bluuebunny/crossref_metadata_2025 huggingface dataset:
Strain Relaxation by Dislocation Arrays in Thin Films
Authors: Pant Prita , Baker Shefford P.
Published: June 2019

An analytical model for strain relaxation by misfit dislocation arrays in thin films is presented that takes into account all components of the strain tensor, including shear strains. The model is developed for (001) films and applied to strain relaxation in (011) oriented FCC metal films. Our results show that shear strains strongly influence the total strain energy of the film. Since both the critical strain for dislocation formation, and the equilibrium spacing of dislocations in arrays depend on the minimum energy values, these quantities are found to be different from those predicted by previous models. This model is useful for understanding both critical strain data and strain relaxation in films.
A CombinedAb Initioand Bond-Order Potentials Study of Cohesion in Iridium
Authors: Cawkwell Marc J. , Nguyen-Manh Duc , Vitek Vaclav , Pettifor David G.
Published: June 2019

The extremely high melting point and excellent resistance to oxidation and corrosion offered by iridium suggest numerous applications of this transition metal in static components at high temperatures and in aggressive environments. However, the mechanical and physical properties of f.c.c. Ir exhibit numerous anomalies when compared to other metals that crystallize in the f.c.c. structure. Notable examples include a negative Cauchy pressure, 1/2 (C12 – C44), brittle transgranular cleavage after a period of plastic flow even in pure single crystals and anomalous [ΆΆ0] branches in the phonon spectra. Atomistic studies of extended defects are needed to elucidate the origin of anomalous mechanical properties, such as brittleness. For this purpose we developed a Bond-Order Potential (BOP), anO(N)tight-binding formalism, employing physically transparent parameterizations that use experimental andab initiodata, generated in this study using the Full Potential Augmented Plane Wave plus Local Orbitals (APW+lo) method. The constructed BOP reproduces then both equilibrium as well as a variety of nonequilibrium properties of Ir and represents an excellent description of cohesion in f.c.c. Ir. This description of interatomic interactions is imminently suitable for studies of defects, such as dislocations and grain boundaries, that control plastic deformation and fracture.
Statistical Dislocation Dynamics – Multiplication and Long Range Interactions
Authors: Zaiser Michael , El-Azab Anter
Published: June 2019

We discuss dislocation multiplication and long range interactions in the framework of threedimensional (3-D) statistical dislocation dynamics. It is found that the long range interactions render the conservation equation for the ensemble-averaged dislocation density nonlinear and nonlocal. It is also shown that the conservation equation for the dislocation density must be supplemented by a gauge constraint in order to account for dislocation multiplication.
Generalized Quasicontinuum Approach to Atomistic-Continuum Modeling of Complex Oxides
Authors: El-Azab Anter , Trease Harold
Published: June 2019

A formalism of the quasicontinuum method suitable for atomistic-continuum modeling of oxide crystals is presented. Multiple interacting quasicontinua, one per sublattice, which overlap in the physical crystal space, are used to model the oxide crystals. The method is implemented with the shell model for atomic interactions in ionic crystals, along with the Wolf's method for treating the long-range forces. Results are presented for the structural relaxation of strained and unstrained Fe2O3 crystal under periodic boundary conditions.
Modeling of Corrosion Protection Provided by an Aluminum-Based Clad Exposed to Atmospheric Conditions
Authors: Presue Francisco J. , Kelly R.G.
Published: June 2019

A computational mass transport framework for occluded region corrosion was extended to study alloys exposed to the thin electrolytes characteristic of atmospheric corrosion. Of interest were the interactions of an aluminum-clad layer with its Al-substrate in the vicinity of a scratch. The model focuses on open circuit conditions and local galvanic couples. Accurate electrochemical kinetics for metallic clad and bare AA2024-T3 are used, including the observed decrease in the pitting potential with increasing chloride concentration. The model has been applied to studies of the parameters that affect the throwing power of metallic claddings (e.g., scratch size, [Cl-], ipass, idl). Two geometries were investigated: a 1-D model and a square sample (two spatial dimensions) with a scribed cross, the latter simulating to what is usually done experimentally in exposure testing. A quantitative computation of the throwing power of metallic cladding on AA2024-T3 in thin electrolytes was achieved, including the effect of the criterion for scratch protection. For the base case of electrochemical behavior studied, a loss of protection ability was observed between a scratch size of 50 μm and 500 μm for the most conservative protection criterion (i.e., protection is achieved when the potential of all points in the scratch is at or below the pitting potential of the cladding). When a less conservative protection criterion is used, the size of the scratch that can be protected increased to between 500 μm and 3500 μm.

The metallic cladding modeling also demonstrated the equivalence of reducing the ipass of the clad or increasing the idl for oxygen reduction on the AA2024-T3 on the size of the scratch that can be protected. A less than linear dependence was found between these parameters and the scratch size that can be protected. An order of magnitude reduction in ipass (or increase in idl) led to a decrease of anywhere from 40% to 90% in the scratch size that was protected. Two competing effects of increasing the chloride concentration in the thin electrolyte were observed. Higher chloride concentrations increased the throwing power (due to increased conductivity), but they also lowered the pitting potential of both the cladding and the base material. In our simulations, the former dominated the latter, indicating better protection of scratches at higher chloride concentrations, with the extent of the effect depending on the protection criterion used.
The Impact of Annealing on the Corrosion Mechanism of Copper Films
Authors: Ernur D. , Carbonell L. , Maex K.
Published: June 2019

We investigated the corrosion mechanism of copper films. Based on our results regarding the morphology of the Cu surface, examined by scanning electron microscopy (SEM) and focused ion beam (FIB), it is shown that with an inorganic acid-based model CMP solution corrosion is initiated at the grain boundaries. In contrast, for an organic acid-based solution, corrosion starts with no preferential location. Some of the samples received an additional anneal after the CMP process was completed to monitor the influence of annealing on the corrosion mechanism by the acid solutions. Presence of facets especially after treatment with the inorganic acid-based model CMP solution suggests that a different mechanism governs the initiation and the evolution of corrosion. Desorption of the impurities during annealing, which is monitored by Atmospheric Pressure Ionized Mass Spectrometry (APIMS) revealed desorbing species from the copper films that could originate from the additives used in the Cu plating bath.
Nanocrystalline Germanium and Germanium Carbide Films and Devices
Authors: Niu Xuejun , Booher Jeremy , Dalal Vikram L.
Published: June 2019

Nanocrystalline Ge and its alloys with C are potentially useful materials for solar cells, thin film transistors and image sensors. In this paper, we discuss the growth and properties of these materials using remote, low pressure ECR plasma deposition. The materials and devices were grown from mixtures of germane, methane and hydrogen. It was found that high hydrogen dilutions (>40:1) were needed to crystallize the films. Studies of x-ray spectra revealed that the grains were primarily <220> oriented. The grain size was a strong function of hydrogen dilution and growth temperature. Higher growth temperatures resulted in larger grain size. High hydrogen dilution tended to reduce grain size. These results can be explained by recognizing that excessive amounts of bonded H can inhibit the growth of <220> grain, which is the thermodynamically favorable direction for grain growth. Grain sizes as large as 80 nm were obtained in nc-Ge. Addition of C reduced the crystallinity. Mobility and carrier concentrations in nc-Ge were measured using Hall effect. Mobility values of ˜5cm2/V-sand carrier concentrations of ˜1x1016/cm3were obtained in larger grains. p+nn+ devices were fabricated on stainless steel substrates and compared with similar devices deposited in nc-Si:H. It was found that the voltage decreased and current increased in nc-Ge devices, in comparison with devices in nc-Si:H. Addition of C to Ge devices increased the open circuit voltage and shifted the quantum efficiency to larger photon energies, as expected.
Effect of Fermi Level Position in Intrinsic a-Si:H on the Evolution of Defect States under Light Exposure.
Authors: Zeman M. , Nádaždy V. , Durný R. , Metselaar J.W.
Published: June 2019

The evolution of the programmed defect-state distributions in intrinsic hydrogenated amorphous silicon (a-Si:H) due to light soaking was qualitatively determined from charge deep-level transient spectroscopy. The defect-state distribution in a-Si:H was programmed by applying a particular bias voltage on the metal-oxide-semiconductor structure while annealing the structure above the equilibration temperature. The programmed distributions simulate defect-state distributions in different parts of an actual a-Si:H solar cell, particularly in the intrinsic regions close to the p/i and i/n interfaces.

The defect-state distribution in the bulk of the intrinsic layer is characterized by comparable contributions from the positively charged defect states above midgap, Dh, neutral states, Dz, and negatively charged states below midgap, De. In the programmedp-type (n-type) defect-state distribution there is an excess of the Dh (De) states. Light exposure modifies the p-type distribution that evolves to a broad distribution of states with a maximum around midgap. This distribution is dominated by Dz states with substantial contributions from Dh and De states. In case of n-type distribution light soaking only slightly influences the distribution by removing a part of the Dh states and by a small increase of Dz and De states.
Observation of a Hydrogen Doublet Site in High Defect Density As-Grown a-Si:H by 1H NMR
Authors: Bobela D. , Su T. , Taylor P. C. , Ganguly G.
Published: June 2019

1H NMR studies of hydrogenated amorphous silicon (a-Si:H) with ˜1017 cm-3 defects grown by PECVD with a rate of 5 Å/s show the existence of a hydrogen doublet for both asgrown and light-soaked samples. We observe the doublet over the temperature range from 5 to 20 K in a sample where no light soaking has occurred. The doublet line shapes display no narrowing over this temperature range. Vibrational modes characteristic of SiH2 wagging and scissor modes are seen from infrared spectroscopy. These results suggest that the doublet is due to SiH2 that occurs at a density of approximately 1 at. % in this sample. From line shape analysis, we estimate a lower limit of 1.8 ˜ for the hydrogen-to-hydrogen separation.
Growth of “New Form” of Polycrystalline Silicon Thin Films Synthesized by Hot Wire Chemical Vapor Deposition
Authors: Middya A. R. , Liang J-J. , Ghosh K.
Published: June 2019

In this work, we report on next-generation hot wire chemical vapor deposition technique, we call it ceramics hot-wire CVD. Using a new concept of rectangular ceramics filament holder and “confinement of thermal radiation from the filament”, a “new form” of polycrystalline silicon thin films has been developed at low temperature (˜ 250°C). The grains are found to be symmetrically distributed in array along the parallel lines, in (111) direction. On the surface of individual grains, “five-fold” and “six-fold” symmetries have been observed and we suspect that we developed “buckyball” type “giant silicon molecular solids” with different crystalline silicon lattice other than standard single-crystal silicon structure. We observed rarely found “icosaderal” symmetry in silicon thin films. This hypothesis has been supported by multiple Raman active transverse optical modes and the crystallographic structure analyzed by X-ray diffraction.
Nanocrystalline-Si Thin Film Deposited by Inductively Coupled Plasma Chemical Vapor Deposition (ICP-CVD) at 150°C
Authors: Han Sang-Myeon , Park Joong-Hyun , Lee Hye-Jin , Shin Kwang-Sub , Han Min-Koo
Published: June 2019

Nanocrystalline silicon (nc-Si) films were deposited by inductively coupled plasma chemical vapor deposition (ICP-CVD) at 150°C. ICP power was 400W. The process gas was SiH4 diluted with He as well as H2. The flow rate of He, H2 and He/H2 mixture was varied from 20sccm to 60sccm and that of SiH4 was 3sccm. X-ray diffraction (XRD) patterns of the nc-Si films were measured. From the XRD results of nc-Si films deposited by ICP-CVD, the properties of Si film deposited under each condition were studied. As the dilution ratio increases and He/H2 mixture was used as a dilution gas, intensities of <111>and<220> peaks were increased and the incubation layer was thin. These results were explained in the point of role of H2 plasma and He plasma in the nc-Si deposition process. Our experimental results show that nc-Si film deposited by ICP-CVD may be suitable for an active layer of nc-Si TFTs.
Doping Dependence of Chlorine Incorporation in SiC14-based Microcrystalline Silicon Films
Authors: Beyer Wolfhard , Carius Reinhard , Zastrow Uwe
Published: June 2019

For SiCl4-based microcrystalline silicon films the doping dependence of chlorine and hydrogen incorporation was studied. The results reveal a Fermi level dependence with a maximum chlorine (and hydrogen) incorporation for a Fermi level somewhat above midgap. As an explanation, a Fermi level dependence of the chlorine release rate during film growth is considered, similar as valid for hydrogen diffusion and desorption.
Initial Stage Hydrogen Movement and IR Absorption Proportionality Constants In Hot-Wire Deposited SiN1.2:H During High-Temperature Annealing
Authors: Goldbach H.D. , Verlaan V. , Werf C.H.M. van der , Arnoldbik W.M. , Rieffe H.C. , Romijn I.G. , Weeber A.W. , Schropp R.E.I.
Published: June 2019

Silicon nitride (SiNx:H) layers were deposited using a high deposition rate Hot-Wire CVD technique (up to 5 nm/s) and their application as passivating antireflection coating on multicrystalline silicon solar cells was investigated. An important aspect is the hydrogen release and diffusion during a short annealing treatment at temperatures well above the deposition temperature. Such annealing treatments (firing) are used during contact formation of multicrystalline solar cells.

A series of SiNx:H layers with Si/N ratio in the range of 0.7-1.45 was first characterized using optical R/T measurements, Fourier Transformed Infrared Spectroscopy (FTIR) and Elastic Recoil Detection (ERD) to determine optical constants n and k, Si-H, N-H and Si-N bond densities, Si-H peak position and H content. To get more insight in the passivation process during firing, which takes place at roughly 800 °C, samples with a N/Si ratio of 1.2 were annealed at this temperature for different times (15 s – 10 min). The total bonded H content, measured with FTIR, using conventional proportionality constants as proposed by Lanford and Rand [1], seems to show an increase within the first 60 s. At longer annealing times, the bonded H content decreases, as expected. The behavior of the H content under annealing measured by FTIR and ERD can be explained by using different matrix elements for calculating the H content from the FTIR data. The matrix element for the N-H stretching mode (3343 cm-1) was determined to be (4.7±0.2)x1020 cm-2 while the Si-H stretching (2193 cm-1) was found to be (0.55±0.04)x1020 cm-2. Such high matrix elements for the N-H stretching mode have not been reported earlier. The value of the Si-H stretching mode matrix element is within the reported values for different back bonding scenarios, but low for a peak position of 2193 cm-1. The ratio between the matrix elements of 8.5 differs strongly from the ratio of 2 observed by Lanford [1] or Bohne [2].
Micro-crystalline silicon-germanium thin films prepared by the multi-target RF sputtering system
Authors: Ajiki Toru , Nakamura Isao , Isomura Masao
Published: June 2019

Micro-crystalline silicon-germanium (μc-SiGe) films were prepared by the multi-target RF sputtering system using Ar and Ar-H2 mixture gases. The crystallization temperature of Si0.3Ge0.7 films is reduced from 600 °C to 400 °C by the introduction of H2 into the sputtering gases. The dark conductivity of 1.7x10-7 S/cm and one order of magnitude of photosensitivity are obtained with the H2/Ar flow ratio of 2. The activation energy of dark conductivity is 0.42 eV, which is a half of the energy gaps of Si0.3Ge0.7, and show that the films have intrinsic nature. Besides, the absorption coefficients are similar to those of single crystalline Si0.3Ge0.7. The results suggest that the H2 introduction is effective both to reduce the dangling bond defects and to decrease the crystallization temperature of the μc-SiGe films.
Poly-crystalline Ge thin films prepared by RF sputtering method for thermo photo voltaic application
Authors: Hoshi Daisuke , Nakamura Isao , Isomura Masao
Published: June 2019

The poly crystalline Ge films were prepared by the RF sputtering method with Ar and Ar-H2 mixture gases. The crystallization temperature increases from 400 °C to 500 °C due to the H2 introduction into the sputtering gases. On the other hand, the H2 introduction decreases the absorption coefficients in the long wavelength region corresponding to lower energy values than the energy gap of Ge, although much higher absorption coefficients are observed in the case of the Ar sputtering. Probably, the gap state density decreases due to the hydrogen termination of dangling-bonds in the grain-boundaries. The (220) preferential orientation is stressed and the highest Hall mobility is obtained with 75% of the gas flow ratio [Ar/ (Ar+H2)]. The preferential growth probably causes higher quality Ge films.
Mechanical Properties of Porous MSQ Films: Impact of the Porogen Loading and Matrix Crosslinking.
Authors: Ciaramella F. , Jousseaume V. , Maitrejean S. , Rémiat B. , Verdier M. , Passemard G.
Published: June 2019

Semiconductor industry needs a continuously improvement of integrated circuits performance and an increase of integrated density on silicon. The 2004 ITRS Roadmap underlines the need of dielectric material for ILD with dielectric constant (k) lower than 3 for the 90 nm node and than 2.4 for the 45 nm node. In this work, porous films with k value lower than 2.2 were processed using a porogen approach. Firstly, a material composed of a methylsilsesquioxane (MSQ) matrix and of organic nanoparticles (called porogen) is deposited and baked. Then, this composite is thermally cured to allow the porogens degradation and matrix crosslinking. Different k values were obtained by varying the porogen loading in the composite. Mechanical properties of composite and porous films (before and after porogen removal respectively) were investigated using nanoindentation and FTIR analysis for different porogen loadings (between 0 and 40 %). The composite modulus is higher than the porous film modulus for high porogen loading. This result is interpreted in term of matrix crosslinking. Mechanical properties were also modelized using foam mechanical models. For high porosity level, the best Young modulus fitting is obtained with tetrakaidecaedric cells, which seems in good agreement with porosity morphology.
A Study of Impact Reliability of Lead-free BGA Balls on Au/Electrolytic Ni/Cu Bond Pad
Authors: Ou Shengquan , Xu Yuhuan , Tu K. N. , Alam M. O. , Chan Y. C.
Published: June 2019

The most frequent failure of wireless, handheld, and movable consumer electronic products is an accidental drop to the ground. The impact may cause interfacial fracture of wire-bonds or solder joints between a Si chip and its packaging module. Existing metrologies, such as ball shear, and pull test cannot well represent the shock reliability of the package. In this study, a micro-impact machine is utilized to test the impact reliability of three kinds of lead-free solders: 99Sn1Ag, 98.5Sn1Ag0.5Cu and 97.5Sn1Ag0.5Cu1In (hereafter called Sn1Ag, Sn1Ag0.5Cu, and Sn1Ag0.5Cu1In). The effect of thermal aging on the impact toughness is also evaluated in this study. We find a ductile-to-brittle transition in SnAg (Cu) solder joints after thermal aging. The impact toughness is enhanced by the thermal aging. This is a combination effect of the growth of intermetallic compound (IMC) at the interface provided strong bonding, and the softening of the solder bulk during the thermal aging absorbed more energy during plastic deformation.
Nanoporous Materials Integration Into Advanced Microprocessors
Authors: Todd Ryan E. , Labelle Cathy , Nitta Satya , Fuller Nicholas C.M. , Bonilla Griselda , McCullough Kenneth , Taft Charles , Lin Hong , Simon Andrew , Simonyi Eva , Malone Kelly , Sankarapandian Muthumanickam , Dunn Derren , Zaitz Mary Ann , Cohen Steve , Klymko Nancy , Moon Bum Ki , Li Zijian , Li Shuang , Yan Yushan , Liu Junjun , Ho Paul S.
Published: June 2019

Future microprocessor technologies will require interlayer dielectric (ILD) materials with a dielectric constant (κ-value) less than 2.5. Organosilicate glass (OSG) materials must be nanoporous to meet this demand. However, the introduction of nanopores creates many integration challenges. These challenges include 1) integrating nanoporous films with low mechanical strength into conventional process flows, 2) managing etch profiles, 3) processinduced damage to the nanoporous ILD, and 4) controlling the metal/nanoporous ILD interface. This paper reviews research to maximize mechanical strength by engineering optimal pore structures, controlling trench bottom roughness induced by etching and understanding its relationship to pore size, repairing plasma damage using silylation chemistry, and sealing a nanoporous surface for barrier metal (liner) deposition.
Determining Pore Structure and Growth Mechanisms in Templated Nanoporous Low-k Films
Authors: Peng Hua-Gen , Vallery Richard S. , Liu Ming , Frieze William E. , Gidley David W. , Yim Jin-Heong , Jeong Hyun-Dam , Kim Jongmin
Published: June 2019

Templating is one of the most popular methods for generating nanocomposite and nanoporous films and the resultant pore size and pore interconnection length depend strongly on porogen concentration/porosity among other factors. Positronium Annihilation Lifetime Spectroscopy (PALS) analysis has been performed on a series of films produced using increasing concentrations of a type of cyclodextrin (CD) porogen in a modified silsesquioxane host matrix. PALS reveals the relationship between the resulting pore structure (both size and interconnection length) and porosity, which can be used to deduce pore shape. At low porogen concentration, isolated pores are resolved, but the pore size is consistent with a cluster of two or three CD molecules, rather than an individual one. As the porosity increases, the aggregation of the porogen domains appears to be more 3-dimensional (pseudo-random) with gradual increase in pore size. Computer simulations using a random pore growth model show consistent trends for pore size growth, but the agreement is poor for interconnection length. It is a key demonstration of the usefulness of PALS in untangling the fundamental pore structure and its evolution in porosity. PALS characterization of porosity provides novel feedback in the understanding and design of nanoporous materials.
Thermal Oxidation of Cu Interconnects Capped with CoWP
Authors: Gambino J. , Smith S. , Mongeon S. , Meatyard D. , Chen F. , DeHaven P.
Published: June 2019

The thermal oxidation of Cu interconnects, at 350°C in air, has been studied as a function of thickness of a CoWP capping layer. For thin CoWP layers (25 nm), a thick oxide layer (200 nm) is formed which is mainly composed of Cu20. For thick CoWP layers (50 nm), the oxide layer is much thinner (36 nm) and is mainly composed of CoO. For both CoWP thicknesses, depletion of the underlying Cu is often observed after oxidation and whisker growth is often observed on the surface. The results are consistent with an oxidation mechanism where metal is the dominant diffusing species. For thin CoWP layers, Cu diffuses more quickly to the surface than Co, and therefore mainly Cu oxides are formed. For thick CoWP layers, the Cu diffusion to the surface is greatly reduced, and as a result, mainly Co oxides are formed. These results indicate that CoWP is not a good barrier for thermal oxidation, so high temperature exposure to oxidizing ambients must be minimized during processing of integrated circuits where CoWP is used instead of a dielectric barrier.
Effect of Microstructure and Dielectric Materials on Stress-Induced Damages in Damascene Cu/Low-k Interconnects
Authors: Joo Young-Chang , Paik Jong-Min , Jung Jung-Kyu
Published: June 2019

The line width dependence of stress in damascene Cu was examined experimentally as well as with a numerical simulation. The measured hydrostatic stress was found to increase with increasing line width. The larger stress in an interconnect with large dimension is attributed to the larger grain size, which induce higher growth stress in addition to thermomechanical stress. A stress model based on microstructure was constructed and the contribution of the growth and thermal stress of the damascene lines were quantified using finite element analysis. It was found that the stress of the via is lower than that of wide lines when both the growth stress and thermal stress were considered. This stress gradient between via and line, which is the driving force of vacancy diffusion, is larger when the low-k with lower stiffness and higher thermal expansion is used for dielectric layer. For this reason, the Cu/low-k can be more vulnerable to stress-induced voiding.
Material Reliability and Integration Issues of Polyimide and Benzocyclobutene Interlayer Dielectric Materials
Authors: Zantye Parshuram B. , Kumar Ashok , Gopalkrishnan R. , Balakumar S.
Published: June 2019

The constant push for decreasing the Resistance-Capacitance (RC) delay has led to the implementation of Multilevel Metallization (MLM) scheme for interconnect wiring, Cu as the wiring material and low ê materials as Interlayer Dielectric (ILD). Polymeric materials are being explored to replace SiO2 based ILD materials in the next generation ICs. Several reliability and integration challenges arise during integration of the candidate polymeric ILD when they are subjected to planarization by Chemical Mechanical Polishing (CMP). In this research, we have performed a comparative study of certain candidate low ê materials: 1) undoped SiO2 (standard), 2) Polyimide and 3) Benzocyclobutene (BCB). We have studied the impact of reduction in dielectric constant on the mechanical and tribological properties, and the CMP performance of these ILD materials. The adverse effect of shear and mechanical abrasion due to decreased mechanical properties of the low ê materials induced numerous defects during CMP.
Effect of Current Direction on the Reliability of Different Capped Cu Interconnects
Authors: Gan C. L. , Lee C. Y. , Cheng C. K. , Gambino J.
Published: June 2019

The reliability of Cu M1-V1-M2-V2-M3 interconnects with SiN and CoWP cap layers was investigated. Similar to previously reported results, the reliability of CoWP capped structures is much better than identical SiN capped structures. However, it was also observed that the reliability of CoWP capped interconnects was independent of the direction of electrical current flow. This phenomenon is different from what was observed for SiN capped structures, where M2 lines with electron current flow in the upstream configuration (“via-below”) have about three times larger median-time-to-failure than identical lines in the downstream configuration (“viaabove”). This is because the Cu/SiN interface is the preferential void nucleation site and provides the fastest diffusion pathway in such an architecture. Failure analysis has shown that fatal partially-spanned voids usually had formed directly below the via for “via-above” configuration, and fully-spanned voids occurred in the lines above the vias for “via-below” configuration.

On the other hand, failure analysis for CoWP-coated Cu structures showed that partiallyspanned voids below the via do not cause fatal failures in the downstream configuration. This is because the CoWP layer is conducting, and thus able to shunt current around the void. As a result, a large fully-spanning void is required to cause a failure, just like the upstream configuration. Thus the lifetime of an interconnect with a conducting cap layer is independent of whether the current is flowing upstream or downstream.
Vertical integration of hydrogenated amorphous silicon devices on CMOS circuits
Authors: Wyrsch N. , Miazza C. , Ballif C. , Shah A. , Blanc N. , Kaufmann R. , Lustenberger F. , Jarron P.
Published: June 2019

Monolithic integration of sensing devices usually requires sharing the CMOS chip floor space between sensors and their readout electronics. Vertical integration of the sensor on top of the electronics allows one to have the full chip area dedicated to sensing. For light detection, the deposition of hydrogenated amorphous silicon (a-Si:H) photodiodes on top of CMOS readout circuits offers several advantages compared to standard CMOS imagers. The issues regarding the design of a-Si:H photodiodes, their integration and the influence of the CMOS chip design (i.e. its surface morphology) on a-Si:H diode performance are discussed. Examples of TFA sensors for vision and particle detection are also presented.
Rf Hollow Cathode Plasma Jet Depopsition of BaxSR1-XTI03 Films
Authors: Ianno N.J. , Soukup R.J. , Hubička Z. , Olejnčcek J. , Ŝíchová H.
Published: June 2019

An initial study of the RF hollow cathode plasma jet deposition of BaxSr1-xTiO3 has been performed. Deposition occurred from a single composite nozzle consisting of BaTiO3 and SrTiO3 at substrate temperatures on the 500-550 C range. It has been shown that film composition can be easily controlled by the nozzle composition as well as other deposition parameters. The as-deposited films exhibit clear BSTO peaks with grain size on the order of 30nm.
Growth of Uniform Nickel Wire Arrays
Authors: Yang Kun , Yeh W. J.
Published: June 2019

Nickel nanowire arrays with high aspect ratio and large packing densities have been grown in thin nanochannel glass templates by an electrochemical deposition method. The templates were polished and etched for enough time to obtain parallel, uniform, hollow channels. One of surfaces of templates was then deposited with copper to provide an electrode. The pH value of NiSO4 aqueous solution was 1 to 2 and the deposition potential was chosen to be –1.2 V versus the saturated Calomel electrode. Obtained nickel wires were circular, each approximately 80 – 160 nm in diameter and 150 μm long, depending on the diameter of nanochannel. Finally, scanning electron microscopy has been used to characterize the nanostructures. Magnetic properties of the nickel wire arrays have been also investigated by using a superconducting quantum interference device magnetometer (SQUID).
Use of Ferrofluid Patterns as Diffusion Masks
Authors: Halverson Derek , Yellen Ben , Kalghatgi Sameer , Friedman Gary
Published: June 2019

A novel method of dynamically and selectively controlling the diffusion of molecules using aggregation of ferrofluid is proposed. This method can be used to mask specific locations on a surface for combinatorial chemistry or to restrict diffusion of molecules in selected areas in a microfluidic device. This method works by using the controlled aggregation of stabilized 10nm diameter iron oxide particles (ferrofluid) to slow the diffusion of molecules in a similar manner as to how a porous media restricts diffusion. Dynamic aggregate formation is controlled by a magnetic pattern on a substrate in conjunction with an external field. The external magnetic field bias applied to the system causes ferrofluid to aggregate only in designated areas around the magnetic patterns thereby slowing diffusion through the areas where the aggregate clouds have formed.
Wafer Scale Nanopatterning and Nanomaterials Synthesis of Functional Nano Probes for Atomic Force Microscopy
Authors: Ye Qi Laura , Cassell Alan M. , Liu Hongbing , Meyyappan M.
Published: June 2019

The key hurdle in nanoscience and nanotechnology is the large-scale integration of nanoscale materials with micron scale electronics and structures to form functional devices and sensors. We have developed an innovative bottom-up wafer scale fabrication method that combines nanopatterning and nanomaterials synthesis with traditional silicon micromachining technologies. We have achieved nano-micro integration through catalyst nanopatterning and registration at wafer scale and through effective nanocatalyst protection and release before and after microfabrication. Our wafer scale fabrication process has produced 244 carbon nanotube (CNT) probes per 4-inch silicon wafer with control over the CNT location, diameter, length, orientation, and crystalline morphology. CNT probes with diameters of 40-80 nm and lengths of 2-6 μm are found to be functional nano probes for atomic force microscopy (AFM) imaging. In this paper, we will address our nano probe design and fabrication considerations in detail. CNT tip locations and diameters are defined by e-beam lithography. CNT length, orientation, and crystalline quality are controlled by the plasma enhanced chemical vapor deposition (PECVD) method. With effective catalyst protection schemes, this fabrication process is very similar to the conventional approach for fabricating wafer-scale silicon AFM probe tips. Process control is feasible and the overall yield is greatly improved. Our method and technology can be easily adapted to many other nanomaterials (nanotubes and nanowires) synthesis and processes for their rational design, fabrication, and integration in their applications.
Effect of substrate deformation in the nanowire/nanotube bending test
Authors: Chan Wingkin , Wang Yong , Li Jianrong , Zhang Tong-Yi
Published: June 2019

The present work analyses the effect of substrate deformation during the nanowire/nanotube bending test. An individual nanowire or nanotube is treated as a linear isotropic continuum. The substrate deformation is modeled by two coupled springs and the spring compliances arefunctions of the nanowire/nanotube diameter, and the Young moduli of the nanowire/nanotube and the substrates. An atomic potential is used to determine the adhesion between the nanowire/nanotube and its substrate. Consequently, a simple three dimensional Finite Element (FE) model is built to calculate the spring compliances. The load-displacement relation, which takes into account of substrate deformation, is derived in a closed form, which can be reduced to the load-displacement relations based on the simply-supported ends and the built-in ends. The numerical results indicate that the substrate deformation has a great influence on the determination of the Young modulus of a nanowire/nanotube from the bending test. The nanobridge test on carbon nanotubes is taken as an example to demonstrate the feasibility of the developed method.
Theory of large-scale electronic structure calculation and nanoscale mechanical property in fracture behavior of silicon
Authors: Hoshi Takeo , Takayama Ryu , Iguchi Yusuke , Fujiwara Takeo
Published: June 2019

Several theories and program codes were developed for large-scale atomistic simulations with fully quantum mechanical description of electron systems. The fundamental concepts are generalized Wannier state and Krylov subspace. Test calculations were carried out with upto 106 atoms using a standard workstation. How electronic state is described in large-scale calculation was demonstrated on Si(001)-(2×1) surface. As a practical application, cleavage fracture of silicon was simulated with 10-nm-scale samples for investigating its nanoscale mechanical behavior. Discussions are focused on the unstable (001) cleavage mode and the stable (experimentally observed) (111)-(2×1) cleavage mode. As well as elementary surface reconstruction, step formation and bending in cleavage path were observed. These results were compared with experiments, such as scanning tunneling microscope (STM).
Precessing of 2024 Al /W Composites Prepared by Powder Metallurgy
Authors: Yang Zhimin , Yang Jian , Lian Youyun , Mao Changhui
Published: June 2019

In this work, the 2024 Al/W composites were fabricated by powder metallurgy. W powders and gas-atomized 2024 Al aluminum powder were milled by ball milling with different milling parameters. The mixtures were consolidated by vacuum hot press under a pressure of 400MPa and then hot-extruded for a higher density. A T6 heat treatment was carried out for the samples, which consisted of solution treating at temperature 470-500, water quenching and artificial aging at 1900 for 8h. The microstructure of as-milled mixture powders and the composites were investigated by combination of X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM). The microstructure and its relationship with the mechanical properties of the composites were also investigated. The results show the milling-energy is a key factor for the processing of the composite. For the samples with high energy milling, Al atoms dissolved into W lattice gradually and finally formed a W solution after 6 hours milling, which can cause the a large amount of precipitation of WAl12, WAl5 in the following hot pressing process. With appropriate processing parameters, the tensile strength of the composite can reach 480 MPa.
Computational Modeling and Design of Adaptive Thin-Film Composite Coatings
Authors: Pearson James Deon , Zikry Mohammed A. , Rezvanian Omid
Published: June 2019

The tailoring of thin film coatings comprised of high strength constituents, such as diamond like carbon and partially stabilized zirconia and ductile constituents, such as gold and molybdenum is investigated by new microstructurally-based finite-element techniques for applications related to the wear, durability, and performance of these coatings over a broad range of temperatures and loading conditions. The effects of contact transfer films, grain-shape sizes and distributions, grain-boundary structure and sliding, texture, and strength are used to determine the optimal thin film coating compositions. Comparisons are made with experimental measurements and observations, and guidelines for optimal thin film composite coatings are proposed.
Simulation of Dislocation Relaxation in FCC Metals
Authors: Kogure Yoshiaki , Sakieda Kei , Kosugi Toshio , Nozaki Tadatoshi
Published: June 2019

Motion of edge dislocation in copper crystals is investigated by means of molecular dynamics simulation. The embedded atom method potential was used in the simulation. Configuration and motion of dislocations are graphically demonstrated in 3-dimentional model. Change of mean potential energy during the dislocation motion is also investigated.
Lattice Dynamics and Thermodynamics of Bcc Vanadium at High Pressures
Authors: Sha Xianwei , Cohen R. E.
Published: June 2019

We investigate the lattice dynamics and thermodynamics of nonmagnetic bcc vanadium as a function of temperature and pressure, using the first principles linear response linear-muffin-tin-orbital method. The calculated phonon density of states (DOS) show strong temperature dependence, different from inelastic neutron scattering measurements where the phonon DOS show little change from room temperature up to 1273 K. We obtain the Helmholtz free energy including both electronic and phonon contributions and calculate various equation of state properties such as the bulk modulus and the thermal expansion coefficient. A detailed comparison has been made with available experimental measurements.
Using the heat of recirculation gases of the ship main engine by an ejector refrigeration machine for intake air cooling
Authors: Radchenko R. , Konovalov D. , Pyrysunko M. , Radchenko M.
Published: June 2019

One of the promising ways in environmentalizing marine internal combustion engines is the neutralization of harmful substances in exhaust gases through particular gas recirculation (EGR-technology). However, the use of such techniques conflicts with the engine's energy efficiency. In the work presented, the scheme-design solution of the exhaust gas recirculation system with using the heat of recirculation gases by an ejector refrigeration machine for cooling the air at the intake of ship's main engine is proposed. The effect of using the heat of recirculation gases for cooling the air at the intake of the engine is analyzed taking into account the changing climatic conditions for a particular vessel's route line. It is shown that the use of an ejector refrigeration machine reduces the air temperature at the entrance of the main engine by 5-15 ° С, which reduces the specific fuel consumption by 0.5-1.5 g/(kW∙h). This reduces emissions of harmful substances when the engine is running with recirculation of gases, in particular, NOx by 30-35%; SOx by 10-12%.
Стенд для дослідження розширювальних турбомашин малої потужності та агрегатів на їх основі
Authors: Ванєєв С. М. , Мірошниченко Д. В. , Журба В. О. , Знаменщиков Я. В.
Published: June 2019

В даний час для вирішення проблем енергозбереження проводяться роботи з дослідження та використання малопотужних розширювальних машин для утилізаційних турбогенераторів. Перспективним є  створення  турбоагрегатів на базі відносно тихохідних вихрових розширювальних машин, але робіт по їх експериментальним дослідженням відомо мало. У зв'язку з цим необхідно створення матеріально-технічної бази, що включає нові і модернізовані стенди, експериментальні модельні та натурні установки, об'єкти дослідження, виробниче та технологічне обладнання, обчислювальні і програмні комплекси. У статті представлені результати розробки і тестування елементів стенду досліджень турбогенераторів малої потужності для утилізації енергії стиснутих газів. Створено експериментальний стенд, на якому можна проводити дослідження і випробування розширювальних турбомашин і турбогенераторів на їх основі різного конструктивного виконання потужності до 15 кВт, а також демонструвати роботу турбогенератора потенційним замовникам продукції. Прилади та обладнання стенду дозволяють плавно змінювати електричне навантаження і отримувати необхідні параметри і характеристики розширювальних машин і турбогенераторів. У складі стенду створена інформаційно-вимірювальна система, яка забезпечує контроль стану обладнання; здійснює реєстрацію інформації і обробку даних вимірювань з представленням результатів в табличному і графічному вигляді; забезпечує надійне зберігання отриманої інформації тощо. Створено дослідний зразок енергозберігаючого турбогенератора на основі вихрової розширювальної машини. Конструкція турбогенератора дозволяє досліджувати вплив основних геометричних параметрів проточної частини на ефективність вихрової розширювальної турбомашини і генератора в цілому. Результати роботи будуть  використані для дослідження розширювальних  турбомашин і утилізаційних турбогенераторів на їх основі, що використовують енергію стиснутого газу.
The relationship between the surface tension and the saturated vapor pressure of model nanofluids
Authors: Khliyeva O. Ya. , Ivchenko D. A. , Khanchych K. Yu. , Motovoy I. V. , Zhelezny V. P.
Published: June 2019

Information on surface tension is necessary for modeling boiling processes in nanofluids. It was shown that the problem of predicting the surface tension of complex thermodynamic systems, such as nanofluids, remains outstanding. It should be noted that the surface tension of liquids and the saturated vapor pressure are due to a specific intermolecular interaction in the region of spatial heterogeneity of the substance (surface layer). Moreover, the compositions of the surface layer of nanofluid and its liquid phase are not equal. The presence of nanoparticles in the base fluid affects the composition of the surface layer of liquids. However, there are no methods for determining the composition of the surface layer of nanofluids and this fact complicates establishing the dependence of the surface tension on the state parameters of nanofluids. It should be mentioned that the number of possible methodological errors in measurements of the saturated vapor pressure of nanofluids is significantly lower than for the surface tension measurements. Therefore, in the development of models for predicting the surface tension, scientific and practical interest has establishing the relationship between the surface tension and the saturated vapor pressure of nanofluids. In the presented work, we consider the nanofluids of isopropanol/Al2O3 nanoparticles and o-xylene/fullerenes C60. Saturated vapor pressure and surface tension of nanofluids of isopropanol/Al2O3 nanoparticles have been studied in the temperature range 293 – 363 K and concentrations of Al2O3 nanoparticles 0-8.71 g/kg. Measurement of saturated vapor pressure and surface tension of nanofluids of o-xylene/fullerenes C60 have been performed in the temperature range 283 – 348 K and the concentration of C60 0-7.5 g/kg. It is shown that additives of Al2O3  nanoparticles and fullerenes C60 lead to a decrease in the surface tension and increase in the saturated vapor pressure. It is shown that there is a universal dependence between the reduced surface tension and saturated vapor pressure for the researched nanofluids.
The shape of road markings for visibility computations
Authors: Crescenzo Giuseppe , Villa Céline , Brémond Roland , Vignali Valeria , Lantieri Claudio , Simone Andrea
Published: June 2019

Road markings visibility is usually assessed by means of the visibility level (VL). Several models have been developed to calculate the visibility distance on the road (Detect/PCDetect, Carve/Tarvip, Cost 331 and CIE 73). These models all approximate the visibility of a marking by estimating the diameter of an ‘equivalent’ disc. In this process, speculative hypotheses are made to calculate this diameter, labelled the equivalent area hypothesis, the equivalent perimeter hypothesis or the equivalent width hypothesis. To compare these hypotheses, a psychophysical experiment was conducted with eight participants and 120 stimuli. It was found that the merit of each hypothesis changed with the diameter of the equivalent disc. Above 0·1°, all the hypotheses gave good results, but the equivalent area hypothesis was found to be the best. Below 0·1°, the equivalent width hypothesis was more accurate, but further investigations are still needed.
Power Analysis by Simulation using R and simglm
Authors: LeBeau Brandon
Published: June 2019

Power is a task that is commonly done prior to collecting data for a primary study. In most cases closed-form solutions are used to estimate power which may statistical assumptions to be able to perform the computations, for example assume residuals are normally distributed. In real-world data, these statistical assumptions may not hold, therefore estimates of power when these assumptions are assumed will likely be inflated. Power by simulation is another way to compute power estimates and offers significant flexibility to the user to explore the impact of various statistical assumption violations may have on power. This tutorial uses the simglm R package to perform the power by simulation. The simglm package provides a framework to simulate data from generalized linear mixed models which includes a wide variety of models. In addition, functions to perform replications and to compute power estimate summaries are available for users to take advantage of. Two worked examples are shown, one for a two-sample t-test and another within a repeated measures or longitudinal framework.