bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Interfaces on the Phase Stability in Nanostructured Thin Film Multilayers
Authors: Thompson G.B. , Banerjee R. , Dregia S.A. , Fraser H.L. 
Published: June 2019

AbstractNanostructured thin film multilayers, comprising of alternating A/B layers, can exhibit metastable structures in one or both layers. From a classical thermodynamic viewpoint, the reduction interfacial energy is primarily responsible for this stabilizing effect. Based on this idea, a model has been constructed in which phase stability regions are represented as functions of both the bilayer thickness and volume fraction of the one the layers. Applying this classical thermodynamic model to a single, previously reported hcp to bcc transformation in Zr for Zr/Nb multilayers, a phase stability diagram was proposed. Various Zr/Nb multilayers with different bilayer thicknesses and volume fractions have been sputtered deposited. hcp to bcc transformations in the Zr layer were confirmed by x-ray and electron diffraction. Furthermore the Zr/Nb stability diagram predicted a novel hcp Nb phase which was subsequently verified experimentally. Using Zr/Nb as a guide, a similar phase stability diagram was constructed and experimentally determined for Ti/Nb multilayers. For each multilayer system, the reduction in interfacial energy was calculated from the experimentally determined diagram. These values were then compared to estimations of the structural component of the interfacial energy. The structural component was based on the energy per unit area of a misfit dislocation network constructed by an o-lattice. This simple assesment suggests that the reduction of the structural component of the interfacial energy is sufficient to drive the transformation.
Quantitative High-Resolution Transmission Electron Microscopy of III-V Semiconductor Interfaces by Multivariate Statistical Analysis of Exit-Plane Wave Function Images
Authors: Mahalingam Krishnamurthy , Eyink Kurt G. , Brown Gail J. , Dorsey Donald L. 
Published: June 2019

AbstractThe application of exit-plane wave function (EPWF) images for an atomic-scale compositional mapping of interfaces in the GaAs-AlAs system is investigated. Image simulations based on the multislice algorithm were performed to obtain EPWF images over a wide range of compositions and specimen thicknesses. The EPWF-amplitude images were further analyzed by the method of factorial analysis of correspondence. A simultaneous analysis of the effects both thickness and composition on image contrast yielded two eigenvectors representing the individual contributions from the two effects. This separation was however not complete, leaving a residual contribution from thickness on the composition-sensitive eigenvector and vice versa. Extraction of the chemical content from the composition-sensitive eigenvector is still possible by a parameterization of the residual thickness contribution. A simpler procedure for quantifying the composition across an interface is proposed based on the analysis of images of AlxGa(1-x)As with different Al/Ga composition but same specimen thickness.
Closed-Cell Mesostructured Porous Silica Films Templated by PS-b-PEO Without Additional Microporosity
Authors: Yu Kui , Smarsly Bernd , Brinker Jeffrey 
Published: June 2019

AbstractMesostructured silica/diblock films with a 3D arrangement of spherical domains (bcc) were prepared through evaporation-induced self-assembly (EISA) using polystyrene-blockpoly( ethylene oxide) diblock copolymers as structure-directing agents and TEOS (Si(OCH2CH3)4) and/or MTES (Si(OCH2CH3)3CH3) as silica precursors. A detailed small angle x-ray scattering (SAXS) analysis of the calcined mesoporous films showed that, in contrast to recently reported studies, no additional microporosity due to the PEO was observed, indicating that the PEO block formed a layer at the interface between the PS domain and the silica matrix and thus contributed to the mesopore volume. These mesostructured porous silica films are believed to be the first in respect of isolated spheres with a 3D array distributed in a silica matrix without additional microporosity and with MTES as silica precursor. Such closed-cell mesostructured porous materials with high porosity and controllable hydrophobicity can be excellent candidates for low dielectric (K) insulator materials.
Plasmon Scanned Surface-Enhanced Raman Scattering Excitation Profiles
Authors: Haynes Christy L. , Van Duyne Richard P. 
Published: June 2019

AbstractSince the discovery of surface-enhanced Raman spectroscopy (SERS) in 1977, scientists have come to understand the enhancement mechanism, but have been unable to consistently optimize the weak signals inherent in Raman experiments. Surface-enhanced Raman signals originate from excitation of the localized surface plasmon resonance (LSPR) of a nanostructured metal surface, thus producing concentrated electromagnetic fields at the surface of the nanostructure. Design of the nanostructured metal substrate plays an important role in understanding and optimizing SERS experiments. In this research, the size-dependent optical properties accessible by nanosphere lithography (NSL) are exploited to fabricate topographically predictable SERS-active substrates with systematically varying LSPRs. Correlated microextinction and micro-Raman measurements, as well as quantitative implementation of a Raman standard, allow significant improvements over the current method used to optimize SERS experiments. The knowledge gained in the novel plasmon scanned SERS excitation profiles clearly indicates the substrate parameters necessary for experimental optimization and promotes further understanding of the SERS enhancement mechanism.
Electrochromic WO3-x and Colossal Magnetoresistive (La, Sr)MnO3 Perovskite Oxide Thin Films by Pulsed Laser Deposition
Authors: Mitsugi Fumiaki , Hiraiwa Eiichi , Ikegami Tomoaki , Ebihara Kenji , Suda Yoshiaki 
Published: June 2019

AbstractThe functional oxide thin films of electrochromic WO3-x and colossal magnetoresistive La0.8Sr0.2MnO3 were prepared by a KrF excimer pulsed laser deposition technique. Optical transparency and electrical conductivity of the WO3-x film were changed by the oxygen content in the lattice. Triclinic, tetragonal and amorphous WO3-x films were prepared by adjusting the oxygen atmosphere during the deposition. We revealed the relationship between the crystal structure and the gas sensing property of the films. The triclinic WO3-x film (1 μm) showed the high sensitivity to NO (60 ppm) gas at an operating temperature of 150°C. The colossal magnetoresistive La0.8Sr0.2MnO3 thin film having the MR ratio of 15 % (H=7 kG) was deposited under the conditions of the laser energy density of 2 J/cm2 (5Hz), substrate temperature of 850°C and oxygen pressure of 500 mTorr. The magnetic sensor composing of the La0.8Sr0.2MnO3 thin film responded to the AC magnetic field (1 kHz).
Formation of Nanometer-Scale Dot Arrays from Diblock Copolymer Templates
Authors: Black C. T. , Guarini K. W. , Sandstrom R. L. , Yeung S. , Zhang Y. 
Published: June 2019

AbstractWe have developed four different fabrication processes based on self-organizing diblock copolymers that all produce densely-spaced, uniformly-sized nanometer-scale dot arrays over large wafer areas. We demonstrate the versatility of these techniques through examples of dot arrays formed of metallic, insulating, and polymeric materials. These fabrication processes vary in complexity, utility, and degree of optimization, and we discuss the relative merits of each. The ability to create uniform nanoscale features below lithographic resolution limits may enable key applications in fields such as magnetic recording and microelectronics.
Laser Oscillation in Aggregates of Ultrasmall Si Nanoparticles
Authors: Nayfeh Munir H. 
Published: June 2019

AbstractWe dispersed electrochemically etched Si into ultrabright ultrasmall nanoparticles, with brightness higher than fluorescein or rhodamine. The emission from single particles is readily detectable. Aggregates or films of the particles exhibit emission with highly nonlinear characteristics. We observe directed blue beams at ∼ 410 nm between faces of aggregates excited by femtosecond radiation at 780 nm; and at ∼ 610 nm from aggregates of red luminescent Si nanoparticles excited by radiation at 550-570 nm from a mercury lamp. Intense directed Gaussian beams, a pumping threshold, spectral line narrowing, and speckle patterns manifest the emission. The results are analyzed in terms of population inversion and stimulated emission in quantum confinement-induced Si-Si dimer phase, found only on ultrasmall Si nanoparticles. This microlasing constitutes an important step towards the realization of a laser on a chip.
Investigations of Substrate-Selective Covalent Attachment for Genetically-Engineered Molecular Interconnects
Authors: Rana N. , Bousman K. , Shekhawat G. S. , Sirinakis G. , Heuchling F. , Welch J. , Eisenbraun E. T. , Geer R. E. , Kaloyeros A. E. 
Published: June 2019

AbstractExperimental investigations are presented regarding the surface-selective molecular selfassembly of fluorinated monochloroalkylsilane of the type (heptadecafluoro-1,1,2,2-tetrahydrodecyl) dimethylchlorosilane (denoted F17) on silicon dioxide (SiO2) and silicon nitride (Si3N4) surfaces. The goal is to investigate the controlled and selective surface self-assembly of these molecules as a potential route for substrate-selective covalent bonding of complex molecular assemblies to semiconductor substrates for on-chip interconnect and device applications. X-ray photoelectron spectroscopy (XPS), x-ray reflectivity (XRR) and atomic force microscopy (AFM) have been used to investigate the selectivity of the F17 self-assembly. Contrary to previous reported results, a high degree of F17 monolayer attachment selectivity is consistently observed between SiO2 and Si3N4 substrates for all three of the aforementioned monolayer characterization methods.
Study of Field Emission Behavior of Carbon Nanotubes with Different Sources
Authors: Lin Mark Ching-Cheng , Lai M.S. , Lai H. J. , Yang M. H. , Wei B.Y. , Li A. K. 
Published: June 2019

AbstractThe field emission properties of carbon nanotubes (CNTs) from various sources are investigated for the application of field emission displays. Comparisons are made between graphite with Ni metal as catalyst and polycyclic aromatic hydrocarbon as precursor by the arc discharge method. Cathode deposits are examined using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) to determine microstructure. Carbon structure is studied using Raman spectroscopy. Electron field emission characteristics are measured with the diode method at 10-6 torr pressure. In this study, SEM micrographs of cathode deposits show dense random fiber-like carbon nanotubes. The HRTEM images clearly exhibit characteristic features of multiwalled carbon nanotubes. Microstructural investigation provides evidence that both the metal catalyst and the precursor can be used to synthesize carbon nanotubes. The Raman spectrum shows a stronger peak at about 1580 cm-1 indicating formation of a well-graphitized carbon nanotube. The degree of carbon nanotube graphitization is high and is in good agreement with the HRTEM result. From field emission measurements, the lowest onset field is about 1.0 V/μm and can be attributed to highly sharp tips and the high density of carbon nanotubes. Based on microstructure characterization and field emission measurements, the influence on field emission properties including turn on voltage and threshold voltage of carbon nanotubes synthesized from different sources is discussed.
Development of “New Abrasive-Free Copper CMP Solutions” BASED on Electrochemical and Film Analysis Method
Authors: Amanokura Jin , Kamigata Yasuo , Habiro Masanobu , Suzuki Hiroshi , Hanazono Masanobu 
Published: June 2019

AbstractAbrasive-free Cu CMP solutions have been developed to reduce micro-scratches and obtain minimized dishing and erosion properties. During the development of the solutions, some electrochemical examinations were performed. One of the most instructive knowledge was obtained through the Tafel plot. Other attractive data were obtained through Cu complex film analysis. On the basis of these studies were developed and released newly formulated abrasive-free Cu CMP solutions with a high Cu removal rate and excellent topography performance. Mechanism of polishing by applying abrasive-free Cu CMP solutions is also discussed in this paper.
Topography Reduction During Barrier CMP Improved Due to Tantalum Oxidation
Authors: Lefevre Paul , Ina Katsuyoshi , Sakai Kenji , Tamai Kazusei , Rader Scott 
Published: June 2019

AbstractBarrier CMP can reduce the topography generated during Cu CMP. In case of selective barrier CMP slurry like 1:10:1, it is expected that the topography reduction could not exceed the Ta thickness. Some recent observations made at Fujimi show that the topography reduction can be twice larger than the Ta thickness without dielectric loss. This paper presents the chemical mechanical phenomenon that is responsible for this 40 to 50 nm topography reduction during barrier CMP. At the end of the Cu CMP, Ta is exposed to oxidizer. This process can oxidize an important part of the Ta barrier which becomes Ta2O5 according to Pourbaix diagram [1]. Ta2O5 can be as much as 2.3X thicker than original Ta layer. This phenomenon explains why topography reduction can be twice higher than initial Ta thickness. This mechanism explains why after Cu CMP it is likely to have more than 30 nm dishing on copper lines. The last and more important consequence is that this reduces final topography and total copper metal loss at the same time by about 30 nm. Obviously very high selectivity Cu CMP slurry (Cu:Ta ∼ 1000:1) is necessary to have neither Ta erosion nor Ta2O5 erosion during copper CMP. High selectivity slurry is required during barrier CMP in order to reduce the loss of copper and Dielectric during Barrier CMP.
Pad Conditioning and Pad Surface Characterization in Oxide Chemical Mechanical Polishing
Authors: Lawing A. Scott 
Published: June 2019

AbstractAn understanding of the pad surface state and its effect on the polishing process is critical to a more fundamental understanding of Chemical Mechanical Polishing (CMP). Vertical Scanning Interferometry has been shown to be a useful tool to monitor the pad surface state. In this paper, various techniques for analyzing pad surface data obtained using interferometry are described. The pad surface state can be modified through the manipulation of process and pad conditioner design parameters. Many of the parameters extracted from interferometry data show strong correlations with corresponding polish data. A careful analysis of these complementary data can yield significant insight into the mechanisms of CMP processes.
Effect of Temperature and Temperature Uniformity on Plasma and Device Stability
Authors: Ganguly G. , Bennett M.S. , Carlson D.E. , Arya R.R. 
Published: June 2019

AbstractWe have investigated the changes in the cathode potential in a dc discharge of silane and hydrogen used to deposit the intrinsic layer of p-i-n type solar cells at deposition rates from 1 to 10Å/s with the superstrate temperature at 200°C and 250°C. Under plasma conditions that lead to higher deposition rates (5-10Å/s), fluctuations of the cathode potential which are suggestive of the formation and de-trapping of particulates in/from the plasma, are observed at 200°C but disappear at 250°C. Improvement of the temperature uniformity over the plasma region from 1.7°C/cm to 0.7°C/cm removes the fluctuations of the cathode potential even at 200°C, indicating that the particulates are formed predominantly at the plasma boundary. Consequently, the stability of solar cells with i-layers deposited at ~10Å/s in the center of the plasma region at the same superstrate temperature improved by 26% suggesting that multiple silicon containing molecules diffuse from the edge to the center of the plasma region.
Temperature Dependence of a Hydrogen Doublet Site in Light-Soaked a-Si:H From 1H NMR
Authors: Su T. , Taylor P. C. , Ganguly G. , Carlson D. E. 
Published: June 2019

AbstractWe investigate the temperature dependence of an additional 1H NMR signal that appears in aSi:H at T = 7 K only after light soaking. This “doublet” signal is attributed to a pair of hydrogen atoms approximately 2.3 Å apart. We present the first lineshape of this doublet, and we examine the spin-lattice relaxation from 6.5 K to 20 K at a magnetic field of about 3.5 T. At low temperatures, the spin-lattice relaxation time of these paired hydrogen sites has a strong dependence on temperature, which is probably the result of some form of local motion.
Towards Microcrystalline Silicon n-i-p Solar Cells with 10% Conversion Efficiency
Authors: Feitknecht L. , Droz C. , Bailat J. , Niquille X. , Guillet J. , Shah A. 
Published: June 2019

AbstractHigh-performance microcrystalline and amorphous silicon solar cells are the key elements for a successful combination to form the “micromorph” tandem cell [1,2]. A microcrystalline silicon (μc-Si:H) solar cell in the n-i-p configuration was fabricated by the VHF PE-CVD deposition process. The cell has a conversion efficiency exceeding 9% (VOC=520 mV, FF=73%, JSC=24.2 mA/cm2). This result was achieved by a successful combination of the following elements: first a fine-tuning of the silane concentration (SC) in hydrogen feedstock gas used for deposition of the intrinsic <i> absorber layer, second, the incorporation of an optimised back-reflecting substrate into the cell; and, third, the ideal combination of each of these key-components.Compared to earlier results with n-i-p-type μc-Si:H solar cells, a substantial increase in VOC was now obtained, while maintaining reasonable JSC-values. Earlier investigations on the role of the i-layer material had revealed a trade-off between cells with high JSC but low VOC or cells of low JSC and high VOC. In the present contribution the authors now show the successful combination of a cell with an acceptable VOC and good JSC generation in the long-wavelength region (above 700 nm). This is mainly because of suitable light-diffusing back-reflectors which perform well with respect to both, optical and electrical aspects.
Influence of Laser Annealing on Hydrogen Bonding in Disordered Silicon Thin Films
Authors: Nickel N. H. , Brendel K. 
Published: June 2019

AbstractThe influence of laser dehydrogenation and crystallization of hydrogenated amorphous silicon (a-Si:H) on H bonding is investigated. Depending on the deposition temperature the amorphous starting material contains a H concentration of up to 44 at.%. Laser crystallization lowers the H content significantly. Fully crystallized poly-Si contains H concentrations of up to 17 at.%. This reservoir of hydrogen can be used to passivate additional grain boundary defects by annealing the specimens at low temperatures in vacuum. Information on hydrogen bonding is obtained from hydrogen effusion measurements.
Light and Thermally Induced Metastabilities in Nanocrystalline Silicon
Authors: Mandal N. P. , Agarwal S. C. 
Published: June 2019

AbstractLight soaking for short durations and thermal quenching produce metastable states having a higher dark current, higher photo current, a larger photoluminescence and a smaller electron spin resonance signal in porous silicon (PS). Long exposures, however, have the opposite effect. All metastabilities can be removed by annealing at 150°C (1 h), but not by exposure to infrared light. Micro-Raman spectroscopy shows the presence of a-Si:H in the PS sample. However, a closer look shows that our results can not be explained in terms of a-Si:H alone. Our experiments suggest that structural changes involving the movement of hydrogen present on the surface of PS or on PS/a-Si:H interface may be responsible for these effects.
Correlation Between the Tunnelling Oxide and I-V Curves of MIS Photodiodes
Authors: Águas H. , Pereira L. , Goullet A. , Silva R. , Fortunato E. , Martins R. 
Published: June 2019

AbstractIn this work we present results of a study performed on MIS diodes with the following structure: substrate (glass) / Cr (2000Å) / a-Si:H n+ (400Å) / a-Si:H i (5500Å) / oxide (0-40Å) / Au (100Å) to determine the influence of the oxide passivation layer grown by different techniques on the electrical performance of MIS devices. The results achieved show that the diodes with oxides grown using hydrogen peroxide present higher rectification factor (2×106)and signal to noise (S/N) ratio (1×107 at -1V) than the diodes with oxides obtained by the evaporation of SiO2, or by the chemical deposition of SiO2 by plasma of HMDSO (hexamethyldisiloxane), but in the case of deposited oxides, the breakdown voltage is higher, 30V instead of 3-10 V for grown oxides. The ideal oxide thickness, determined by spectroscopic ellipsometry, is dependent on the method used to grow the oxide layer and is in the range between 6 and 20 Å. The reason for this variation is related to the degree of compactation of the oxide produced, which is not relevant for applications of the diodes in the range of ± 1V, but is relevant when high breakdown voltages are required.
Numerical Simulation of the Influence of the Gap State of a-Si:H on the Characteristics of a-Si:H p-i-n/OLED Coupling Device
Authors: Wu Chunya , Chen Yousu , Li Juan , Yang Guanghua , Yang Huidong , Zhou Zhenhua , Zhao Ying , Meng Zhiguo , Geng Xinhua , Xiong Shaozheng , Zhang Lizhu , Wang Qi 
Published: June 2019

AbstractThe influence of the density of gap states and the band gap width of the intrinsic a-Si:H active layer on the characteristics of a-Si PIN/OLED coupling pair was analyzed by a-Si:H PIN/OLED CAD simulation model. The CAD simulation model was carried out based on a-Si PIN Hack & Shur model and OLED TCL transport model. At the same band gap width, for the intrinsic a-Si:H active layer with the higher density of gap states, the reverse current of a-Si PIN trended to be saturated at the higher reverse bias voltage. As a result, I-V curve of a-Si PIN/OLED around the turn point Vt became smoother with the increase of the density of gap states. At the same state density, the light induced current of a-Si PIN increased against the band gap width, assuming the input light had the same spectrum as AM1.5 solar light. Thus the luminance emitted from OLED increased with the decrease of the band gap width because OLED belongs to the light-emitting device controlled by current. The simulation results also showed that the influence of the state density intensified with the increase of the band gap of a-Si:H.
Area-Dependent Switching in Thin Film-Silicon Devices
Authors: Hu Jian , Jackson Warren , Ward Scott , Stradins Pauls , Branz Howard M. , Wang Qi 
Published: June 2019

AbstractWe report on the area dependence of switching in both Cr/p+a-Si:H/Ag(Al) and Cr/p+μc-Si/Ag(Al) filament switches. The doped amorphous (a-Si:H) or microcrystalline (μc-Si) thin Si layers are made by hot-wire chemical vapor deposition. The device active region area (A) is varied over 5 orders of magnitude, from 10-7 to 10-2 cm2, using photolithographically defined Ag and Al top contacts. Before switching, the resistance of 100-μm2 devices is normally about 100 kΩ for μc-Si and 10 GΩ for a-Si:H. After switching with applied current ramps, the resistance decreases to a few hundred ohms in all a-Si devices and to a few thousands ohms in μc-Si devices. In both μc-Si and a-Si:H devices, the switching voltage (Vsw) decreases with increasing device area according to Vsw ~ V0-αln(A/A0) with α=0.3V for a-Si:H and α=0.04V for μc-Si. For both materials, the switching current roughly obeys the power law Isw ∞ Aβ with β~1. A statistical model is proposed to explain the area scaling of the switching voltage and relate the parameters to the material properties.