bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrodeposition of Metals on Conductive Polymer Films
Authors: Hepel Maria , Adams Laura , Rice-Belrose Cynthia
Published: June 2019

The electrodeposition of copper on composite conductive polymer polypyrrole/polystyrenesulfonate PPy(PSS) has been studied. The morphology of copper deposits was investigated in the presence of thiourea and other additives. It has been found that in the presence of thiourea in the solution, the rate of copper deposition on a PPy(PSS) substrate is slightly inhibited but the rate of copper stripping is faster than in its absence. The Electrochemical Quartz Crystal Microbalance (EQCM) technique allowed us to simultaneously monitor voltamperometric and resonance frequency vs. potential or time characteristics. The amount of electrodeposited copper was controlled by monitoring the EQCM resonant frequency. Composite PPy(PSS) films functioning as cation-exchange membranes were used as substrate materials for metal deposition. They allowed us to electrodeposit copper not only on the surface of the conductive polymer but also inside the polymer matrix. The size of copper nanocrystals formed inside the polymer was controlled by the applied electrode potential. Copper crystals as small as 20 nm were detected with Transmission Electron Microscopy (TEM).
Open Air Fabrication of Al2O3 Thin Films at Room Temperature
Authors: Okamoto T. , Toyoda K. , Murahara M.
Published: June 2019

A thin layer of water or hydrogen peroxide solution, which was formed on a pure aluminum substrate, was photodissociated by ArF excimer laser( λ =193nm) or Xe2* excimer lamp (λ = 172nm) light to photochemically oxidize the surface of aluminum substrate. The layer was formed by a capillary phenomenon between the substrate and a fused silica glass as an entrance window of ultraviolet light. Then, the layer was photodissociated by the excimer laser or the excimer lamp light irradiation to generate active oxygen; the surface oxidization was performed by the photo-induced active oxygen. The surface before and after modification was evaluated by the XPS analysis; the high densed photo-oxidization film was confirmed on the modified surface, compared with a natural oxidization film Furthermore, the contact angle with water became remarkably small, and it is seen that the treated surface was quite densely oxidized.
Halide Electroadsorption on Single Crystal Surfaces
Authors: Ocko B. M. , Wandlowski Th.
Published: June 2019

The structure and phase behavior of halides have been investigated on single crystals of Ag and Au using synchrotron x-ray scattering techniques. The adlayer coverages are potential dependent. For all halides studied we found that with increasing potential, at a critical potential, a disordered adlayer transforms into an ordered structure. Often these ordered phases are incommensurate and exhibit potential-dependent lateral separations (electrocom-pression). We have analyzed the electrocompression in terms of a model which includes lateral interactions and partial charge. A continuous compression is not observed for Br on Ag(100). Rather, we find that the adsorption is site-specific (lattice gas) in both the ordered and disordered phases. The coverage increases with increasing potential and at a critical potential the disordered phase transforms to a well-ordered commensurate structure.
Electrochemical Reactions of Molybdenum Nitride Electrodes in H2SO4 Electrolyte
Authors: Roberson S. L. , Finello D. , Davis R. F.
Published: June 2019

The electrochemical reaction of polycrystalline MoxN (x=1 or 2) thin film electrodes in 4.4 M H2SO4 electrolyte has been investigated. The films were prepared by a temperature programmed procedure involving the reaction of MoO3, and NH3 The electrochemical voltage stability of these films in the electrolyte, referenced to a standard hydrogen electrode (SHE), was + 0.70 V (-0.01 to + 0.69). Below + 0.69 V, cyclic voltammetry and AC impedance spectroscopy indicated that MoxN electrodes were capacitive. However, above this value an electrochemical reaction of the MoxN films was observed. The formation of an amorphous phase in the reacted MoxN films was indicated by X-ray diffraction (XRD) patterns. Secondary ion mass spectroscopy (SIMS) detected the presence of hydrogen, oxygen, and sulfur. The voltage bias (+ or -) applied to the electrodes influenced the chemical composition of the reacted MoxN films.
The Effects of Carbonate-Bicarbonate Concentration on Empirical Corrosion Diagram of Mild Steel as a Material of Geological Disposal Package for High Level Nuclear Wastes
Authors: Nakayama Guen , Fukaya Yuichi , Akashi Masatsune
Published: June 2019

In the scheme for geological disposal of high level radioactive nuclear wastes, the burial pit is to be isolated from the sphere of human life by a multiple-barrier system, which consists of an artificial barrier, composed of a canister, an overpack and a bentonite cushioning layer, and a natural barrier, which is essentially the bedrock. As the greatest as well as essentially the sole detriment to its integrity would be corrosion by groundwater. The groundwater comes to it seeping through the bentonite zone, thereby attaining conceivably the pH of transition from general corrosion to passivity, pHd, the behaviors of mild steel in such a groundwater environment have been examined. It has been shown that the pHd is lowered (enlargement of the passivity domain) with rising temperature and carbonate-bicarbonate concentration, while it is raised (enlargement of the general corrosion region) with increasing concentrations of chloride and sulfate ions.
Nanofabricated SiO2-Si-SiO2 Resonant Tunneling Diodes
Authors: Fleming J. G. , Chow E. , Lin S.-Y.
Published: June 2019

Resonance Tunneling Diodes (RTDs) are devices that can demonstrate very highspeed operation. Typically they have been fabricated using epitaxial techniques and materials not consistent with standard commercial integrated circuits. We report here the first demonstration of SiO2-Si-SiO2 RTDs. These new structures were fabricated using novel combinations of silicon integrated circuit processes.
Electronic and Magnetic Properties of d1 Pnictide-Oxides: Na2Ti2Pn2O (Pn = As, Sb)
Authors: Ozawa Tadashi C. , Bieringer Mario , Greedan John E. , Kauzlarich Susan. M.
Published: June 2019

Bulk physical properties of layered pnictide-oxides, Na2Ti2Pn2O (Pn = As, Sb) have been characterized. Both As and Sb compounds exhibit anomalous transitions in temperature dependent magnetic susceptibility and electrical resistivity. The powder neutron diffraction data show no superlattice reflections indicative of long-range order. The origin of the physical property anomalies and structure-property relationship between As and Sb compounds are described in terms of a charge-density-wave/spin-density-wave mechanism.
Electronic, Magnetic and Structural Properties of the RFeO3 Antiferromagnetic-Perovskites at Very High Pressures
Authors: Pasternak Moshe P. , Xu W. M. , Rozenberg G. Kh. , Taylor R. D.
Published: June 2019

At ambient pressure the orthorhombic perovskites R-orthoferrites (R Ξ Lu, Eu, Y, Pr, and La) exhibit very large optical gaps. These large- gap Mott insulators in which the 3d5 high-spin ferric ions carry large local moments and magnetically order at TN > 600 K, undergo a sluggish structural first-order phase transition in the 30-50 GPa range, with the exception of the LuFeO3 which undergoes an isostructural volume reduction resulting from a high to low-spin crossover. High-pressure methods to 170 GPa using Mossbauer spectroscopy, resistance, and synchrotronbased XRD in diamond anvil cells were applied. Following the quasi-isostructural volume reduction (3-5%) the new phase the magnetic-ordering temperature is drastically reduced, to ∼ 100 K, the direct and super-exchange interactions are drastically weakened, and the charge-transfer gap is substantially reduced. The high-pressure (HP) phases of the La and Pr oxides, at their inception, are composed of high- and low-spin Fe3+ magnetic sublattices, the abundance of the latter increasing with pressure but HP phases of the Eu, Y, and Lu oxides consist solely of low-spin Fe3+. Resistance and Mössbauer studies in La and Pr orthoferrites reveal the onset of a metallic state with moments starting at P > 120 GPa. Based on the magnetic and electrical data of the latter species, a Mott phase diagram was established.
Three Dimensional Structure of UMo8O26: Ordering of U-Vacancies
Authors: Zakharov N.D. , Werner P.
Published: June 2019

The structure and composition of UMo8O26 synthesized by solid state reaction method have been investigated by High Resolution Transmission Electron Microscopy (HRTEM), Selected Area Electron Diffraction, and EDX microanalysis. The ordering of U vacancies results in considerable enlargement of unit cell parameters: an=6.44 nm, bn=1.45 nm, cn=1.6 nm. It is build up of four layers piled up in c direction. Each following layer is shifted relative to previous one by vector bn/4. Eight hexagonal tunnels in each layer are filled by U atoms, while the eight others are vacant (V). Interaction between U cations and vacancies is driving force for ordering. The variation of stoichiometry can be a reason for appearance of incommensurate modulations in these crystals. It seems plausible that this structure might also exhibit superconductivity at low temperatures.
First-Principles Calculation of the Orbital Magnetic Moment of O and Cr in Half-metallic CrO2
Authors: Jeng Horng-Tay , Guo G. Y.
Published: June 2019

The electronic and magnetic properties of half-metallic CrO2 have been studied by using the full-potential linearized muffin-tin orbital method within the local spin-density approximation (LSDA)+U approach. It is found that the orbital magnetic moment of Cr atom is quenched while O atom exhibit relatively significant orbital moment in CrO2. For the Hubbard U of 3 eV, LSDA+U gives the orbital moment of -0.051μB/atom for Cr and -0.0025μB/atom for O, being in good agreement with the experimental orbital moments of -0.05 for Cr and -0.003μB/atom for O, respectively. In contrast, LSDA gives the orbital moment of -0.037 for Cr and -0.0011 μB/atom for O, being too small as compared with the magnetic circular dichroism measurements. For the larger U considered in this work, both spin and orbital moments almost increase linearly with respect to U.
Synthesis and Structural Characterization of Sol-Gel Derived Barium Zirconium Titanate Thin Films
Authors: Dixit A. , Savvinov A. , Majumder S.B. , Guo R.S. Katiyar R. , Bhalla A.S.
Published: June 2019

Barium zirconium titanate (BZT) thin films are attractive candidates for dynamic random access memories and tunable microwave devices. In the present work a wide range of Zr doped BaTiO3 thin films have been prepared by sol-gel technique. X-ray diffraction and micro-Raman scattering studies confirmed the structural phases in the powder and film of BZT and various structural transitions of BaTiO3 as a function of different Zr content compared well with the published result on ceramics and single crystalline BZT. The deposited films had smooth, crackfree and homogeneous microstructure and Zr content has strong influence on the evolution of the microstructures of the films. Some selected compositions of these films were characterized in terms of their dielectric properties and phase transition behavior. BZT film with 20 at % Zr had a ferroelectric to paraelectric transition in the vicinity of room temperature. Efforts are underway to optimize the annealing condition and grow epitaxial BZT films, with various Zr contents, on a suitable single-crystalline substrate.
New Layered Manganese Oxychlorides
Authors: Knee Christopher S. , Weller Mark T.
Published: June 2019

The synthesis, structure and preliminary magnetic characteristics of the new layered manganese oxide chlorides, Sr2MnO3Cl and Sr4Mn3O8-yCl2 are reported. Sr2MnO3Cl adopts a K2NiF4 type structure with sheets of MnO5 square based pyramids linked through oxygen and separated by SrCl layers; it is the end member of a new family of Ruddlesden-Popper type manganese oxide halides which includes the 3-layer member Sr4Mn3O8-yCl2. Magnetic susceptibility measurements reveal antiferromagnetic transitions at 95 K and 90 K for Sr2MnO3Cl and Sr4Mn3O8-yCl2 respectively. These materials demonstrate the extension of mixed anion chemistry to manganese and will increase flexibility in designing and controlling oxidation states of new GMR materials.
Synthesis, Structures, and Physical Properties of Yttrium-Doped Strontium Manganese Oxide Films
Authors: Francis Andrew J. , Salvador Paul A.
Published: June 2019

Cubic strontium manganese oxide is an end-member of the colossal magnetoresistive (CMR) family of manganese-based perovskites, Ln1-xAExMnO3. Because normal synthesis conditions lead to the 4-H hexagonal polymorph, high-pressure conditions are typically used to obtain the cubic perovskite polymorph. In this work, we describe the synthesis and structural/physical characterization of the cubic perovskite form of the high-alkaline-earth containing phases of Y1-xSrxMnO3 (x ≥ 0.7) as epitaxial thin films. Thin films of various stoichiometries were grown on single-crystal perovskite substrates SrTiO3, NdGaO3, and LaAlO3 using pulsed laser deposition. After optimizing deposition conditions, the perovskite polymorph is obtained using PLD at 800°C and 10-100 mTorr O2 for x=1, 0.9, 0.8, and 0.7, as demonstrated by x-ray diffraction. Epitaxial growth was determined to be cube-on-cube. Electrical property measurements demonstrated insulating behavior and no metal-insulator transition or magnetoresistive behavior, similar to related stable compounds.
Quantitative HRTEM investigation of an obtuse angle dislocation reaction in gold with a CScorrected field emission microscope
Authors: Jinschek Joerg R. , Kisielowski Ch. , Radetic T. , Dahmen U. , Lentzen M. , Thust A. , Urban K.
Published: June 2019

We investigate quantitatively the non periodic arrangement of atom columns surrounding an obtuse angle dislocation reaction in gold utilizing a CM200 FEG instrument equipped with a spherical aberration corrector. The in-plane component of the Burgers vector of the observed stair-rod dislocation is ⅙ [110]. Column positions are determined from single lattice images and compared with those from a reconstructed electron exit wave. We find that absolute position measurements of 1–3 pm require knowledge of the defocus to better than 1 nm which can be achieved by a reconstruction of the exit-plane wave. In contrast, a defocus value of 8.9 nm already leads to apparent displacements as large as 35 pm if single lattice images are considered. Such discrepancies are either caused by residual lens aberrations or by the superposition of delocalization effects at interfaces caused by defocusing of the objective lens. Commonly, however, only relative displacements are of interest. In this case the CS corrector improves the interpretability of single defocused lattice images with a remarkable signal to noise ratio which is advantageous for in-situ experiments. As an example for analyzing in-situ experiments we determine displacements recorded in a time resolved experiment of radiation induced atom motion on surfaces.
Nanometer Scale Composition Variations in Ge Quantum Dots on Si(100)
Authors: Zhang Yangting , Floyd Margaret , Drucker Jeff , Crozier P.A. , Smith David J. , Driver K.P.
Published: June 2019

Electron-energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) was used to measure nm-scale composition variations in Ge/Si(100) islands grown by molecular beam epitaxy (MBE) at substrate temperatures 400°C ≤T ≤700°C and a growth rate of 1.4 ML/min (1 monolayer, ML=6.78x1014 atoms / cm2). These measurements were correlated with island ensemble morphology determined by atomic force microscopy (AFM). The average Si concentration of the islands and Si/Ge interface width increased monotonically with growth temperature. Integrated island volumes measured by AFM were proportional to the equivalent Ge coverage, øGe, with slopes greater than one for the higher deposition temperatures. This result confirms that the islands grow faster than the Ge deposition rate. Linear behavior of the island volume vs. øGe curves implies that the average Ge composition is independent of island size. The volume at which islands change shape from pyramids to domes correlates well with the average Ge content of the islands in the context of simple strain-scaling arguments. For T=700°C, rapid Si interdiffusion precludes formation of pure Ge pyramids for growth at 1.4 ML/min. Growth at 4.8 ML/min kinetically stabilizes pure Ge pyramid clusters, allowing their formation prior to Si interdiffusion.
“Hairy Tube” Polymer Templates From Diblock Copolymer Thin Films
Authors: Tokarev Igor , Minko Sergiy , Stamm Manfred
Published: June 2019

We report about the fabrication of polymeric nanotemplates for the fabrication of regular arrays of nanocylindrical domains. Using combi-like macromolecules obtained by complexation of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) copolymer with a low molecular weight surfactant pentadecylphenol (PDP) we prepared thin polymer films deposited on a neutral substrate. The block-copolymer – PDP complex segregates into cylindrical morphology formed by P4VP-PDP fragments. The PDP molecules were easily removed by selective solvent (methanol) after annealing of the film. The resulting morphology consists of cylindrical channels of 7-8 nm in diameter oriented perpendicular to the substrate and regular packed in the hexagonal lattice with the period of 21 nm. Dry plasma etching, Atomic Force Microscopy (AFM), and Grazing Incidence Small Angle X-ray Scattering (GISAXS) were employed to characterize the films.
Synthesis and Characterization of Self-Assembled Piezoelectric ZnO Nanostructures and Integration with Si Processing
Authors: Cresce A. V. , Ali H. A. , Iliadis A. A. , Lee U. , Kofinas P.
Published: June 2019

The formation of 10 nm self-assembled ZnO nanoparticles on Si and SiO2/Si surfaces, using diblock copolymers, and wet chemical processing compatible with semiconductor manufacturing, is reported. The diblock copolymer, consisting of norbornene and a norbornenedicarboxcylic acid blocks with a 400 to 50 repeat unit ratio, was synthesized by ring opening metathesis polymerization. The microphase separation of the block copolymer was employed to grow spherical self-assembled ZnO nanoparticles The self-assembly of the inorganic nanoparticles was achieved at room temperature in the liquid phase by incorporating ZnCl2 to the carboxylic acid block, or by exposure of a solid film to diethyl zinc vapors. Subsequent room temperature wet chemical processing of the doped films resulted in the formation of zinc oxide, followed by the saturation of double bonds in the polymer backbone. The formation of ZnO was verified by x-ray photoelectron spectroscopy (XPS). Transmission electron microscopy (TEM ) micrographs show the size and distribution of the zinc oxide nanoclusters in the polymer matrix. This study provided information on the formation of zinc oxide structures in a self-assembled polymer matrix, with the intention of controlling the shape and distribution of zinc oxide domains. The doped diblock copolymer was applied on Si and SiO2/Si wafers, by standard spinon techniques, and its photolithographic patterning metalization was developed.
Manipulation of Germanium Nanocrystals in a Tri-Layer Insulator Structure of a Metal-Insulator-Semiconductor Memory Device
Authors: Teo L.W. , Heng C.L. , Ho V. , Tay M. , Choi W.K. , Chim W.K. , Antoniadis D.A. , Fitzgerald E.A.
Published: June 2019

A metal-insulator-semiconductor (MIS) device that consists of germanium (Ge) nanocrystals embedded in a novel tri-layer insulator structure is proposed for memory applications [1]. The tri-layer structure comprises a thin (≈5nm) rapid thermal oxidation (RTO) silicon dioxide (SiO2) layer, a Ge+SiO2 middle layer (6 - 20 nm) deposited by RF co-sputtering technique and a RF-sputtered silicon dioxide capping layer. High-resolution transmission electron microscopy (HRTEM) results show that Ge nanocrystals of sizes ranging from 6 –20 nm were found after rapid thermal annealing of the trilayer structure at 1000°C for 300s. The electrical properties of these devices have been characterized using capacitance versus voltage (C-V) measurements. A significant hysteresis was observed in the C-V curves of these devices, indicating charge trapping in the composite insulator. Comparison with devices having similar tri-layer insulator structure, but with a pure sputtered oxide middle layer (i.e. minus the Ge nanocrystals), clearly indicated that the observed charge trapping is due to the presence of the Ge nanocrystals in the middle layer. The C-V measurements of devices without the capping SiO2 layer exhibited no significant hysteresis as compared to the embedded Ge nanocrystal tri-layer devices. The HRTEM micrographs showed that the presence of the capping oxide is critical in the formation of nanocrystals for this structure. By varying the thickness of the middle layer, it was found that the maximum nanocrystal size correlates well with the middle layer thickness. This indicates that the nanocrystals are well confined by the RTO oxide layer and the capping oxide layer. In addition, Ge nanocrystals formed using a thinner middle layer were found to be relatively uniform in size and distribution. This structure, therefore, offers a possibility of fabricating memory devices with controllable Ge nanocrystals size.
Laser Guidance Deposition Technique for Patterning Microstructures Made of Nanoparticles with Varying Surface Functionality
Authors: Xu Juntao , Zhou Changgong , Grant Sheila , Nadgorny Edward , Drelich Jaroslaw
Published: June 2019

We present results on patterning microstructures using laser-guidance deposition of nanoparticles from particle-in-solvent suspensions. A laser beam axially confines and propels the particles inside a hollow optical fiber towards a substrate. Confining is provided by the gradient forces arising from light refraction or electrical forces on polarizable particles. The driving force results from the momentum conservation of photons scattered on particles. Polystyrene particles (100 and 400 nm in diameter) and gold particles (from 8 to 50 nm) with different surface organic functionality serve as a constructive material for fabrication of microstrips. In the experiments, the laser power varies from 0.1 to 1.6 W. The microstrips produced under different deposition conditions are studied using optical microscopy and atomic force microscopy. It was found that deposited polystyrene and gold particles form nanoclusters consisting of at least several particles. If deposited at an appropriate rate, such nanoclusters form multilayer microstrips of high particle density. The typical width of the microstrips ranges from less than 10 microns to 100 microns. This technique allows us to fabricate parallel arrays made of colloidal particles with different surface functionality, which seems to be an especially attractive approach for developing novel chemical and biological microsensors.
Carbon Nanotube Deposition using Helicon Plasma CVD at Low Temperature
Authors: Muroyama Masakazu , Yagi Takao , Inoue Kouji , Saito Ichiro
Published: June 2019

We developed a novel growth method of aligned carbon nanotubes. Aligned carbon nanotubes are grown on a metal catalyst on a glass substrate using biased Helicon plasma chemical vapor deposition (HPECVD) of CH4/H2 gases from 400 C to 500 C. The Helicon plasma source is one of the high-density plasma sources and is promising for low temperature carbon deposition. A Ni film was used as a catalyst to reduce the activation energy of the nanotubes' growth. The carbon nanotubes were deposited on the nickel catalysis layer selectively.
Chemical Precursor Routes to Nanostructured Non-oxide Ceramics
Authors: Forsthoefel Kersten M. , Pender Mark J. , Sneddon Larry G.
Published: June 2019

An efficient route to boron carbide, boron nitride, and silicon carbide ceramic nanofibers and nanotubules has been developed which employs newly developed molecular and polymeric precursors in conjunction with porous alumina templating methods. Melt infiltration or vacuum filtration of solutions of 6,6 -(CH2)6-(B10H13)2 or polyhexenyldecaborane through alumina templates followed by pyrolysis and dissolution of the membranes in 48% HF yielded boron carbide nanofibers or nanotubules. Boron nitride nanotubules were generated in a similar fashion by employing polyborazylene as a precursor, while silicon carbide nanotubules were generated from the commercially available allylhydridopolycarbosilane (AHPCS) polymeric precursor. In all cases, SEM and TEM analyses showed aligned, monodispersed ensembles of nanofibers or nanotubules. Structural control of the end products can be achieved through changes in concentration of the precursor solution, the number of alumina membrane treatments, and/or pore size of the alumina template.
Quantum Size Effect Silicon Structures via Molecularly Self-Assembled Hybrid Templates
Authors: Guliants Elena A. , Carreon Moises A. , Abeysinghe Don C. , Ji Chunhai , Anderson Wayne A. , Guliants Vadim V.
Published: June 2019

A novel approach for the synthesis of advanced functional inorganic materials with atomic-scale control over the size of periodic features on the sub-30 nm scale is presented. The key innovative aspect of this technique is the direct, bottom-up formation of a two-dimensional periodic array of spatially separated nanostructures in a self-organized thin-film porous template. This thin-film template is fabricated via biologically inspired hierarchical self-assembly of organic surfactant molecules in the presence of inorganic charged silicate species. The removal of organic molecules from such an organic/inorganic hybrid system creates a periodic array of pore channels of ∼3-30 nm diameter inside the thin-film silica template. This porous template is employed as a shadow mask to directly grow various functional nanostructures inside the confined environment of the periodic pore arrays. In the present study, silicon nanostructures were grown inside the templates by both chemical and physical (sputtering) vapor deposition. The quantum size effect was clearly pronounced in the room temperature photoluminescence spectra of the samples prepared by sputtering from a Si target, which makes the approach highly promising for the fabrication of nanoscale optoelectronic devices.
Comparison and Evolution of Copper CMP Consumable Technology
Authors: Evans David R.
Published: June 2019

Intensive investigation of copper CMP over the past decade has revealed that consumable technology is of critical importance. There are several reasons for this, but all are ultimately due to the chemical and material properties of copper and associated barrier layers. Moreover, in comparison to conventional dielectric polishing, copper CMP (and, perhaps, metal CMP in general) is of a much more chemical nature. This is a consequence of the fact that metal removal generally requires an oxidation-reduction mechanism while, in contrast, dielectric removal typically requires only simple hydrolysis. As any chemist knows, oxidation-reduction reactions are often notoriously hard to control and easily upset by contaminants. Of course, contaminants can be intentionally added to the chemistry for beneficial purposes in which case they become known as “proprietary additives”.

In addition, to the removal chemistry, abrasive and pad technology has also undergone considerable evolution. Indeed, free abrasive, fixed abrasive, and abrasiveless technologies have all been developed. In the case of fixed abrasive polishing, this has required modification of the pads as well, however conventional and abrasiveless polishing can be carried out with conventional polyurethane pads. This picture is further complicated by the various available hardware configurations and the use of multiplaten processes.
Silver Damascene Process with Cap Layer
Authors: Ota Masahiro , Tsujimura Manabu , Inoue Hiroaki , Ezawa Hirokazu , Miyata Masahiro
Published: June 2019

Development of semiconductors has proceeded according to broad frameworks such as the International Technology Roadmap for Semiconductors (ITRS). A key development in semiconductor technology involves the adoption of several new materials, such as Cu, low-k and high-k materials, and noble metals in capacitors, transistors, and/or interconnects. These developments will likely lead to wider application of the planarization process to new processes and new materials, and call for even stricter planarization performance requirements. One example involves planarizing Ag interconnects with an optimal cap layer configuration for reducing RC delays. The Cu interconnect process is currently used to reduce wire resistivity. One material that has been proposed as a successor to Cu is Ag. Many low-k materials have been developed with the goal of reducing dielectric constant (k). However, damascene design and matters such as cap layer configuration are also important considerations in reducing the effective dielectric constant (k eff). Our report herein begins by proposing Ni-B deposited by electroless plating as a candidate cap material, due to the following characteristics: (1) it offers good selectivity for Ag interconnects; (2) it provides good barrier effects through thermal processes; and (3) it provides good controllability of deposition rates. Next, we report that Ag damascene with Ni-B cap layer can be realized through electroplating and polishing of Ag interconnects. Although Ag polishing technologies are currently not fully developed, we suggest that they may nevertheless be successfully applied to polish Ag.
Mechanistic Understanding of Material Detachment During CMP Processing
Authors: Che Wei , Guo Yongjin , Bastawros Ashraf , Chandra Abhijit
Published: June 2019

A combined experimental and numerical approach has been devised to understand the abrasion aspects of material removal mechanisms of ductile copper film on silicon wafers during Chemical mechanical planarization. The experimentally observed trends of the deformation patterns and the force profiles from micro and nano-single scratch experiments are used to guide numerical simulation using finite element simulation at the continuum scale and molecular dynamics simulation at the atomistic scale. Such integrated approach has provided several plausible mechanisms for material detachments through a combination of surface plowing and shearing under the abrasive particles. The gained insights can be integrated into mechanismbased models for the material removal rate in these processes as well as addressing possible defect formation.
Simulation of Nanoscale Polishing of Copper with Molecular Dynamics
Authors: Ye Y. , Biswas R. , Morris J. R. , Bastawros A. , Chandra A.
Published: June 2019

We investigate the fundamental atomistic processes in chemical mechanical polishing of copper, by simulating the nanoscale polishing of a copper surface by a single abrasive particle. The atomistic mechanisms of an individual surface-polishing event are simulated with molecular dynamics using the embedded atom method. The nature of material removal, chip formation, material defects and frictional forces were investigated as a function of the cutting speed, depth of cut, and abrasive geometry. Nanometric cutting comprises of two steps: material removal as the tool machines the top surface, followed by relaxation of the work material to a low defect configuration, after the tool or abrasive particle has passed over the machined region. Chemical etching processes during planarization considerably improve the quality of the planarized surface and reduce defects in the bulk.
Effect of CMP Pad Exposure to Aqueous Media on the Pad Properties. Part 1. Dynamic Mechanical and Modulated DSC Analysis
Authors: Tregub A. , Moinpour M. , Sorooshian J.
Published: June 2019

Soaking of polyurethane-based CMP pad in oxide slurry, de-ionized water, and pH buffer solution, and its effect on thermal and mechanical properties of the pads was studied using Dynamic Mechanical Analysis and Modulated Differential Scanning Calorimetry. Pad softening due to soaking was established, and softening mechanisms are discussed. Diffusion of the aqueous medias to polyurethane pad was described using Fickian diffusion model.
Kinetics of Light-Induced Effects in Mixed-Phase Hydrogenated Silicon Solar Cells
Authors: Yuea Guozhen , Yan Baojie , Yang Jeffrey , Lord Kenneth , Guha Subhendu
Published: June 2019

We have observed a significant light-induced increase in the open-circuit voltage (Voc) of mixed-phase hydrogenated silicon solar cells. In this study, we investigate the kinetics of the light-induced effects. The results show that the cells with different initial Voc have different kinetic behavior. For the cells with a low initial Voc (less than 0.8 V), the increase in Voc is slow and does not saturate for light-soaking time of up to 16 hours. For the cells with medium initial Voc (0.8 ∼ 0.95 V), the Voc increases rapidly and then saturates. Cells with high initial Voc (0.95 ∼ 0.98 V) show an initial increase in Voc, followed bya Voc decrease. All light-soaked cells exhibit a degradation in fill factor. The temperature dependence of the kinetics shows that light soaking at high temperatures causes Voc increase to saturate faster than at low temperatures. The observed results can be explained by our recently proposed two-diode equivalent-circuit model for mixed-phase solar cells.
Hydrogenated Amorphous Silicon Thin Films with Nanocrystalline Silicon Inclusions
Authors: Belich T. J. , Thompson S. , Perrey C.R. , Kortshagen U. , Carter C.B. , Kakalios J.
Published: June 2019

Thin films of hydrogenated amorphous silicon containing nanocrystalline silicon inclusions (a/nc-Si:H) have been synthesized in an RF capacitively coupled PECVD system using a mixture of hydrogen diluted silane and helium, under deposition conditions at the edge of powder formation within the plasma. High resolution TEM confirms the presence of nanocrystallites as small as 2 nm in these films. Measurements of the optical absorption spectrum using CPM and PDS indicates a broadening of the Urbach slope in the a/nc-Si:H, compared to a-Si:H films, but no appreciable increase in midgap absorption. Despite the deposition conditions for the a/nc-Si:H being very different from those associated with producing optimal quality a-Si:H, the dark conductivity and photoconductivity values, and the sensitivity to light-induced defect creation in the a/nc-Si:H films are comparable to those in a-Si:H.
Metal Containing Link Formed in Amorphous Silicon Metal-To-Metal Antifuse
Authors: Hawley Frank , Issaq Farid , Ranaweera Jeewika , Lambertson Roy
Published: June 2019

A Metal-to-Metal (M2M) antifuse is formed using hydrogenated amorphous silicon as a dielectric material between two refractory metal electrodes. The M2M antifuse is used as a programmable device in an FPGA, where it is placed between two interconnect metal layers of a Logic CMOS process. The M2M device may then be programmed to interconnect logic circuits. The resulting programmed link is an alloy of amorphous silicon and barrier metal that forms a low resistance path between the logic circuits.
Lifetime Measurements of Stain Etched and Passivated Porous Silicon
Authors: Guerrero-Lemus Ricardo , Ben-Hander Fathi A. , Ballif Cristoffer , Kenanoglu Ali , Borchert Dietmar , Hernández-Rodríguez Cecilio , Rodríguez Tomás , Martínez-Duart José M.
Published: June 2019

In this work we present the first experimental study of photocarrier lifetimes in p-type and n-type Si substrates in which stain etched porous silicon (PS) has been formed on the surface. The lifetime values have been obtained before and after the surface passivation of the samples. The surface pasivation has been produced by two different techniques: (i) hydrogen passivation by immersion of the samples in a HF solution; and (ii) deposition of SiNx in a plasma enhanced chemical vapour deposition system. The results show a degradation of the photocarrier lifetime when the porous layers are not adequately passivated. This lifetime degradation is mainly associated to a large concentration of rapid recombination centres located at the Si/PS interface. We have also detected a weak influence of the PS outermost dangling bonds to the photocarrier lifetimes.
Effect of SiO2 Capping Layer on a Laser Crystallization of a-Si Thin Film
Authors: Kang Myung-Koo , Kim Hyun Jae , Kang Sook Young , Lee Su-Kyung , Kim Chi-Woo , Chung Kyuha
Published: June 2019

Effect of SiO2 capping layer(C/L) on recrystallization of amorphous Si (a-Si) film was investigated. When a thick C/L over 500 Å was deposited on an a-Si film before crystallization, fine p-Si grains less than 100nm were obtained at full range of energy density window. However, when a thin C/L below 200 Å was used, Si-melt spouted out through C/L at over critical energy density. When Si-melt started spouting, abrupt change of grain size also occurred. These large grains could be explained by a non-uniformity of heat flow caused by Si-melt spouting. With this polycrystalline Si (p-Si) material having appreciable grain size protected by C/L, fabrication of low-cost Low Temperature Poly Si (LTPS) without additional cleaning of p-Si surface could be successfully developed.
Observation and Annealing of Incomplete Recrystallized Junction Defects due to the Excimer Laser Beam Diffraction at the Gate Edge in Poly-Si TFT
Authors: Nam Woo-Jin , Park Kee-Chan , Jung Sang-Hoon , Park Soo-Jeong , Han Min-Koo
Published: June 2019

Incomplete recrystallized junction defects of self-aligned, excimer laser annealed polycrystalline silicon (poly-Si) thin film transistor (TFT) was investigated by high-resolution transmission electron microscopy (HR-TEM). TEM observation and simulation result verify that the laser irradiation intensity decreased remarkably at the junction due to diffraction of laser beam at gate electrode edge. We proposed oblique-incidence excimer laser annealing method and successfully eliminated the residual junction defects.
2-Dimensional Controlled Large Lateral Grain Growth on the Floating Amorphous Silicon Film by Excimer Laser Recrystallization
Authors: Song In-Hyuk , Kang Su-Hyuk , Nam Woo-Jin , Han Min-Koo
Published: June 2019

We have successfully obtained large lateral grains with well-controlled grain boundary. The proposed excimer laser annealing (ELA) method produces 2-dimensionally controlled grain growth because the temperature gradient is induced in two directions. Along the channel direction, the floating active structure produces large thermal gradient due to very low thermal conductivity of the air-gap. Along the perpendicular direction to the channel, the surface tension effect also produces thermal gradient. The proposed ELA method can control the grain boundary perpendicular and parallel to current path with only one laser irradiation.
Mechanical Stress and Process Integration of Direct X-ray Detector and TFT in a-Si:H Technology
Authors: Lee Czang-Ho , Chan Isaac , Nathan Arokia
Published: June 2019

This paper presents an alternate strategy to reduce the mechanical stress issues pertinent to the process integration of molybdenum/hydrogenated amorphous silicon (Mo/a-Si:H) Schottky diodes and thin film transistors (TFTs), used as X-ray sensor pixels for medical imaging. The previous approach was to minimize the intrinsic stress in the Mo layer through appropriate process conditions and film thickness, but over narrow process latitude and with a compromise in X-ray sensitivity. Alternatively, the mechanical stress in Mo can be reduced by reducing and/or avoiding the extrinsic stress exerted on Mo by the underlying films through a different masking sequence in the fabrication. This modified process allows for a more flexible design of the Mo layer for enhanced X-ray sensitivity, while maintaining the mechanical integrity of the various layers. Also, the performance of the Schottky diode is improved, in terms of its forward current. The pixel shows good linearity in the X-ray response over the range of 40 ∼ 100 kVp.
Origin of the Low-Energy Photoluminescence in Microcrystalline Silicon Films
Authors: Lee Joon-Yong , Park Dong-Hyun , Yoon Jong-Hwan
Published: June 2019

In this work we have investigated the low-energy photoluminescence (PL) band with a peak between 0.8 eV and 1.0 eV for microcrystalline silicon films (μc-Si:H) grown under various growth conditions. At least four subbands are observed, the peaks of which are located near 0.80 eV, 0.87 eV, 0.92 eV, and 0.97 eV, respectively. It is suggested that the low-energy PL band basically arises from a superposition of these subbands, whose intensities strongly depend on deposition conditions, and thus its peak is determined by the sum of these subband intensities. From the results, it is suggested that the subband centered at 0.92 eV originates from defect-related radiative recombination in the amorphous phase rather than radiative band tail-to-tail transitions in the grain boundaries.
Fabrication of Novel TFT LCD Panels with High Aperture Ratio Using a-SiCO:H Films as a Passivation Layer
Authors: Hong W.S. , Jung K.W. , Hwang B.K. , Cerny G. , Yang S.H. , Choi J.H. , Chung K.
Published: June 2019

Fabrication of a novel TFT-LCD panel, using amorphous silicon oxycarbide (a-SiCO:H) films as a passivation layer, was successfully demonstrated for the first time. The a-SiCO:H low-k films were deposited using a standard PECVD (plasma-enhanced chemical vapor deposition) reactor from a gas mixture of trimethylsilane[Si(CH3)3H] and N2O. The resulting films have a dielectric constant between 2.7 and 3.5 and high optical transmittance in the range of visible light

The transfer characteristics of the TFT's having a-SiCO:H as a passivation layer were comparable with that of a conventional TFT with a PECVD-grown SiNx passivation layer. Stability of the resulting TFT was performed under prolonged bias conditions, and the source-drain current was fairly constant over the test period. The LCD panel with the a-SiCO:H passivation layer showed 30% higher brightness than that of the standard panel.
Carrier Transport and Recombination In A-SI:H P-I-N Solar Cells in Dark and Under Illumination
Authors: Deng J. , Pearce J.M. , Vlahos V. , Koval R.J. , Collins R.W. , Wronski C.R.
Published: June 2019

A study has been carried out on the forward bias dark current and the short circuit current -open circuit voltage characteristics of a-Si:H p-i-n solar cells over wide range of illumination intensities. Results are presented with superposition of these characteristics over extended current voltage regimes. This and the observed separation between these characteristics are consistent with the arguments presented based on first principle arguments. The conclusions drawn about the role of photo-generated carrier lifetimes, the densities of defects and the potential barriers in the i-layers adjacent to the n and p contacts are confirmed by numerical simulations. The key role of these potential barriers to the split in the characteristics offer new insight into both why the lack of superposition has been observed and the erroneous conclusions drawn about carrier transport for a-Si:H solar cells in the dark and under illumination.
Polymorphous Silicon Films Produced in Large Area Reactors by PECVD at 27.12 MHz and 13.56 MHz
Authors: Águas H. , Raniero L. , Pereira L. , Fortunato E. , Cabarrocas P. Roca i , Martins R.
Published: June 2019

This work refers to a study performed on polymorphous silicon (pm-Si:H) at excitation frequencies of 13.56 and 27.12 MHz in a large area PECVD reactor. The plasma was characterised by impedance probe measurements, aiming to identify the plasma conditions that lead to produce pm-Si:H films. The films produced were characterised by spectroscopic ellipsometry, infrared and Raman spectroscopy and hydrogen exodiffusion experiments, which are techniques that permit the structural characterisation of the pm-Si films and to study the possible differences between the films deposited at 13.56 and 27.12 MHz. Conductivity measurements were also performed to determine the transport properties of the films produced. The set of data obtained show that the 27.12 MHz pm-Si:H can be grown at higher rates with less hydrogen dilution and power density, being the resulting films denser, chemically more stable and with improved performances than the pm-Si:H films grown at 13.56 MHz.
Structural Characterization of Microcrystalline Silicon Solar Cells Fabricated by Conventional RF-PECVD
Authors: Li Liwei , Li Yuan-Min , Selvan J. A. Anna , Delahoy Alan E. , Levy Roland A.
Published: June 2019

Absttact:

Direct structural characterization of single junction p-i-n type μc-Si:H solar cells prepared in a single chamber, batch process type RF-PECVD system has been carried out using Raman scattering, XRD, and AFM. The overall degree of microcrystallinity of μc-Si:H i-layers is presented in terms of the ratio of peak intensities (Ic/Ia) of Raman shift at around 520 cm-1 and 480 cm-1, respectively. Strong correlations among device performance, i-layer structural properties, and uniformity have been established using information provided by such direct characterization. Our data support the notion that stable, high quality μc-Si i-layers are grown near the ‘edge’ of microcrystalline-to-amorphous phase transition. Solar cells made from such optimal areas exhibit moderate microcrystallinity (moderate Ic/Ia values). Preferential orientation corresponding to Si (220) planes was observed on those optimal solar cells, which also exhibit less-regular surface morphologies and lower surface roughness compared to that observed on solar cells with mixed-phase or highly crystalline Si:H i-layers.
Hollow Electrode Enhanced RF Glow Plasma Generation and its Application to the Fast Deposition of Microcrystalline Silicon Films
Authors: Tabuchi Toshihiro , Takashiri Masayuki , Toyoshima Yasumasa , Mizukami Hiroyuki
Published: June 2019

A hollow electrode enhanced RF glow plasma excitation technique has been newly developed. In this technique, the reactor is divided into a capacitively-coupled RF glow discharge space and a processing space by the counter electrode, which includes a hollow structure and is placed between a RF electrode and the substrate. After introducing hydrogen gas into the chamber and applying RF power to the electrode, high intensity plasma emission is observed near and inside the hollow structure attached to the counter electrode. By using hollow RF electrode excitation in addition to the hollow counter electrode technique, it is found that plasma emission is further enhanced. The application of these discharge types for semiconductor processing is studied in the case of plasma enhanced chemical vapor deposition (PECVD) of hydrogenated microcrystalline silicon thin films. High crystallinity, photo-sensitivity and a maximum deposition rate of 4.9nm/s can all be achieved at a plasma excitation frequency of 13.56MHz and a temperature of 300°C. Properties of these plasmas are investigated by observing the plasma emission pattern and optical emission spectrum analysis. It is found that, using additional hollow RF electrode discharge, faster processing of device grade hydrogenated microcrystalline silicon thin films can be achieved under lower RF power compared to hollow counter electrode technique alone.
Reactive Pulsed Laser Deposition of Microcrystalline Ge-based Thin Films
Authors: Wills Matthew R. , Shinar Ruth , Constant Alan P.
Published: June 2019

Pulsed laser deposition (PLD) was used to grow microcrystalline thin films of germanium (Ge) and Ge-carbon (Ge,C) alloys on fused quartz and silicon substrates at substrate temperatures 25°C ≤ Ts ≤ 325°C. The films were analyzed structurally with x-ray diffraction (XRD), optically, electrically with four-point probe measurements, and chemically with x-ray photoelectron spectroscopy (XPS). XRD results displayed a varying degree of crystallinity, with the most crystalline films obtained at Ts > 150°C. The resistivity of the Ge films decreased with increasing temperature, displaying a significant decrease for the films deposited at Ts ≥ 230°C. The growth conditions for Ge films served as a starting point for low-temperature deposition of Ge,C alloys with up to 5% C. The effects of Ts and carbon concentration on film properties are discussed.