SiO2 of identical Teq. Results show that NO passivation layer prior to sputtering is critical in reducing the leakage current. XPS results show that the temperature RTP NO oxidation of sputtered Ti is very important for achieving high quality TiO2 films. high oxidation temperature an SiO2 layer is formed at the interface between TiO2 and Si and the leakage current is approaching to that of SiO2.
Ultrathin Silicon Oxide and Nitride – Silicon Interface States
Authors: Brillson L.J. , Young A.P. , Schäfer J. , Niimi H. , Lucovsky G.
Published: April 2011

Local electronic states at nanometer-thick silicon oxide and nitride films on Si can be studied on an unprecedented scale using low - energy cathodoluminescence spectroscopy to observe optical transitions of defect bonding arrangements at ultrathin film interfaces prepared by low -temperature plasma deposition. Our results illustrate significant differences in the dependence of specific defects at the oxide versus nitride interfaces on thermal annealing and hydrogenation.
JVD Silicon Nitride and Titanium Oxide as Advanced Gate Dielectrics
Authors: Ma T.P.
Published: April 2011

The principle and practice of the Jet-Vapor Deposition (JVD) technique for thin-film deposition will be introduced, followed by a presentation of the properties of ultra-thin JVD silicon nitride (designated SiN in this paper) as advanced MOS gate dielectric. Recent results on the JVD TiO2/SiN gate stack will also be presented
Interfacial Properties of Si-Si3N4formed by Remote Plasma Enhanced Chemical Vapor Deposition
Authors: Misra V. , Lazar H. , Kulkami M. , Wang Z. , Lucovsky G. , Hauser J.R.
Published: April 2011

This paper presents results on the interfacial properties of Si3N4on NMOSFETs and PMOSFETs. Silicon nitride, formed by remote plasma enhanced chemical vapor deposition, was found to display severely degraded interfacial properties, in which the PMOS interfaces were significantly more degraded than NMOS interfaces. This is believed to be indicative of a relatively high density of interface traps located below the Si mid-gap that inhibit hole channel formation. These traps are believed to originate from the intrinsic nature of Si- Si3N4interface. Bonding constraint theory was applied to conclude that the Si-Si3N4interface is over-constrained compared to the Si-SiO2interface and consequently results in a higher intrinsic defectivity. A systematic study of the oxygen and hydrogen content in the silicon nitride film and its effect on electrical properties is also presented. Based on the electrical results it is concluded that the presence of oxygen either as a) a monolayer at the interface or b) within the silicon nitride film can produce high quality interfaces suitable for aggressively scaled CMOS devices.
Arsenic Trapping and its Effect on Enhanced Diffusion
Authors: Brindos Richard , Law Mark E. , Jones Kevin S. , Andideh Ebrahim
Published: April 2011

CVD grown boron marker layers were used to monitor the release of silicon interstitials from an arsenic doped surface region that was subsequently implanted with silicon. These structures were annealed for various times at 750°C in a nitrogen ambient. A comparison of boron spike enhancement and defect dissolution is made. It is shown that enhancement values from the Si+ implant were reduced at short times for samples containing arsenic compared to samples implanted with Si+ alone or As− alone. The TEM results showed that defect densities were dramatically reduced for the samples containing As. These results imply that the previously reported reduction in {311} formation observed in As doped wells is most likely not a Fermi level effect and is consistent with the formation of As interstitial clusters (AsIC's). The data shows that AsIC's form and control extended defect formation and slow the enhanced diffusion.
Micromechanical Thin-Film Characterization
Authors: Scherge M. , Mollenhauer O. , Spiller F. , Schaefer J. A.
Published: April 2011

Microelectromechanical systems (MEMS) can be regarded as advanced film-based devices. Although the dimensions of a MEMS are in the range of micrometers to millimeters, due to low mass and contact area the interaction of the micro parts is confined to the upper monolayers of the material. To achieve a good performance as well as a long lifetime it is necessary to control the adsorbate coverage of the micro parts. Besides the tools of surface science (XPS, HREELS, AES, … ) a precise characterization of the adsorbate film with respect to mechanical properties (adhesion, friction, mechanically induced desorption) is required. Those needs are met with a new generation of test equipment comprising of sensors and actuators, thus, rendering the instruments also a MEMS. Force sensing devices made of glass are introduced to measure ultra low deflections caused by the interaction of the micro parts via the adsorbate layer. The devices combine precisely etched glass structures (bending beams,) with fiber optics.
Autobiography
Authors: Turnbull David
Published: April 2011

I was born and reared on a family farm in northwest Illinois and obtained my elementary education in a single-teacher village school. Apparently I had a mild case of dyslexia, for I was virtually unable to read until I had been in school for more than two years. Then, through the valiant tutelage of my mother, who had been a school teacher, I suddenly became able to read and ever afterward did so, well and extensively. Our farming community was not included in any secondary school district, and my parents managed to have me admitted to Kewanee High School which, at the time, was considered to be the most outstanding school, academically, in the area. There, indeed, I received an excellent education from an outstanding group of teachers. I was especially inspired by the Misses Minnie Trask and Wildred Ewan, who posed demanding intellectual challenges and encouraged imaginative but rigorous modes of thought. It seemed that I learned most from having to solve difficult problems and rather little from classroom exposition, however excellent it was. Because of this, the emphasis of my own teaching has been on the posing of meaningful and challenging problems. In this, I have tried to follow the dictum, attributed to Galileo, “you can't teach a person anything, you can only help them to find it within themself”.
Statistical Aspects of Martensitic Nucleation
Authors: Olson G. B. , Tsuzaki K. , Cohen Morris
Published: April 2011

Analysis of the Cech-Turnbull small-particle martensitic transformation experiments in terms of heterogeneous nucleation theory defines an exponential nucleation-site potency distribution. Sensitive acoustic-emission detection of martensitic nucleation events shows that the same form of distribution describes the behavior of bulk polycrystals, and the influence of heat treatment on the distribution amplitude can be identified in this way. On the assumption of a random distribution of pre-existing nucleation-site orientations, the effect of applied stress on the effective potency distribution has been calculated, thus accounting for an observed nonlinear stress dependence of the transformation kinetics. The model also predicts a transformation “yield locus” for multiaxial stress.
Anomalous Behavior of Peak Resistance Temperature for low x in As-Deposited La1-xCaxMnO3 Films on NdGao3 and SrTiO3 Substrates
Authors: Broussard P. R. , Cestone V. C.
Published: April 2011

We have grown thin films of La1-xCaxMnO3 using off-axis cosputtering for x ≤ 1/3 onto (001) NdGaO3 and (100) SrTiO3 substrates from individual targets of LaMnO3 and La2/3Ca1/3MnO3. As-deposited films of La2/3Ca1/3MnO3 on NdGaO3 have a peak resistance temperature of ≈ 260 K. We see a difference in the peak temperature between the two types of substrates of ≈ 15 K, with samples on NdGaO3 having higher peak temperatures. As the value of x is reduced from 1/3, the peak resistance temperature decreases until x ≈ 0.15, when the peak temperature has an upturn. Even down to x=0 we still observe a metal-insulator transition (at 185 K) for films on NdGaO3, while samples on SrTiO3 show only activated behavior. We also find a scaling relationship between the peak temperature and the resistivity activation energy of the films.
Silicon-Oxynitride (SiON) for Photonic Integrated Circuits
Authors: Salemink H. W. M. , Horst F. , Germann R. , Offrein B. J. , Bona G. L.
Published: April 2011

We report on the fabrication and analysis of silicon-oxynitride (SiON) as core material for silicon-based planar photonic waveguide circuits. Features of devices made of this particular SiON material are: (1) a silicon-compatible technology (low-cost perspective), (2) a waveguide structure with high dielectric index contrast, allowing a very compact device layout (approximately 10× smaller radius of curvature than conventional doped SiO2 technology), (3) a low optical loss < 0.15 dB/cm, in the 1550 nm telecommunication window and (4) a negligible polarization dependence. The materials aspects and resulting analyses of the SiON layers as well as particular device properties are described.
Barium Titanate Ceramic/Ceramic 0–3 Composites for Ultrasonic Transducer Applications
Authors: Cheung M. C. , Chan H. L. W. , Zhou Q. F. , Choy C. L.
Published: April 2011

Barium titanate (BaTiO3) 0–3 ceramic/ceramic composite thick films (∼16μm) for ultrasonic transducer applications were fabricated by a modified sol-gel process. Nano-sized BaTiO3 powder was dispersed in a sol-gel matrix of BaTiO3 to form a 0–3 composite solution. Films were prepared by spin coating and then annealed at various temperatures. The crystallization of the composite film was studied by X-ray diffraction. The dielectric permittivity and the ferroelectric properties of the film were also measured.
Time-Dependent Exciton Correlations in Nanoscale Quantum Dot
Authors: Jönsson Lars , Sakhel Roger , Wilkins John W.
Published: April 2011

In nanoscale quantum dots, subpicosecond laser pulses can induce and probe strong time-dependent Coulomb correlations between confined electrons and holes. Correlation dynamics for one or two electron-hole pairs driven by both interband and intraband lasers can be simulated by numerical solution of the time-dependent Schrddinger equation within a configuration-interaction description. For example, Coulomb correlations of two electrons and two light holes in a 5×25×25 nm3 GaAs quantum dot yield strong oscillations in the luminescence. Pure correlation effects are revealed by a carefully chosen sequence of three circularly polarized subpicosecond laser pulses. For this case, the Coulomb and electron-laser matrix elements were calculated within the effective-mass approximation with infinite potential walls. For a quantum dot with an internal tunneling barrier that splits the energy levels on the 10 meV scale, correlation effects couple the interband and intraband optical response. Work in progress aims at more realistic geometries, finite outer potential walls, and better description of the band structure, using real-space methods, multi-band models, and tight-binding Hamiltonians. With the help of 'dynamic state selection,' simulation times can be reduced by a factor of 5–10. Dynamic state selection allows the computer, by generic selection criteria, to use only those determinants that are momentarily most important. This approach is especially useful in multi-pulse simulations where the coupled determinants belong to different classes at different times.
An Ivestigation of Temperature-Manipulated Size and Shape Evolution of Preformed Core-Shell Nanoparticles
Authors: Maye M.M. , Zheng W.X. , Leibowitz F.L. , Ly N.K. , Eichelberger H.H. , Zhong C.J.
Published: April 2011

This paper presents a study of heating-induced size and shape change for pre-synthesized composite nanoparticles of ∼2 nm gold cores encapsulated with alkanethiolate monolayers. The results have demonstrated an evolution in size and shape of the nanoparticles towards monodispersed larger core sizes with well-defined and highly-faceted morphologies. The evolved particles were encapsulated with the thiolate shells. The morphological and structural evolutions were characterized using TEM, XRD, UV-Vis and FTIR spectroscopy. While temperature-driven crystal growth is known for non-encapsulated particles, the evolution of the thiolate-encapsulated nanoparticles in solutions into well-defined morphologies represents an intriguing example of temperature manipulations of nanoparticle monodispersity and shape.
Coarse Grained Free Energy Functional for Lennard-Jones Systems
Authors: Gracheva M. E. , Rickman J. M. , Gunton J. D. , Coffey D. C.
Published: April 2011

Results are presented for the coarse grained distribution function and Ginzburg-Landau free energy function for coexistence of liquid and gas phases. These distribution functions were obtained by two different methods: 1) the compilation of particle density information from different coarse-grained cells using the canonical ensemble, and 2) the compilation of energy and density information from a single simulation cell by tuning the chemical potential using the grand-canonical ensemble. Both methods permit the calculation of a coarse-grained free energy functional which links the atomic and mesoscopic length scales.
Use of the Vacuum Arc Discharge for the Surface Modification
Authors: Kovalenko Vladimir A.
Published: April 2011

Steel surface saturation by nitrogen (nitriding) results in a high increase in surface hardness and a decrease in friction rate. This treatment is widely used to increase the lifetime of cutting tools and wearing parts in machines.

A new approach of steel surface treatment by using the vacuum arc discharge in nitrogen is presented. The apparatus uses two arc vacuum discharges. The first discharge is a metal vapor discharge and serves for both the cleaning- heating of the treated surface and for the initiation of the second vacuum arc discharge in nitrogen. The vacuum arc source of metallic plasma allows us the simultaneous implantation of desirable metals and surface saturation by nitrogen. The developed arc vacuum discharge method shortens the nitriding time 2 to 3 times in comparison to the glow discharge technology. The suggested method of the surface treatment is suitable for a wide variety of steels. The hardness measurement results of nitriding and combined chromium with nitriding treatments of several steel samples are presented and discussed.
ECR Plasma Oxidation: Dependence on Energy of Argon Ion
Authors: Matsuo S. , Yamamoto M. , Sadoh T. , Tsurushima T. , Gao D. W. , Furukawa K. , Nakashima H.
Published: April 2011

Effects of ion-irradiation on oxidation of silicon at low temperatures (130°C) in an argon and oxygen mixed plasma excited by electron cyclotron resonance (ECR) interaction are investigated. First, dependence of energy and flux of incident ions on the flow rate and the microwave power is evaluated. It is shown that the flow rate and the microwave power are key parameters for controlling the energy and the flux of incident ions, respectively. Second, growth kinetics of the oxide films are studied. The growth rate depends on the energy and the flux of argon ions irradiated to the substrate, and the growth thickness increases proportionally to the root square of the oxidation time. Thus, the growth rate is limited by diffusion of oxidants enhanced by irradiation with argon ions. The effect of substrate bias on oxidation characteristics is also discussed. The electrical properties of the oxide films are improved by increasing the bias. The improvement is due to the reduction of damage at the surface of the substrate induced by the irradiation.
Layer Splitting by H-Ion Implantation in Silicon: Lower Limit on Layer Thickness?
Authors: Qian C. , Terreault B.
Published: April 2011

The Smart-Cut™ process and its variants involve H and/or He ion implantation and annealing to neatly exfoliate a layer of material as thin as the ion range. At low ion energy, as required for further miniaturisation, several effects may inhibit the process. We implanted undoped Si (100), (110) and (111) with 5 keV H or D ions at doses below (3–4×1016/cm2) or above (5.5×1016/cm2) the critical dose for blistering. The samples were either isochronally annealed for 1h or 2h in three steps at 500, 550 and 600°C, or subjected to thermal desorption spectroscopy (TDS) with linear ramps of 7.5 K/min up to 500, 550 or 600°C. The surface morphology was observed at each step by scanning electron or atomic force microscopy. Below the critical blistering dose, TDS only shows a broad high temperature (∼525°C) peak, while above that dose, a low temperature peak (∼360°C) also appears, though weakly in the case of (110) samples. The exfoliated area (as % of total surface) increases with temperature, and also varies with wafer orientation, being minimum for (110) samples and maximum for (111) samples. This orientation effect is much more pronounced for H-implants than for D-implants. All these trends indicate that ion channelling leads to an inhibition of exfoliation.
Growth of Metal Nucleus on Polyimide Surface with Photochemical Reaction
Authors: Tomita M. , Murahara M.
Published: April 2011

Circuit patterned nucleation of copper or nickel atoms onto polyimide surface was demonstrated by using ArF excimer laser (λ=193nm) and copper sulfate aqueous solution (CuSO4.5H2O+nH2O), or nickel sulfate aqueous solution (NiSO4–6H2O+nH2O) in an atmospheric pressure. Photo-excited C-H bonds of the polyimide surface were effectively dehydrated with hydrogen atoms which were photodissociated from the water. The dangling bonds of the dehydrated hydrogen atoms were combined with the oxygen and the copper or nickel atoms that were photodissociated by CuSO4 solution or NiSO4 solution. Thus, C-O-Cu bonds or C-O-Ni bonds were formed on the surface. After this copper and nickel substitution, it was carried out onto the nucleated parts by usual electroless plating at 70 °C. In this process, the conductive circuit patterned copper or nickel thin film was deposited on polyimide surface.
Etching and Surface Smoothing with Gas-Cluster Ion Beams
Authors: Fenner D. B. , Torti R. P. , Allen L. P. , Toyoda N. , Kirkpatrick A. R. , Greer J. A. , Difilippo V. , Hautala J.
Published: April 2011

Surface processing of microelectronic materials by bombardment with nanoparticles of condensed gases (i.e., clusters) in the form of an ion beam, makes possible etching and smoothing of those surfaces to very high figures of merit. As this is not possible with any conventional ion method, gas-cluster ion-beam systems have great potential in manufacturing. The formation of gas clusters and their collision with surfaces provides an interesting arena for novel physics and surface science. This paper outlines a physical model for the clusters and surface interactions, and provides examples of surface processing. In particular, the reduction of surface roughness while etching by cluster-ion bombardment is illustrated for various materials utilized in microelectronics.