bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nanoindentation of Amorphous and Nanostructured Polymers
Authors: Maner Kyle C. , Begley Matthew R. , Utz Marcel 
Published: June 2019

AbstractWe present a detailed nanoindentation study of micron-scale thin films of polystyrene (PS), poly(phenylene oxide) (PPO), poly(methyl methacrylate) (PMMA), a metal-centered PMMA-Ruthenium block copolymer, and a PS-poly(ethylene-propylene) (PS-PEP) block copolymer with lamellar morphology. The results show that size-dependence is most readily noticeable for the lamellar PS-PEP film, indicating that the nanoidentation approach has sufficient sensitivity to capture scale dependence on scales in the range of tens of nanometers. The less pronounced scale-dependence (or lack thereof) in the other films is discussed in the context of identifying the physical length-scale of elementary processes of plastic deformation. The results indicate that the upper limit on the size of plastic shear zones in amorphous polymers is approximately 1200-9600 nm3 (i.e. a sphere with a diameter in the range of 20-40 nm).
Energetics of Dislocation Nucleation under a Nanoindenter
Authors: Zhang Chuanli , Xu Guanshui 
Published: June 2019

AbstractDislocation nucleation under an idealized nanoindenter is analyzed based on the Peierls-Nabarro dislocation model. The variational boundary integral method is used to obtain the dislocation profiles that correspond to the shear displacements between the adjacent atomic layers along the slip plane. The critical condition for dislocation nucleation at absolute zero and the activation energies required to thermally activate dislocations from their stable to unstable saddle point configurations are determined. By treating the surface as part of an infinite crack embedded in the infinite medium, a rather straightforward approach is adopted to account for the surface effect. The emission of multiple dislocations from the surface of a film-substrate system is also studied. The size effects of the indenter width and film thickness are characterized by the typical load-displacement relation.
Microstructure and Mechanical Properties of Nanolayered TiN/Cu Thin Films
Authors: Tse Y.Y. , Abadias G. , Michel A. , Tromas C. , Jaouen M. 
Published: June 2019

AbstractStructural and mechanical properties of nanoscale TiN/Cu multilayers grown by dual ion beam sputtering with bilayer periods (A) ranging from 2.5 to 50 nm were studied. Both low-angle and high-angle X-ray diffraction (XRD) experiments have been employed to globally characterize the multilayers structure. The microstructure of the multilayers has been scrutinized by high resolution transmission electron microscopy (HRTEM). The effects of interface and bilayer thickness on hardness were investigated by depth-sensing nanoindentation technique. A small hardness increase with decreasing periodicity of the multilayers has been observed. The relationship between the hc/T ratio (hc is the contact depth and T is the total film thickness) and the hardness is established. The correlation between the microstructure and hardness is discussed.
A Mechanical Study of W and W2N Single Layers, and W2N/W Multilayers
Authors: Maillé L. , Sant C. , Aubert P. , Garnier P. 
Published: June 2019

AbstractThe microstructure of W, W2N single layers and W2N/W multilayers are related to their mechanical properties. We study the hardness of multilayers as function of the period thickness. Two partial pressures of nitride (PN2 = 10 % and 50 %) for W2N deposition are investigated. For the single layers, the hardness value increases with the nitrogen partial pressure. The hardness of W2N/W multilayers using PN2 = 50% for W2N deposition increases when the layer spacing decreased. A hardness value of 19.5 GPa is reached for a multilayer with PN2 = 50% and, close to 20 GPa with PN2 = 10% for all the period studied.
Dislocation patterning and recovery under single slip: modelling micromechanisms from observations
Authors: Veyssière Patrick , Chiu Yu-Lung , Grégori Fabienne 
Published: June 2019

AbstractThe paper focuses on the formation and on the role of prismatic loops during deformation. The analysis is restricted to non-diffusive processes in fcc-related crystals. Double cross-slip and cross-slip dipolar annihilation yield strings of loops such that one loop extremity is aligned in the screw direction with the extremity of its nearest neighbour. Reactions between prismatic loops and mobile dislocations are at the origin of a number of microstructural reactions including recovery, dislocation entanglements and patterning in single slip, dislocation multiplication and there is indication that they may nucleate twins.
Single Crystal Deformation Experiments for Validation of Dislocation Dynamics Simulations
Authors: Lassila David H. , LeBlanc Mary M. , Rhee Moono 
Published: June 2019

AbstractA new experimental apparatus has been developed for performing compression deformation experiments on high-purity Mo single crystals. These experiments provide data that can validate 3-D dislocation dynamics (DD) simulations. The experiments are performed under conditions that allow unconstrained deformation; thus, a relatively uniform state of axial stress is maintained during deformation. In the following sections, we describe the new experimental apparatus and our results from experiments performed at ambient temperature at a strain rate of s–1. Validation criteria based on the Mo experiments may include comparing the stress-strain response using 3-D strain information, the predicted slip-system yield, and work-hardening behavior.
Metallic Island Coalescence: Molecular Dynamics Simulations of Boundary Formation and Tensile Strain in Polycrystalline Thin Films
Authors: Takahashi Andrew R. , Thompson Carl V. , Carter W. Craig 
Published: June 2019

AbstractIsland coalescence during the early stages of polycrystalline film formation is thought to lead to the large values of tensile stress observed in experiments. Continuum models have been developed which are in semi-quantitative agreement with in-situ experimental observations of stress evolution during coalescence. However, the size of coalescing particles is in the nanometer range, so that atomistic treatments might be expected to more accurately reveal the mechanisms leading to coalescence stresses. We have performed molecular dynamics (MD) computational experiments in which small metallic clusters both in free space and on weakly bound substrates are allowed to coalesce. These atomistic simulations complement the finite element modeling (FEM) and analytical work on the tensile strains developed during grain boundary formation by coalescence. Additionally, the atomistic simulations implicitly capture the effects of anisotropy and special orientations. The MD simulations also provide atomic-level detail of the boundary structure that is absent in continuum models. We have focused on simulations of Ag as a high mobility material at and above room temperature and have begun studying Ni as a material that can behave either as a high or low mobility material depending on the deposition temperature(i.e. Ni has a higher activation energy for adatom motion than Ag.). We find that for small islands, the initial boundary formation occurs in times on the order of nanoseconds. For nanometer-sized clusters in free space and on traction-free substrates, the cluster can undergo large rotations prior to boundary formation. The simulated boundary heights fit well with both a FEM model and an analytical model. Work is ongoing to further quantify the results of the simulations and relate the atomistic forces and positions to the stress state. We are pursuing methods for including the effects of traction at the interface, both through continuum and discrete methods.
Grain Rotations during Tensile Deformation of Columnar Tantalum
Authors: El-Dasher B.S. , Adams B. L. , Rollett A. D. 
Published: June 2019

AbstractWe report on tensile tests performed on thin sheet samples of tantalum that have a nearcolumnar structure. By annealing sheet of approximately 1 mm thickness at high temperatures, a columnar structure is generated with grain boundaries nearly perpendicular to the flat surfaces. The purpose of the experiments is to investigate the mechanical behavior in terms of crystal plasticity in a geometry that is readily amenable to both experimental characterization and computer simulation. Automated electron backscatter diffraction (EBSD) has been used to obtain orientation maps both before and after deformation. For the small strains used in this study (<10%), the grains deform rather uniformly with little evidence of cell formation. Analysis of the lattice rotations shows considerable scatter in the rotation axis and demonstrates significant disagreement with polycrystal plasticity calculations.
Aerosol Deposition Method (ADM) for Nano-Crystal Ceramics Coating Without Firing
Authors: Akedo Jun , Lebedev Maxim , Iwata Atsushi , Ogiso Hisato , Nakano Shizuka 
Published: June 2019

AbstractAerosol deposition method (ADM) for shock-consolidation of fine ceramics powder to form dense and hard layers is reported. Submicron ceramic particles were accelerated by gas flow in the nozzle up to velocity of several hundred m/s. During interaction with substrate, these particles formed thick (10 ∼ 100 μm), dense, uniform and hard ceramics layers. Experiments were fulfilled at room temperature. The results of fabrications, microstructure and mechanical properties of oxides (Al2O3; (Ni,Zn)Fe2O3; Pb(Zr0.52,Ti0.48)O3 and non-oxide (AlN; MgB2) materials are presented. Every layer has polycrystalline structure with nano-meter order scale.
Non-Stick and Scratch Resistant Sol-Gel Coating for Aluminum
Authors: Wu Linda Y.L. , Nemeth Sandor 
Published: June 2019

AbstractPTFE-based coatings have been widely used, for example, on aluminum molds for molding of polyolefin packaging materials for its non-stick property. However, these coatings do not meet the users' scratch resistance and durability requirements. This paper describes a preliminary study on the synthesis and characterization of a PTFE/sol-gel composite coating material which combines the required non-stick and low friction properties of PTFE filler with the high scratch resistance and durability of a silica-based sol-gel matrix. The non-stick and low friction properties were achieved by using both the PTFE filler and the lubricious compound resulting from the reaction of a solvent with siloxane. The high scratch resistance was attributed to the enhanced adhesion to the electro-chemically pre-treated surface and the optimized silica and alumina filler contents in the sol-gel material. FE-SEM/EDX, FTIR, contact angle goniometry, scratch testing and a pin-on-disc tribometry were used to evaluate the coating properties.
Surface Analysis of the Environmental Corrosion of Zinalco (Zn-22Al-2Cu) Alloy
Authors: Guerrero-Penalv R. , Farías M.H. , Cota-Araiza L. 
Published: June 2019

AbstractThe surface of a set of zinalco (Zn-22Al-2Cu) samples was prepared by mechanical polishing (MP) and by electropolishing (EP). Samples were subjected to environmental corrosion during 56 days and studied by x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Differences in relative atomic concentration ratio of Al/Zn in oxides of the surface layer were obtained and they are related to the bulk microstructure. A different corrosion behavior is observed between MP and EP samples and it is explained in terms of surface composition and morphology. The initial growth of corrosion products was observed in EP samples and a corrosion model is proposed. The surface of both types of samples can be modified by lowenergy argon ion bombardment.
The Effect of Ag Addition on the Corrosion of Zn-22wt%Al Alloys
Authors: M. Flores , L. Huerta , S. R. Casolco , S. Muhl , G. Torres-Villaseñor , J.A. Luna 
Published: June 2019

AbstractA new Zn–Al-Ag alloy (ZINAG) with mechanical superplastic properties has been developed. In this work four of the Zn–22wt%Al eutectoid alloy doped with between 0.5 to 4.24 wt% Ag have been studied. The superplastic behavior can be explained as a consequence of the fine grain distribution induced during the deformation process. Here the corrosion resistance of these alloys was studied by means of potentiodynamic polarization and measurements of the temporal evolution of the corrosion potential, in a 0.5 M NaCl solution. The corrosion products in the sample surface were analyzed by Rutherford Backscattering Spectrometry (RBS), X-Ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES). It was found that the corroded surface had lost more Zn than Al. The surface was examined by SEM and it was seen that the corrosion products adhered to the surface cracks. It was found that the alloy with 2.12 wt% concentration of Ag had the best corrosion resistance in the electrolyte used, but no clear tendency with the Ag concentration was found.
Photo-Induced Corrosion in Microelectronic Devices Containing Dissimilar Metals.
Authors: Belisle C. , Westergard L. , Florence D. , Haskett T. , Scott G. , Greenwood B. , Prasad J. , Engle M. 
Published: June 2019

AbstractVarious metals with different galvanic potentials are used to fabricate the microelectronic circuits. One of the most commonly used processes during integrated circuit manufacturing is the tungsten via fill. To obtain maximum interconnect density with low via resistance requires that metal-via overlap is essentially zero. Zero overlap with litho variations and thus misalignment may result in unlanded vias. Since the vias are used to connect various metal levels, a large number of these cases may occur causing device failures and thus yield loss. To study this problem a variety of test structures were studied and a new mechanism of corrosion was found. The tungsten corrosion observed in these structures was found to be photo-induced. In this paper we will discuss the mechanism of photoinduced galvanic corrosion that occurs between the aluminum and tungsten metal layers during microelectronic manufacturing.
Real time in-situ stress evolution investigation of highly textured electrodeposited bismuth thin films
Authors: Fan Donglei , Zhu Frank Q. , Shao Ingrid X. , Searson P. C. , Cammarata R. C. 
Published: June 2019

AbstractBismuth, a semi-metal with very long mean free path and large magnetoresistance (MR) effect, is a novel candidate material for thin film spintronic devices. Electrochemical deposition followed by a post-deposition anneal has resulted in highly textured bismuth films as characterized by x-ray diffractometry and pole figure measurements. A highly sensitive, real time in-situ stress measurement system was designed and employed to study stress generation during bismuth film growth. Bismuth films displayed a monotonically increasing compressive stress during deposition. The magnitude of the compressive stress decreased with the deposition rate in the range 1.5 Å/sec to 50 Å/sec.
Low Substrate Temperature Deposition of Crystalline SiC using HWCVD
Authors: Klein S. , Carius R. , Houben L. , Finger F. 
Published: June 2019

AbstractMicrocrystalline silicon carbide (μc-SiC) was prepared at substrate temperatures between 300°C and 450°C using Hot Wire Chemical Vapour Deposition (HWCVD). The SiC films were deposited from monomethylsilane (MMS) diluted in hydrogen on glass and crystalline silicon substrates. The influence of the hydrogen dilution on the deposition rate and the structural and the optoelectronic properties was investigated. Infrared and Raman spectroscopy and transmission electron microscopy (TEM) were applied to study the structural properties. Highly crystalline material with large columnar grains was obtained at high hydrogen dilutions. The optical absorption below the band gap is high and the dark conductivities are far above the values expected for intrinsic SiC. At lower hydrogen dilution, less crystalline or amorphous Si1-xCx is growing, showing broader IR- and Raman peaks, lower dark conductivity and higher absorption above the band gap energy. An extended nucleation zone with large structural disorder was observed even for highly crystalline material.
Improved Stability of Hydrogenated Amorphous Silicon Solar Cells Fabricated by Triode-Plasma CVD
Authors: Sonobe H. , Sato A. , Fujibayashi T. , Shimizu S. , Matsui T. , Matsuda A. , Kondo M. 
Published: June 2019

AbstractWe have employed a triode-type plasma CVD system to fabricate highly stabilized hydrogenated amorphous silicon (a-Si:H) solar cells. The p-i-n type solar cells were fabricated on a textured SnO2/glass substrate (ASAHI VU type). By applying a triode system, the Si-H2 bond density in the film decreased to about one third (from 1.7 at.% for conventional parallel-plate-electrode to 0.6 at.% for a triode configuration), and correspondingly the degradation ratio decreased from 13 % to 10 %. We have achieved the degradation ratio of 5 % by optimizing the player deposition conditions. In case of a triode system, there were minor effects of higher hydrogen dilution in the stabilized efficiency. We have experimented the effects of the substrate temperature for a higher stabilized efficiency. Further improvement in solar efficiency has been made by applying antireflection layers to air/glass and TCO/p interfaces. As a result, we have achieved the stabilized efficiency of 9.22 % (Jsc = 15.9 mA/cm2, Voc = 0.863 V, FF = 0.672) with a degradation ratio of 7.8 %. We have also employed the triode-deposited a-Si:H solar cell to a tandem type solar cell with a structure of a-Si:H/hydrogenated microcrystalline silicon (μc-Si:H). We have achieved the stabilized efficiency of 10.9 % (Jsc = 12.0 mA/cm2, Voc = 1.31 V, FF = 0.691) with a degradation ratio of 7.3 %.
Correlation between Powder in the Plasma and Stability of High Rate Deposited a-Si:H
Authors: Yue Guozhen , Ganguly Gautam , Yan Baojie , Yang Jeffrey , Guha Subhendu 
Published: June 2019

AbstractHydrogenated amorphous silicon (a-Si:H) solar cells incorporating high deposition rate (8-10Å/s) intrinsic layers were deposited using modified very high frequency (MVHF) plasma. We have monitored the light scattered from powder generated in the plasma using an Ar-laser and a silicon photodiode. This simple, non-invasive technique allows us to make measurements on the same reactor used to make the solar cells. First, we have varied the total flow rate and observed a maximum in the scattered light intensity from powder in the plasma during the deposition of the intrinsic layer, and correlated this with the degradation, as well as the stabilized performance of the solar cells. Then, we have studied the effects of varying the deposition temperature and/or the addition of germane to the gas mixture on the scattered light intensity due to powder in the plasma.
Application of Spectroscopic Ellipsometry and Infrared Spectroscopy for the Real-Time Control and Characterization of a-Si:H Growth in a-Si:H/c-Si Heterojunction Solar Cells
Authors: Fujiwara Hiroyuki , Kondo Michio 
Published: June 2019

AbstractWe have demonstrated real-time process control of a-Si:H growth in an a-Si:H/c-Si heterojunction solar cell by spectroscopic ellipsometry (SE). Accurate thickness control of a-Si:H p-i layers with a precision better than ± Å has been realized by this technique. From real-time attenuated total reflection spectroscopy (ATR), we find the formation of a porous interface layer with a maximum SiH2-hydrogen content of 27 at.% at the a-Si:H/c-Si interface, although a rather high conversion efficiency of 14.6 % has been obtained in the solar cell. We found that an optimum i-layer thickness for the a-Si:H/c-Si solar cells is consistent with the thickness at which the a-Si:H i-layer growth reaches a steady state after the H-rich interface-layer formation. We have applied SE further to determine the dielectric functions of In2O3:Sn and ZnO:Ga with different carrier concentrations. From the dielectric function analysis, the effective mass m is extracted. We find linear increases in m as the carrier concentration of In2O3:Sn and ZnO:Ga increases. The validity of our analyses has been confirmed from excellent agreement between carrier concentrations determined by SE and Hall measurements. The construction of the optical database further enabled us to calculate a reflectance spectrum of the a-Si:H/c-Si solar cell accurately.
Novel in situ and real-time optical probes to detect (surface) defect states of a-Si:H
Authors: Kessels W.M.M. , Aarts I.M.P. , Gielis J.J.H. , Hoefnagels J.P.M. , van de Sanden M.C.M. 
Published: June 2019

AbstractThis paper describes two novel optical diagnostics that were recently introduced to the field of Si-based thin films, in particular for probing defect states present in the bulk and at the surface of a-Si:H films. It is expected that these diagnostics, when applied in situ or real time during film growth, can provide new insights into the a-Si:H film properties as well as into the fundamental surface processes during growth. The first method is cavity ringdown spectroscopy (CRDS). From ex situ measurements on a-Si:H thin films, it is shown that this method is very powerful for measuring absolute defect-related absorptions at subgap energies without the need for a calibration procedure, even for films as thin as 4 nm. It is also shown that the method can be used for measuring rare-earth dopants – here Er3+ in silicon-rich oxide – to the extent that issues about absorption cross-sections can be resolved by using thin samples instead of waveguides. Furthermore, the in situ application of the method for thin films is discussed by presenting the evanescent-wave cavity ringdown (EW-CRDS) technique. The second method is spectroscopic second harmonic generation (SHG). It has been found that this non-linear optical technique yields a photon energy dependent signal for as-deposited a-Si:H films and that this signal has a contribution from a-Si:H surface states. From a comparison with c-Si surface science studies, the possible origin of the signal from surface Si dangling bonds and strained Si-Si bonds is discussed. The application of SHG during real-time film growth is also presented.
Computer Modelling of Non-Equilibrium Multiple-Trapping and Hopping Transport in Amorphous Semiconductors
Authors: Main C. , Marshall J. M. , Reynolds S. , Rose M.J. , Brüggemann R. 
Published: June 2019

AbstractIn this paper we demonstrate a simple computational procedure for the simulation of transport in a disordered semiconductor in which both multi-trapping and hopping processes are occurring simultaneously. We base the simulation on earlier work on hopping transport, which used a Monte-Carlo method. Using the same model concepts, we now employ a stochastic matrix approach to speed computation, and include also multi-trapping transitions between localised and extended states. We use the simulation to study the relative contributions of extended state conduction (with multi-trapping) and hopping conduction (via localised states) to transient photocurrents, for various distributions of localised gap states, and as a function of temperature. The implications of our findings for the interpretation of transient photocurrents are examined.