bluuebunny/crossref_metadata_2025 huggingface dataset:
InGaAs/GaAs Strained-Layer QW Vertical Cavity Surface Emitting Laser Structures grown on GaAs (311)A Substrates by MBE
Authors: Takahashi M. , Vaccaro P. , Fujita K. , Watanabe T.
Published: April 2011

We report the crystal growth conditions and lasing characteristics of InGaAs-GaAs strained-layer quantum well vertical cavity surface emitting lasers (VCSELs) grown on GaAs(311)A substrates by molecular beam epitaxy. A significantly smooth surface and high reflectivity of more than 99 % were achieved. Very flat and dislocation-free AlAs/GaAs hetero-interfaces were obtained. Furthermore, a very low threshold of 5.5 mA and current density of 270 A/cm2 have been achieved for the first time under CW operation at room temperature. In addition, we demonstrate stable polarization characteristics at high currents. These results are believed to be a consequence of both the predicted high gain and anisotropic gain distribution on the (311) surface.
Stable Visible Photoluminescence from Annealed Polysiloxene-Based Thin Films
Authors: Miyazaki S. , Mouraguchi A. , Shinohara M.
Published: April 2011

Polysiloxene-based films have been prepared by plasma enhanced CVD in a Si2H6+O2 gas mixture at a substrate temperature of −110°C and annealed at temperatures from 700°C to 1000°C. It is found that the film annealed at 1000°C is composed of 1∼5nm Si crystallites embedded in SiO2 and exhibits stable, intense visible-luminescence at room temperature under 488nm excitation. The temperature and excitation power dependences of the steady-state and timeresolved luminescence of the annealed films suggest the radiative recombination through localized states in the Si/SiO2 interface region.
Post Epitaxial Disordering of CuPtB Ordered AIGaInP/GaInP for Microstructuring
Authors: Bukard M. , Englert A. , Geng C. , Scholz F. , Schweizer H.
Published: April 2011

Lateral order/disorder structures have been fabricated out of ordered GaInP quantum wells by ion implantation.

Using high resolution electron beam lithography for definition of implantation masks, we achieve wire structures down to 35nm width. Implantation was carried out at energies down to 25keV and doses from 3e10cm−2 to 6e13cm−2. The so created vacancies lead to a reduction of the disordering temperature threshold of about 850°C for mere thermal disordering. Annealing those structures at 800°C results in selective disordering in the unmasked regions. We have ordered wire structures within disordered barriers. Even for the smallest mask widths of 35nm, the PL emission of wires and barriers are well resolved.
Cu Films on Si(100) by Partially Ionized Beam Deposition
Authors: Koh Seok-Keun , Kim Ki-Hwan , Han Sung , Jang Hong Gui , Jung Hyung-Jin
Published: April 2011

Highly (111) oriented Cu films with a thickness around 1800 Å were prepared on Si (100) at room temperature by partialy ionized beam deposition (PIBD) at pressure of 8 × 10-7 - 1 × 10-6 torr. Effects of acceleration voltage (Va) between 0 and 4 kV on such properties as crystallinity, surface roughness, resistivity, etc. of the films have been investigated. The Cu films deposited by PIBD had only (111) and (200) planes and the relative intensity ratio, 1(111)/I(200), of the films increased from 6.8 at Va=0 kV to 37 at Va=4 kV. There was no indication of impurities in the system from AES analyses. A large increase in grain size of the films occurred with Va up to Va– 1 kV, but little increase occurred with Va>lkV. Surface roughness of the films at the ionization potential of 400 V decreased with Va, and resisivity had the same trends as that of the surface roughness. In the Cu films made by PIBD, it appears that changes of resistivity are mainly due to a surface scattering rather than a grain boundary scattering. The via holes, which is of 0.5. μm diameter x 1.5 μm deep, in the Cu films made at Va=4 kV, were completely filled without voids. Adhesion of the Cu film on Si(100) deposited at Va=3 kV was 5 times greater than that of Cu film deposited at Va=0 kV, as determined by a scratch test.
Integration of Al-Fill Processes for Contacts and VIAS
Authors: Barth H. J.
Published: April 2011

Today different Al-fill techniques are used for the fill of submicron contacts and vias. The integration aspects of the most promising approaches, Al-reflow, cold/hot Al-planarization and high pressure Al-fill (Forcefill) are compared to the widely used W-plug technique. The filling properties are discussed with respect to future applications in ULSI devices. Special attention is given to the barrier stability in contacts and the influence on patterning. Various electrical data and reliability results are compared to metallizations with W-plugs. The implications of the Al-fill processes on chip design, especially on the size and shape of holes, the pattern density, the possibility of producing stacked contacts/vias and the metal to contact/via overlap are considered also. In an outlook for future developments, e.g. the introduction of low k dielectrics, the inverse metallization architecture with (dual) damascene interconnects and the emerging Cu metallizations, Alfill processes are facing new challenges which will be discussed.
Gas Cluster Ion Beam Processing for ULSI Fabrication
Authors: Yamada I. , Matsuo J.
Published: April 2011

Unique characteristics of gas cluster ion beam bombardment are discussed in terms of ULSI fabrication processes. Cluster ion beams consisting of a few hundreds to thousands of atoms have been generated from various kinds of gas materials. Multi-collisions during the impact of accelerated cluster ions upon the substrate surfaces produce fundamentally low energy bombarding effects in a range of a few eV to hundreds of eV per atom at very high density. These bombarding characteristics can be applied to shallow ion implantation, high yield sputtering and smoothing, surface cleaning and low temperature thin film formation.
Chemical Vapor Deposition of Al Films From Dimethylethylamine Alane on GaAs(100)2×4 Surfaces
Authors: Karpov I. , Campbell J. , Gladfelter W. , Franciosi A.
Published: April 2011

Chemical vapor deposition (CVD) of Al from dimethylethylamnine alane on atomically clean GaAs(100)2×4 surfaces has been investigated using an ultra-high-vacuum CVD reactor. Film composition, microstructure and growth rate were examined for deposition temperatures in the 100-500°C range. The results indicate reduced impurity incorporation at the lower deposition tenmperatures, and growth rates that are relatively temperatureindependent in the low-pressure regime examined (10−4to 10−5Torr). At temperatures ≥400°C the microstructure of films deposited by CVD and evaporation is remarkably similar, but at the lower deposition temperatures (∼150°C) the specific chemistry of the CVD process affects the film texture and preferential orientation.
Low Temperature Deposition of Tacn Films Using Pentakis(Diethylamido)Tantalum
Authors: Jun Gyu-Chang , Cho Sung-Lae , Kim Ki-Bum , Shin Hyun-Koock , Kim Do-Heyoung
Published: April 2011

TaCN films were deposited at low temperature (≤400 °C) by metallorganic chemical vapor deposition (MOCVD) using pentakis(diethylamido)tantalum (PDEAT) as a precursor. The activation energy of the surface reaction is about 0.79 eV and the maximum deposition rate is about 100 Å/min at 350 °C. The resistivity of the as-deposited film decreases as the deposition temperature increases and the minimum value of resistivity obtained is 6000 μΩ-cm for the sample deposited at 400 °C. Major chemical elements in the films were detected as Ta, C, and N with some amounts of O by Auger electron spectroscopy (AES). By x-ray photoelectron spectroscopy (XPS), it is identified that the most of carbon in the films was bonded to Ta. The microstructural investigation using high resolution transmission electron microscopy reveals a nanocrystalline phase with an average grain size of about 30 Å. Preliminary investigation of the diffusion barrier property for copper showed that the 300 Å of TaCN diffusion barrier was failed after annealing at 500°C for 1 hr.
Ptfe Nanoemulsions as Spin-On, Low Dielectric Constant Materials For Ulsi Applications
Authors: Rosenmayer Tom , Wu Huey
Published: April 2011

ULSI Interconnects require insulative materials with as low a dielectric constant as possible in order to minimize crosstalk and parasitic capacitance. Transmission line simulations indicate that crosstalk in parallel interconnect lines can be dramatically reduced by lowering the dielectric constant of the insulation from 4 to 2. Polytetrafluoroethylene (PTFE) has a desirably low dielectric constant (2.05), but has previously been difficult to deposit in thin films suitable for integrated circuit applications. PTFE has other desirable properties, including temperature resistance in excess of 400 C and outstanding chemical resistance.

A novel liquid material has been developed which permits the spin coat deposition of full density PTFE films from 0.2 to 1.0 microns thick. The deposition liquid is a solvent-free, stable PTFE nanoemulsion consisting of fully cured < 0.05 micron particles, surfactant, and water. The nanoemulsion is an equilibrium phase which is thermodynamically stable, optically clear, and has low viscosity. These properties are achieved because of the unusually small particle size of the nanoemulsion. The films are uniform in thickness with a standard deviation of < 2% and edge-to-center variation of < 5%. The films have a weight loss rate of less than 0.008%/min at 425 ° C. Good adhesion to Al, Si3N4, Si, and SiO2 is obtained when the films are evaluated per ASTM D3359-93. Several reseachers have reported methods by which various materials may be deposited onto PTFE with acceptable results.
Synthesis of Periodic Mesoporous Silica Thin Films
Authors: Anderson M. T. , Martin J. E. , Odinek J. G. , Newcomer P.
Published: April 2011

We have synthesized periodic mesoporous silica thin films (PMSTF) from homogeneous solutions. To synthesize the films a thin layer of a pH = 7 micellar coating solution that contains TMOS is dip- or spin-coated onto silicon wafers, borosilicate glass, or quartz substrates. Ammonia gas is diffused into the solution and causes rapid hydrolysis and condensation of the TMOS and the formation of periodic mesoporous thin films within ∼10 seconds. The combination of homogeneous solutions and rapid product formation maximizes the concentration of desired product and provides a controlled, predictable microstructure. The films have been made continuous and crack-free by optimizing initial silica concentration and film thickness.
Designer Carbons Templated by Pillared Clays: Lithium Secondary Battery Anodes
Authors: Sandí G. , Carrado K. A. , Winans R. E. , Brenner J. R. , Zajac G. W.
Published: April 2011

This work describes the designed synthesis and physical characterization of carbons containing predictable microporosity. The approach is to pyrolyze aromatic hydrocarbons such as pyrene within a pillared clay. The pillared clay serves two functions. It performs as the inorganic template around which the designer carbon can be formed, and it acts as an acid catalyst to promote condensation of the aromatics similar to the Schöll reaction. These precursors then undergo thermal polymerization and carbonization at 700 °C. Removal of the pillared clay template is accomplished by standard acid demineralization techniques, leaving behind carbons with 15 to 50 Å holes.
Bicontinuous Cubic Phase as a Matrix for the Synthesis of Semiconductor Nanocrystallites
Authors: Yang Jianping , Qadri Syed , Ratna Banahalli
Published: April 2011

Bicontinuous cubic phase of lipid has been utilized for the first time as a matrix to synthesize II–VI (CdS) and IV–VI (PbS) semiconductor nanocrystallites. The nanoparticles were isolated from the lipid matrix and stabilized by capping with a thiol compound before purification. Two different sizes (2.3 nm and 3.0 nm) of CdS particles were prepared by varying the conditions of preparation. The size was determined by a combination of UV-vis absorption spectra and X-ray diffraction (XRD). The steep absorption edges of the two CdS samples indicate very narrow size distribution. XRD and transmission electron microscopic imaging of PbS nanocrystallites revealed that the size was 4.9 nm with nearly monodispersed size distribution.
Permeability and Structure of Resorcinol – Formaldehyde Gels
Authors: Scherer G. W. , Alviso C. , Pekala R. , Gross J.
Published: April 2011

The permeability (D) of resorcinol-formaldehyde (RF) gels was measured using a beam-bending technique. For gels made at various solids contents and with different catalyst contents, the permeabilities ranged over a factor of ∼50; the pore radii inferred from D varied from ∼3 to 30 nm. Pore radii obtained on RF aerogels using nitrogen desorption were severely affected by compression of the aerogel by capillary forces (resulting from the surface tension of liquid nitrogen). After correction for that effect, the desorption data were found to be in very good agreement with the pore sizes calculated from D.
Heterogeneous Microcomposite Materials Based on Porous Matrices and Liquid Crystals
Authors: Aliev F. M. , Sinha G. P.
Published: April 2011

Heterogeneous microcomposite materials based on porous matrices with randomly oriented, interconnected pores (porous glasses with average pore sizes of 100 Å and 1000 Å) and parallel cylindrical pores (Anopore membranes with pore diameters of 200 Å and 2000 Å) impregnated with liquid crystals (LC) were investigated by dynamic light scattering and dielectric spectroscopy. The physical properties of confined LC are very different from that of the bulk. One of the new properties among others observed for LC confined in porous matrices is the slow relaxational process which does not exist in the bulk LC and a wide spectrum of relaxation times (10−8 – 10)s which were established in both dynamic light scattering and dielectric experiments. We found that for LC dispersed in porous matrices with randomly distributed interconnected pores, the contribution to physical properties and observed behavior from interfacial layers dominates and almost completely determines low frequency relaxational process.
Aluminas Rehydration and Dehydration
Authors: Fripiat J. J.
Published: April 2011

In this review paper, results on the A12O3-water interactions will be critically examined. The synthesis of alumina precursors rich in structural defects can be operated in an aqueous solution containing ligands with high affinity for A13+aqor by restricted hydrolysis of Al-alkoxides. Calcination of the gels yields transition aluminas containing four (IV), five (V) and six (VI) fold coordinated aluminum. The pore-size distribution, the Alvcontent and the degree of crystallinity are controlled by the degree of condensation of the oligomer species in the gel. In a dehydrated alumina two kinds of AlIVwith isotropic chemical shifts at ∼73 and 58 ppm, respectively, are present. The distorted AlIV(chemical shift at 58 ppm) and Alvare surface species. Upon water chemisorption the distorted AlIVline disappears while the Alvline is reinforced. As bulk rehydration progresses the Alvline intensity decreases. It is only partially restored upon recalcination. Thus, hydration-rehydration cycles cure the solid from its defects and increase crystallinity. The onset of rehydration is the chemisorption of water on the surface Lewis sites just as Lewis sites result from a thorough dehydration.
Selective Dissolution in Copper-Tin Alloys: Formation of Corrosion-Resistant Patina on Ancient Chinese Bronze Mirrors
Authors: Taube Michelle , Davenport Alison J. , King Alexander H. , Chase W. Thomas
Published: April 2011

Many ancient Chinese bronze mirrors have survived with a patina that leaves the delicate relief surface decorations intact. The microstructure of these ancient mirrors is two-phase and consists of acicular α-phase (Cu-rich) regions encased in a δ-phase (Sn-rich) matrix. At the surface, there is evidence of selective dissolution of the α-phase; the α-phase regions are replaced pseudomorphically by a mineral product with the δ -phase remaining metallic. Electrochemical polarization has been used to drive the copper dealloying process in modern, cast bronze. Synchrotron x-ray diffraction was employed to compare the ancient samples with those that were prepared potentiostatically. Poorly crystallized tin oxide (SnO2) was found in the α - replacement products of both sample types. The corrosion-resistance of the potentiostatically-treated bronze samples was tested by atmospheric exposure. Comparison with exposed, untreated samples indicated that the treatment was protective.
Mineral Redox Buffers and The Stability of Organic Compounds Under Hydrothermal Conditions
Authors: Seewald J. S.
Published: April 2011

Organic compounds play an integral role in numerous geochemical process in subsurface environments. To evaluate factors that regulate the stability of ethane, ethene, propane, and propene in hydrothermal systems a series of experiments were conducted at 300 to 325°C and 350 bars. The experiments contained the mineral assemblages pyrite-pyrrhotite-magnetite, hematite-magnetite-pyrite, and hematite-magnetite to buffer fO2, aH2(aq) and aH2S(aq) at geologically reasonable values.

Results of the experiments suggest that under appropriate physical and chemical conditions, metastable redox dependent thermodynamic equilibrium involving liquid water and inorganic iron-bearing mineral assemblages may regulate the relative abundance of short chain alkanes and their corresponding alkenes. In addition, alkenes represent an important intermediary in the conversion of n-alkanes to methane and oxidized species such as carbon dioxide, ketones alcohols, and organic acids.

The rates of redox dependent organic reactions during the experiments were strongly influenced by the presence of sulfur. Under relatively oxidizing conditions greater catalytic activity due to the presence of dissolved sulfur species was observed. Fluid speciation calculations suggest that oxidized aquous sulfur compounds represent the catalytically active species.

These results suggest that redox conditions and the presence or absence of dissolved sulfur species in natural sedimentary environments may strongly influence the stability of hydrocarbons. Accordingly, models used to predict the stability of oil and the formations of natural gas need to account for chemical processes that involve both organic and inorganic sedimentary components.
Large area Pulsed Laser Deposition of Aurivillius-Type Layered Perovskite Thin Films
Authors: Pignolet A. , Curran C. , Welke S. , Senz S. , Alexe M. , Hesse D. , Gösele U.
Published: April 2011

Thin films of Aurivillius-type layered perovskites of Bi4Ti3O12and SrBi2Ta2O9have been epitaxially deposited by pulsed laser deposition (PLD) on SrTiO3single crystal substrates. Bi4Ti3O12has been deposited as well on a CeO2JYSZ/Si(100) buffer layer, and on Pt-coated oxidized silicon for electrical measurements. Using a new technique for large area PLD, Bi4Ti3O12has also been deposited on a whole (100)-oriented 3”- Si wafer. The obtained films have a uniform thickness over a diameter greater than 50 mm, corresponding to an area of about 20 cm2. It is likely that homogeneous deposition on entire wafers of 3-inch in diameter will be accomplished in the near future. The composition, structure, and electrical properties of the films are presented.
Dependence of Composition and Microstructure of RuOx Films on Target Status and Substrate Temperature in Reactive Sputtering Deposition
Authors: Wang Q. , Yang K.-A. , Franciosi A. , Evans D. F. , Gladfelter W. L.
Published: April 2011

Ruthenium oxide films were deposited on Al2O3 (0001) and (1102) substrates using reactive sputtering under two different target surface conditions. Films grown when the surface of the target was metallic ruthenium (metallic-target) showed a Ru: O ratio of 1: 2.0±0.05 as determined by Rutherford backscattering spectrometry. At elevated deposition temperatures, these films aligned with the substrates as RuO2 (100) ║ A12O3 (0001) and RuO2 (101) ║ Al2O3(1102). Films deposited when the target surface was fully oxidized (oxidized-target) exhibited a Ru: O ratio of 1: 2.5±0.05 and displayed an oriented crystalline structure even at room temperature. The resistivity of the RuO2.5 films was 75 μΩ-cm and was independent of temperature between 5 and 300 K. Possible causes of this behavior are discussed.
Effect of Surface Morphology of NiCr-Bottom Electrode on Preparation of Ferroelectric PZT Thin Film Capacitor
Authors: Lee K.B. , Rhee B.R. , Cho S.K.
Published: April 2011

We have studied the optimum conditions of the deposition of NiCr-bottom electrode for preparing the ferroelectric PZT(50/50) thin film capacitor. The NiCr(80/20) layer of about 300nm in thickness was deposited on bare Si(111) wafer by rf magnetron sputtering. The surface morphology and crystallinity were investigated by using Atomic force microscope (AFM) and X-ray diffractormeter (XRD). It is found that the size and crystallinity of grains of NiCr or Ni-silicide depend mainly on the rf power. The PZT(50/50) thin films were prepared on NiCr/Si substates by spin-casting of PZT coating sol and then annealing at 520°C in air for crystallization. The undesirable Pb-silicate is found to be grown during post-annealing in case that substrates having NiCr layer deposited by high power above 80 W are used. We suggest that the formation of Pb-silicate is due to the thermal diffusion of Pb or PbO through crystalline NiCr-grain boundaries. The ferroelectric PZT thin films having the perovskite structure can be obtained by using the NiCr-bottom electrodes whose morphologies are in the amorphous-crystalline boundaries, in which the surface roughness and grain size of NiCr layer is minimum. The values of the dielectric constant, εn, were measured in the range 300˜500, the remanent polarization, Pr, in the range 10˜13 C/cm2 and the coercive field, Ec, around 160 kV/cm, depending on the deposition conditions of NiCr layers.
Step Coverage of Pb(ZrTi)O3 Thin Films Grown by Mocvd
Authors: Shimizu M. , Hyodo S. , Fujisawa H. , Niu H. , Shiosaki T.
Published: April 2011

Step coverage of PZT grown by MOCVD was influenced by the growth temperature, the reaction pressure and the aspect ratio of the trench. PZT films grown on Si steps at growth temperatures ranging from 500 to 600°C and at reaction pressures ranging from 3 to 10Torr showed a step coverage of 52 to 86%. The step coverage of PZT grown at 600°C and at 5Torr – conditions which were suitable for the growth of perovskite phase – was 75%. The step coverage of Pt on Si and on SiO2 was 20% and 25%, respectively.
Study of Thin Film Ferroelectric Superlattices
Authors: Kim Y. , Erbil A. , Thomas E.W. , Kushwaha A. , Gerhardt R.
Published: April 2011

The study of ferroelectric thin films has evoked special interest owing to their numerous applications. In this study, epitaxial or highly oriented PbTiO3/PLT (Lead Titanate / La modified Lead Titanate) ferroelectric superlattice thin films were grown by the metalorganic chemical vapor deposition (MOCVD) technique. Compositional modulation by Secondary Ion Mass Spectroscopy (SIMS) established the nature of these films as desirable for high quality device applications. The thickness and the refractive index of each film was determined by using a prism coupler. The dielectric behavior of these films was studied as a function of frequency.
Structure, Composition and Properties of (Pb,La)TiO3 Thin Films by Rf Magnetron Sputtering
Authors: Murhy C.E. , Hata H. , Tsutsumi K.
Published: April 2011

Thin films of lanthanum-doped lead titanate for use in pyroelectric detectors were deposited on Si wafer system substrates by an RF magnetron sputtering method. Deposition was from a ceramic target with excess lead using Ar plus N2O sputter gases. The film structure, composition and electrical properties were examined as a function of substrate temperature during film deposition, Tsub, from 600°C to 750°C. Dense, featureless film cross-sections existed up to Tsub=625°C, while vertical columns, indicative of crystalline material, were present from Tsub=650°C upwards. At Tsub=600°C films were amorphous, but from Tsub=625°C upwards a highly crystalline perovskite phase was found. The tetragonality was very small, c/a˜1.006, indicating the existence of a pseudo-cubic structure. Compared to the idealized chemical formula, Pb1−xLaxTi1−x/4O3, films produced at Tsub<650°C or Tsub>700°C were Pb deficient, while only in the very narrow 650–700°C Tsub range was near-stoichiometry obtained, with a slight lack of Ti. The substrate temperature during deposition is apparently a critical factor in obtaining stoichiometric films. The La content with respect to Pb was 9.5% which would be expected to yield a reasonably tetragonal crystal structure in bulk material, however stress due to the substrate may account for this discrepancy. The relative permittivity, εr, showed a sharp transition from ˜50 at Tsub=600°C to 450–550 between 650°C and 750°C. This behaviour parallels both the microstructural and crystal lattice changes from amorphous to perovskite material. Even though on polycrystalline underlayers, pyroelectric activity, p, was measured on as-deposited films, the polarization being directed into the substrate and a peak of 1.2×10−4Cm−2K−1 appearing at Tsub=700°C. After DC thermal poling, at 100°C with 8V for 20min, p increased dramatically, with Tsub 700°C and 725°C films exhibiting p=2.0×10−4Cm−2K−1. The peak in the poled p value corresponded to the maximum found in the crystal tetragonality and agrees with increasing p as polarization increases from a cubic to tetragonal structure.
Dielectric and Ferroelectric Characterization of Sol-Gel Derived Ca-Doped PbTiO3 Thin Films
Authors: Teowee G. , McCarthy K.C. , Franke E.K. , Boulton J.M. , Alexander T.P. , Bukowski T.J. , Uhlmann D.R.
Published: April 2011

A series of sol-gel derived CaTiO3- PbTiO3 thin films ( i.e. Pb1−xCaxTiO3 with x = 0 − 1) was prepared on platinized Si substrates and fired to temperatures ranging from 550C to 650C. Multiple spincoating was performed to obtain films up to 0.5 μm thick with an intermediate firing of 400C between coatings. After the final crystallization firing, top Pt electrodes were sputtered to form monolithic capacitors. These capacitors were subjected to dielectric and ferroelectric characterization using an impedance analyzer and Radiant Technology RT66A Ferroelectric Test System. XRD was used to study the phase development and phase assembly of the fired films. All compositions were single perovskite phase after firing to 600C. The effects of Ca content on the crystallization behavior and ferroelectric properties are discussed.
Mechanical Behavior and Constitutive Modeling During High Temperature Deformation of Al Laminated Metal Composites
Authors: Grishaber R. B. , Mishra R. S. , Mukherjee A. K.
Published: April 2011

A constitutive model for deformation of a novel laminated metal composite (LMC) which is comprised of 21 alternating layers of Al 5182 alloy and Al 6090/SiC/25p metal matrix composite (MMC) has been proposed. The LMC as well as the constituent or neat structures have been deformed in uniaxial tension within a broad range of strain-rates (i.e. 10−5 to 100 s−1) and homologous temperatures (i.e. 0.8 ≥ 0.95 Tm). The results of these experiments have led to a thorough characterization of the mechanical behavior and a subsequent semiempirical constitutive rate equation for both the Al 5182 and Al 6090/SiC/25p when tested monolithically. These predictive relations have been coupled with a proposed model which takes into account the dynamic load sharing between the elastically stiffer and softer layers when loaded axially during isostrain deformation of the LMC. This model has led to the development of a constitutive relationship between flow stress and applied strain-rate for the laminated structure.
Examination of In-Service Coating Degradation in Gas Turbine Blades Using a Small Punch Testing Method
Authors: Kameda J. , Bloomer T. E. , Gold C. R. , Sugita Y. , Ito M. , Sakurai S.
Published: April 2011

This paper describes examination of in-service coating degradation in land based gasturbine blades by means of a small punch testing (SP) method and scanning Auger microprobe(SAM). SP tests on coated specimens with unpolished surfaces indicated large variations ofthe mechanical properties because of the surface roughness and curvature in gas turbine blades, SP tests on polished specimens better characterized the mechanical degradation of bladecoatings. The coated specimens greatly softened and the room temperature ductility of thecoatings and substrates tended to decrease with increasing operation time. The ductile-brittletransition temperature of the coatings shifted to higher temperatures during the bladeoperation. From SAM analyses on fracture surfaces of unused and used blades, it has beenshown that oxidation and sulfidation near the coating surface, which control the fractureproperties, result from high temperature environmental attack.
Tribological Properties of Ti/Tin Nanomultilayers
Authors: Houdy Ph. , Psyllaki P. , Labdi S. , Suenaga K. , Jeandin M.
Published: April 2011

The tribological behaviour of Ti/TiN amorphous nanometric multilayers is reported in comparison with that of single Ti and TiN layers, in order to study the wear mechanism of nanostructures submitted to that one may call “macroscopic loading”. Ti/TiN nanolayers were deposited onto Si substrate by high vacuum diode r.f. sputtering assisted by in-situ kinetic ellipsometry. Transmission Electron Microscopy (T.E.M.) characterization exhibited the multilayered structure of the films, ascertained by grazing angle X-ray reflectometry and ellipsometry. Sliding wear tests against alumina in dry air showed the ceramic-typed behaviour of the multilayers, the wear of which was partly governed through a microfracture mechanism. Their wear lifetime was found to be higher than that of Ti and TiN single layers and increased with the number of layers.
Indenter Geometry Effects on The Measurement of Mechanical Properties by Nanoindentation with Sharp Indenters
Authors: Tsui T. Y. , Oliver W. C. , Pharr G. M.
Published: April 2011

The measurement of mechanical properties by nanoindentation methods is most often conducted using indenters with the Berkovich geometry (a triangular pyramid) or with a sphere. These indenters provide a wealth of information, but there are certain circumstances in which it would be useful to make measurements with indenters of other geometries. We have recently explored how the measurement of hardness and elastic modulus can be achieved using sharp indenters other than the Berkovich. Systematic studies in several materials were conducted with a Vickers indenter, a conical indenter with a half-included tip angle of 70.3°, and the standard Berkovich indenter. All three indenters are geometrically similar and have nominally the same area-to-depth relationship, but there are distinct differences in the behavior of each. Here, we report on the application of these indenters in the measurement of hardness and elastic modulus by nanoindentation methods and some of the difficulties that occur.
In-Situ Tem Investigation During Thermal Cycling of thin Copper Films
Authors: Keller R.-M. , Sigle W. , Baker S. P. , Kraft O. , Arzt E.
Published: April 2011

In-situ transmission electron microscopy (TEM) was performed to study grain growth and dislocation motion during temperature cycles of Cu films with and without a cap layer. In addition, the substrate curvature method was employed to determine the corresponding stresstemperature curves from room temperature up to 600°C. The results of the in-situ TEM investigations provide insight into the microstructural evolution which occurs during the stress measurements. Grain growth occurred continuously throughout the first heating cycle in both cases. The evolution of dislocation structure observed in TEM supports an explanation of the stress evolution in both capped and uncapped films in terms of dislocation effects.
Simultaneous Overall and Local Stress Analysis of Thin Metal Films by Light Scattering and Beam Deflection Measurements
Authors: Kylner C. , Mattsson L.
Published: April 2011

We have developed an optical instrument for real-time overall stress as well as local stress relaxation measurements. The physical principle of the instrument is based on the fact that when a sample is exposed to heating the overall film stress bends the substrate and hillocks, the evidence of the local stress relaxation, form on the surface. Early hillock formation can be observed in real-time with integrated scattering technique, but the overall stress can be readily observed by laser beam deflection. Our instrument integrates laser beam deflection and light scattering techniques to achieve simultaneous overall stress and local stress relaxation measurements. A stress study is presented for an aluminium thin film on a silicon substrate.
Thin Film Polymer Stress Measurement Using Piezoresistive Anisotropically Etched Pressure Sensors
Authors: Bitko G. , Harries R. , Matldn J. , McNeil A. C. , Monk D. J. , Shah M. , Wertz J.
Published: April 2011

Silicon bulk micromachined piezoresistive pressure sensors are very sensitive to applied stresses: that is, applied pressure and/or packaging-related stresses. Device encapsulation has been observed to affect the electrical output of the pressure sensor significantly. The magnitude of the zero applied pressure output voltage (i.e., the offset voltage) that can be attributed to a thin film encapsulant is proportional to the magnitude of the roomtemperature thermal stress of that film. Parylene C coatings have been used as encapsulants in this work. Finite element and analytical modeling techniques were used to evaluate the effect of material property variation on the offset of a pressure sensor. A simple, linear expression of offset as a function of a material property parametric group, that includes: parylene thickness, parylene biaxial modulus, parylene CTE, silicon thickness, and annealing temperature; has been established. Experimental analysis of parylene coated pressure sensors and parylene coated silicon and gallium arsenide wafers was performed to confirm the resulting model. Known variations in parylene material properties caused by processing (i.e., uncontrolled deposition, annealing, and high temperature storage) have been used as an experimental vehicle for this purpose. An empirical relationship between offset voltage on parylene coated devices and room-temperature thermal stress on parylene coated wafers that have been exposed to the same processing is a linear expression with a similar slope to the modeling results. Furthermore, stress measurements from parylene coated silicon wafers and parylene coated gallium arsenide wafers have been used to estimate the parylene biaxial modulus (approximately 5000 MPa) and the parylene CTE (approximately 50 ppm/°C) independently. These material properties were observed to shift following parylene annealing and high temperature storage exposure experiments in a manner that is consistent with the established model.
Determination Of The α-Al2O3(0001) Surface Relaxation and Termination by Measurements of Crystal Truncation Rods
Authors: Guenard P. , Renaud G. , Barbier A. , Gautier-Soyer M.
Published: April 2011

We have investigated the unreconstructed (0001) surface structure of sapphire (α-Al2O3) by Grazing Incidence X-ray Scattering. Modulations along the crystal truncation rods were analyzed in order to determine the chemical nature of the terminating plane, and the structural relaxations of the first few atomic planes below the surface. The most likely model yields a single Al layer termination with relaxations of the first four planes of -51%, +16%, -29% and +20% respectively. These results compare well with the most recent theoretical calculations on this surface.
Near-Edge X-Ray Absorption Fine Structure Examination of Chemical Bonding in Sputter Deposited Boron and Boron-Nitride Films
Authors: Jankowski A.F. , Jimenez I. , Hayes J.P. , Shuh D.K. , Tong W.M. , Sutherland D.G.J. , Carlisle J.A. , Terminello L.J. , Himpsel F.J.
Published: April 2011

Near-edge x-ray absorption fine structure (NEXAFS) is used to examine the chemical bonding in boron and boron-nitride films sputter deposited from a fully-dense, pure boron target. Reactive sputtering is used to prepare the boron-nitride and multilayered films. Although the process of sputter deposition often produces films that lack long range order, NEXAFS reveals the distinguishing features of sp2 and sp3 hybridization that are associated with different crystalline structures. The sensitivity of NEXAFS to local order further provides details in bonding modifications that exist in these films.
Resonance Photoemission at the 2p Excitation Threshold of Ni3Al
Authors: HSU Li-Shing , Tsang K.-L. , Chung S.-C.
Published: April 2011

A marked resonance enhancement of the 3d photoemission intensity in angle-integrated electron-distribution curves from Ni3Al has been observed 6.6 eV below the Fermi level for photon energies in the vicinity of the Ni 2p absorption threshold. Soft x-ray L-edge absorption spectra were measured to determine the Ni 2p excitation threshold. The Fano asymmetry parameter and the effective Coulomb interaction for Ni3Al are 2.2 and 4.8 eV, respectively, as derived from the experimental data. Differences between the 2p→3d and the 3p→3d resonance effect are discussed, and comparisons with Ni, NiAl, and NiGa are made.
X-Ray Microscopy Of Multiphase Polymeric Materials
Authors: Ade H. , Smith A. P. , Zhuang G. R. , Wood B. , Plotzker I. , Rightor E. , Liu D.-J. , Lui S.-C. , Sloop C.
Published: April 2011

We have utilized the scanning transmission x-ray microscope at Brookhaven National Laboratory to acquire high energy resolution spectra of various polymers and to investigate the bulk characteristics of multiphasic polymeric materials with chemical sensitivity at a spatial resolution of about 50 nm. We present studies ranging from phase separated liquid crystalline polyesters and polyurethanes to various polymer blends. Improvements in the NEXAFS imaging and spectral acquisition protocol in the recent past provide much improved spectral fidelity and include in situ energy calibration with CO2.
Structure and Morphology of MBE Fabricated Zn0.5Fe0.5Se On GaAs as a Function of Substrate Preparation and Growth Temperature
Authors: Wei H.-Y. , Salamanca-Riba L. , Smathers J. , Jonker B. T.
Published: April 2011

We have recently reported the observation of CuAu-I, CuPt, and Cu3Au ordered structures in the diluted magnetic semiconductor Zn1−xFexSe grown by molecular beam epitaxy for different values of the Fe concentration. In the present work, we grew a series of samples with identical Fe composition (x=0.5) but for a range of growth temperatures (from 250 °C to 450 °C). By using transmission electron microscopy, ordering along the <001> and <110> directions was observed in both electron diffraction patterns and cross-sectional high-resolution lattice images corresponding to the CuAu-I ordered structure of Zn0.5Fe0.5Se. However, this ordered structure coexists with a tetragonal FeSe structure and forms large, well defined faceted domains. At the higher growth temperature, the number of faceted domains increases as observed by atomic force microscopy. Pure FeSe films were also grown at different temperatures for comparison. The influence of substrate preparation before film growth is also discussed.
Structural and Electrical Properties of Hgx Zn1−x S Thin Films Prepared by Flash Evaporation Technique
Authors: Swain P. K. , Sehgal H. K. , Misra D.
Published: April 2011

Electron diffraction investigations carried out on flash evaporated mercury zinc sulphide films with mercury concentration ( atomic percentage, x ) in the range 0.16 ≤ x ≤ 0.84 grown on freshly cleaved single crystal KCl substrates maintained at temperatures (Ts) between 65°C and 225°C indicate the films grow as single phase ternary alloy films with b.c.c. structure. Presence of a single phase alloy of the type HgxZn1−xS in the films is corroborated by a single absorption edge observed in the optical absorption measurements. The lattice parameter varies between 5.26Å and 4.52 Å as ‘x’ is varied between 0.16 and 0.84. The lattice parameter is observed to decrease slightly with increase of Ts for all compositions. The average grain size is observed to increase between 0.020 microns and 0.058 microns with increase of Ts in all films. Results of room temperature d.c. resistivity measurements show the resistivity to decrease with increase in mercury concentration ‘x’ in the films at a given Ts; ( for ‘fs=225°C, ρ(x=0.16) = 100.6 Ω-cm and ρ(x=0.84) = 10−0.4 Ω-cm ). The resistivity of films with a particular mercury concentration is, however, observed to increase with increase in the substrate temperature; ( for x=0.84 film, typical resistivity values are, ρ(Ts = 65 C) =10−2 Ω-cm and ρ(Ts = 225 C) = 10−0.4 Ω-cm). The observed resistive behavior of the films hints towards predominant grain boundary conduction in the films.
Transmission Electron Microscopy Stjudy of Initerface Microstrucure in ZnO Thin Films Grown on Various Substrates (Glass,Au,Sl,α-Al2O3)
Authors: Yoshino Y. , Iwasa S. , Aoki H. , Deguchi Y. , Yamamoto Y. , Ohwada K.
Published: April 2011

Zinc oxide (ZnO) thin films have been grown by radio frequency sputtering on glass, Al, Au and R cut sapphire substrates. Microstructures of the ZnO / substrate interface have been observed by transmission electron microscope. The purpose of this study is to elucidate the crystal growth mechanism of ZnO thin films using various substrates that have different crystallinity and crystal structures. An amorphous layer with a thickness of about 5 nm is observed at the ZnO/glass interface, and c axis orientation perpendicular to the substrate is observed on this amorphous layer. Mianstructurts at the ZnO/buffer metal interface, on the other hand, are significantly different from those of ZnO/glass interface. A thick amorphous layer of about 15 nm is observed at the ZnO/Al interface, presumably consisting of Al2O3 interface layer material. ZnO thin film grown on Au buffer layers is distinctly different from both ZnO on glass and Al. No amorphous layer is formed at the ZnO/Au interface, and c axis orientation begins directly from the Au surface. Epitaxially grown ZnO thin film is confirmed on a R-cut sapphire substrate. These results dearly demonstrate that ZnO thin films prepared by radio frequency sputtering are strongly influenced by the substrate surface crystallinity at the topmost layer of the substrate.
Structural and Chemical Properties of MBE Grown Niobium Overlayers on (110) Rutile
Authors: Marien J. , Wagner T. , Rühle M.
Published: April 2011

Thin Nb films were grown by MBE in a UHV chamber at two different temperatures (50°C and 950°C) on the (110) surface of TiO2 (rutile).

At a growth temperature of 50°C, reflection high energy electron diffraction (RHEED) revealed epitaxial growth of Nb on rutile: (110)[001] TiO2 ¦¦ (100)[001] Nb. In addition, investigations with Auger electron spectroscopy (AES) revealed that a chemical reaction took place between the Nb overlayer and the TiO2 substrate at the initial growth stage. A 2 nm thick reaction layer at the Nb/TiO2 interface has been identified by means of conventional transmission electron microscopy (CTEM) and high-resolution transmission electron microscopy (HRTEM).

At a substrate temperature of 950°C, during growth, the Nb film was oxidized completely, and NbO2 grew epitaxially on TiO2. The structure and the chemical composition of the overlayers have been investigated by RHEED, AES, CTEM and HRTEM. Furthermore, it was determined that the reaction of Nb with TiO2 is governed by the defect structure of the TiO2 and the relative oxygen affinities of Nb and TiO2.
Study on Thermal Stability of Thin CoSis Film
Authors: Gu Zhi-Guang , Chu Paul K. , Liu Jing , Jiang Guo-Bao , Ru Guo-Ping , Li Bing-Zong
Published: April 2011

The thermal stability of thin CoSi2 films formed from four layered structures: Co/Si, TiN/Co/Si, Co/Ti/Si and TiN/Co/Ti/Si has been studied using four-point-probe (FPP), TEM and RBS/channeling. It is found that thermal instability can be influenced by the polycrystalline structure in CoSi2. Growing epitaxial CoSi2 film on Si (100) using TiN capping and Ti interfacial layers can improve the thermal stability of thin CoSi2 film.
Stress and Microstructural Evolution of Lpcvd Polysilicon Thin Films During High Temperature Annealing
Authors: Yu Chia-Liang , Flinn Paul A. , Lee Seok-Hee , Bravman John C.
Published: April 2011

The mechanisms of stress generation and stress relaxation of LPCVD silicon thin films were studied using high temperature wafer curvature measurements. The stresses generated during depositions are measured as functions of deposition temperature and microstructure. Amorphous silicon deposited with a compressive stress shows a large stress change toward tensile during crystallization. The stress relaxation of polysilicon films deposited with tensile stresses can be described by a deformation model from Ashby and Frost [1]. The polysilicon films deposited with compressive stresses have hydrogen incorporated during deposition and shows hydrogen evolution during thermal cycles.
Monte Carlo Modeling of Atom Transport During Directed Vapor Deposition
Authors: Groves J. F. , Wadley H. N. G.
Published: April 2011

Atomic vapor transport has been investigated in the low vacuum (5 – 100 Pa) supersonic gas jets encountered in directed vapor deposition processes using a combination of Direct Simulation Monte Carlo (DSMC) techniques and a bimolecular collision model. The DSMC code generates the velocity vector, pressure, and temperature field for the carrier gas flow. This data is used as an input to a bimolecular collision model of atomic vapor transport in the flow. In the collision model, calculation of directed momentum loss cross-sections allows the location of carrier gas/vapor atom collisions to be deduced, and the vapor atom velocity vectors for individual vapor atoms to be tracked from source to substrate. For atoms arriving at the substrate, the impact location and velocity vector are obtained, making possible calculation of deposition efficiency, film thickness, adatom energy, and impact angle. These are the key inputs for simulations of resulting film microstructure/morphology evolution. Preliminary results for atomic transport of Cu vapor in supersonic He flows compare favorably with previously reported experimental observations.
Scanning Transmission X-Ray Microscopy Study of TiSe2/NbSe2 Superlattices
Authors: Shin Hyun-Joon , Jeong Kwangho , Johnson David C. , Kevan Stephen D. , Noh Myungkeun , Warwick Tony
Published: April 2011

TiSe2/NbSe2 superlattices crystallized from elementally modulated films have been studied with a Scanning Transmission X-ray Microscope (STXM) at the Advanced Light Source. The samples exhibited structures in the plane of the film with sizes of the order of one micrometer. The chemical sensitivity of STXM allowed us to infer that the titanium in the superlattice exists predominantly in microcrystalline TiSe2, but that these microcrystals are interspersed with elemental titanium inclusions. The STXM images reflect the interfacial nucleation between the constituent layers characteristic of the kinetic trapping method.