bluuebunny/crossref_metadata_2025 huggingface dataset:
Interaction Between Ceria and Hydroxylamine
Authors: Tamilmani Subramanian , Shan Jilei , Huang Wayne , Raghavan Srini , Small Robert , Shang Cass , Scott Brandon
Published: June 2019

Ceria containing slurries are increasingly used in the chemical mechanical polishing of CVD silicon oxide films to obtain STI structures. Unlike silica or alumina, ceria has redox characteristics. Because of this characteristic, removal of ceria particles from planarized surfaces may be possible using chemical reagents that can participate in redox reactions. One such reagent is hydroxylamine, which is already being used in copper CMP. The objective of the work reported in this paper was to characterize the reaction between ceria and hydroxylamine, especially with respect to dissolution of ceria particles. A kinetic study of the dissolution of ceria in hydroxylamine solutions maintained at various pH values has been performed. The extent and kinetics of dissolution of ceria has been determined by ICPMS. Removal of ceria particles from oxide surfaces using hydroxylamine-based chemistries has been investigated.
Slurry Admittance and Its Effect on Polishing
Authors: Evans David R.
Published: June 2019

Conventional polishing process variables such as down force, platen speed, slurry flow rate, etc. tend to be both coupled together and indirect. Within this context, one might argue that the net rate of slurry admission or concomitantly, effective volume of slurry between the substrate and pad is a direct process parameter, which is affected by polishing pressure, substrate-pad relative velocity, pad wear and texture, etc. In this work, the role of slurry admittance is investigated by direct control of interference between the pad surface and the carrier retainer ring. Both fixed and dynamic implementations are investigated. Observed patterns of material removal on substrates polished with a fixed orientation are correlated and discussed.
CMP Revisited for the MEMS/Foundry Era
Authors: Camilletti Lawrence , Semiconductor Jazz
Published: June 2019

Business/foundry driven requirements have necessitated the creation of modified ILD CMP processes for terminal metal-die planarization for BiCMOS SOC/MEMS applications. Therefore, despite much CMP process evolution, this paper ‘steps-back’ to test CMP assumptions first introduced within ILD process norms on these new applications at 10X typical process topographies. Evaluation of planarization targets, density effects, oxide budgets, as well as associated integration, throughput and metrology considerations within this expanded regime are discussed. ANOVA on inter- and intra-die (WIWNU and WIDNU) variation are used to quantify results throughout the work.
Polishing Behavior of the Various Interconnect Thin Films in Cu Damascene Process with Different Slurries
Authors: Zantye Parshuram B. , Sikder Arun K. , Kumar Ashok
Published: June 2019

Chemical Mechanical Polishing is a key technology for Cu damascene wiring process in integrated circuit (IC) manufacturing. It is important to understand the effects of mechanical and tribological properties of the coatings that form a part of Cu damascene structure on the CMP process in order to successfully evaluate and implement these materials. In this paper, we present tribological properties of different interlayer coatings (SiLKTM, Ta and Cu) during their CMP process using different Cu and barrier selective slurries. A micro CMP tester was used to study the fundamental aspects of the CMP process. The coefficient of friction (COF) and acoustic emission (AE) signals were acquired in situ to monitor the process and to see the difference in polishing behavior of these coatings. The issues of end point detection and slurry selectivity are discussed in detail.
Integrated Chip-Scale Prediction of Copper Interconnect Topography
Authors: Park Tae , Tugbawa Tamba , Cai Hong , Xie Xiaolin , Boning Duane
Published: June 2019

In this work, we present an integrated prediction of thickness variations in electroplating and chemical mechanical polishing (CMP) processes across an entire chip for random layouts. We achieve chip-scale prediction by first calibrating both electroplating and CMP models with experimental data using the same test mask. Using the calibrated plating model in conjunction with a discretized and binned layout extraction for a random chip layout, a prediction of plated copper topography is then performed. Finally, using the plated thickness prediction as the initial condition, the CMP model predicts the dishing and erosion across the chip. Layout geometry extraction for each discretized region of a chip as well as layout parameter manipulation and model output integration are all critical elements, in addition to the model development itself, enabling the integrated chip-scale prediction of final copper interconnect thickness variation.
Low Temperature a-Si:H Pixel Circuits for Mechanically Flexible AMOLED Displays
Authors: Nathan Arokia , Striakhilev Denis , Servati Peyman , Sakariya Kapil , Kumar Anil , Karim Karim S. , Sazonov Andrei
Published: June 2019

This paper presents the first demonstration of amorphous silicon (a-Si:H) thin film transistor (TFT) circuit integration on plastic substrates. The circuits compensate for material shortcomings such as metastable threshold voltage (VT) shift and high contact resistance, to supply stable and predictable currents to drive organic light emitting diode (OLED) displays on plastic. Various drive circuits were fabricated and tested. The simplest pixel driver circuit possible is the two TFT voltage-programmed circuit, which is very susceptible to any shift in VT of the drive TFT. To overcome this problem, we have developed current-programmed pixel circuits based on the current mirror circuit family, which include the simple and cascode current mirrors. The OLED current in these circuits is virtually independent of any VT shift or mobility variation in the drive TFT. Results show that the circuits provide higher linearity and dynamic range than currently available pixel circuits while minimizing the pixel area.
Curved Silicon Electronics
Authors: Wang Linlin , Ast Dieter G. , Bhargava Peeyush , Zehnder Alan T.
Published: June 2019

An electronic imaging system using a curved image sensor can use a faster lens, and cover a greater field of view, than an imaging system using a planar sensor. The simpler lens systems also weight less, a decisive advantage in portable applications.

This paper describes a method to fabricate a curved silicon substrate from a flat wafer containing appropriate circuits. To curve the substrate, the processed wafer is diced, by dry-etching from the backside, into 1x1cm tiles. The tiles are separated by 0.5mm gaps, which are bridged, in turn, by a dense array of 45x100μm gold leads formed by electroplating using lithographically defined leads as seeds. Two methods were used to curve the wafer. In the first one, the wafer was bonded with epoxy to a PMMA disk, and then curved by heating the sandwich, under a load of ∼ 230gr, for 1.5 hrs at 130°C in a concave metal mold with a radius of curvature of 7.8cm. In the second method, the wafer was put into a curved metal mold, radius 14cm, loaded with 230gr, and heated to 290°C for 2 hrs. The normal and shear strains accommodated by the flexible interconnects were measured by analyzing their deformation. The experimentally measured strains are compared with a model that calculates the deformation required to deform a flat sheet into a spherical surface.
PMODTM-based Direct Thin Film Imaging, DTFITM, on Flexible Substrates
Authors: Roman Paul J. , Madsen Harold O. , Suh Seigi , Svendsen Leo G. , Mukherjee Shyama P. , Jamora Aleta , Fury Michael A. , Ip Katy
Published: June 2019

PMOD (Photochemical Metal Organic Deposition)-based DTFI (Direct Thin Film Imaging) methodology is a demonstrated means for patterning organic materials on flexible (plastic) substrates. This process is used to pattern 1-micron features at an aspect ratio of 8:1 using contact lithography. Use of oxygen plasma RIE etch to transfer the hard mask pattern to the organic material allows for good sidewall angle control. High etch selectivity between the novolac polymer and PMOD TiOX hard mask (< 800:1) makes the use of very thin hard masks (∼ 200 angstroms) to pattern thick organic films (<10 microns) possible. Selective removal of the PMOD TiOX (TiO2) hard mask makes this process amenable to patterning of functional organic structures fabricated from materials chosen for their desired properties (e.g., glass transition temperature (Tg), etch resisitance, optical properties, mechanical properties, etc.) not their ability to be photopatterned (e.g., photoresist).
Flexible Magnetics: Magnetic Lithography and Fabrication of Magnetic Masks on Thin Plastic Substrates
Authors: Bandić Z. Z. , Xu H. , Baglin J.E.E. , Albrecht T. R.
Published: June 2019

Flexible magnetic lithography is a process qualitatively analogous to contact optical lithography which transfers information from a patterned magnetic mask (analog of optical photomask) to magnetic media (analog of photoresist), and is interesting for applications in instantaneous parallel magnetic recording. The magnetic mask consists of patterned soft magnetic material (FeNiCo, FeCo) on a flexible plastic substrate, typically Polyethylene Teraphtalate (PET). When uniformly magnetized media is brought into intimate contact with the magnetic mask, an externally applied magnetic field selectively changes the magnetic orientation in the areas not covered with the soft magnetic material. Flexible substrate of the magnetic mask o.ers superior compliance to magnetic media which is likely to have imperfect flatness and surface particulate contamination.

Although magnetic in physical nature, flexible magnetics draws interesting parallels to flexible electronics, especially in challenges of fabrication of sub-micron patterns on thin flexible plastic substrates. We fabricated samples of sub-micron patterned FeCo and FeNiCo magnetic masks on PET substrates by using combined lamination/release process of PET films. Rigid substrates, typically silicon or quartz were initially laminated with PET films and processed using standard fabrication procedures. After completing magnetic mask device fabrication, PET films were released from the rigid substrates.

We successfully transferred patterns from magnetic masks to hard disk CrPtCo-based magnetic media. The details of the method, including physics of the magnetic lithography pattern transfer, fabrication of the magnetic mask on flexible PET substrates, lamination and release of PET films, and magnetic force microscopy (MFM) images of the magnetic transition patterns are reported.
Characterizing the Modulus and Hardness of Photopatternable Silicone Compositions Using Depth Sensing Nanoindentation
Authors: Harkness Brian R. , Schalek Richard L. , Sarmah Satyen K. , Drzal Lawrence T.
Published: June 2019

The mechanical properties of two cured silicone monolithic specimens with targeted bulk moduli of 300 and 10 MPa have been evaluated by DMA and regionally by CSM nanoindentation. The results showed that the mechanical properties of the monolithic samples were heterogeneous, with the DMA and nanoindention results only in agreement at the midplane of cleaved bulk samples. The specimens showed a significantly higher modulus at the sample surfaces compared to the bulk. Thin films of the same silicones displayed a modulus closer to that of the bulk sample surface. The nanoindentation results of this study were reliable and consistent, and are being used to assess the effects of material and microelectronic device integration processes on the mechanical properties of a series of low modulus photopatternable silicone thin film dielectrics.
Electronic Energy Transfer from Excitons Confined in Silicon Nanocrystals to Molecular Oxygen
Authors: Gross E. , Kovalev D. , Künzner N. , Diener J. , Koch F. , Timoshenko V.Yu. , Fujii Minoru
Published: June 2019

We report on efficient electronic energy transfer from excitons confined in silicon (Si) nanocrystals to molecular oxygen (MO). The remarkable photosensitizing properties of Si nanocrystal assemblies result from a broad energy spectrum of photoexcited excitons, a long triplet exciton lifetime and a highly developed surface area. Quenching of photoluminescence (PL) of Si nanocrystals by MO physisorbed on their surface is found to be most efficient when the energy of excitons coincides with the triplet-singlet splitting energy of oxygen molecules. Spectroscopic analysis of the quenched PL spectrum evidences that energy transfer is accompanied by multi-phonon emission. From time-resolved measurements the characteristic time of energy transfer is found to be in the range of microseconds. The dependence of PL quenching efficiency on the surface termination of nanocrystals is consistent with short-range resonant electron exchange mechanism of energy transfer. The energy transfer to oxygen molecules in the gaseous phase at elevated temperatures is demonstrated.
Time-Resolved Gain Dynamics in Silicon Nanocrystals
Authors: Negro L. Dal , Cazzanelli M. , Daldosso N. , Pavesi L. , Priolo F. , Franzò G. , Pacifici D. , Iacona F.
Published: June 2019

Time-resolved variable stripe length (VSL) experiments on a set of silicon nanocrystal waveguides obtained by plasma enhanced chemical vapor deposition (PECVD) have revealed a fast recombination dynamics (20 ns) related to population inversion under 6 ns optical pumping at 355 nm. Modal gain values about 10 cm-1 have been measured at 760 nm by VSL technique for the fast recombination component while optical losses about 15 cm-1 are measured for the integrated signal in the slow (lifetime of about 10 μs) recombination tail. Threshold behavior in the emission intensity together with a pumping length and pumping power dependence of both the intensity and the time duration of the fast recombination component has been observed. These results are explained within an effective four level model to describe the strong competition among different Auger processes and stimulated emission.
Thermo-Electric Performance of poly-Si0.7Ge0.3
Authors: Wijngaards D.D.L. , Wolffenbuttel R.F.
Published: June 2019

The performance of poly-Si0.7Ge0.3 as a thermo-electric material that is fully process compatible with IC fabrication in silicon been fully analyzed and characterized. The application is in on-chip thermal stabilization of a micromachined platform in silicon. A Seebeck coefficient α= -174 μV/K and a figure of merit z= 0.173 has been obtained for n-type material. Measurements indicate a cooling capability of 2.1 K below ambient temperature.
Electro-Optical Properties and Interfacial Charges in Polymer-Dispersed Liquid Crystal Devices
Authors: Ramsey Robert A. , Sharma Suresh C. , Henry Robert M. , Atman Jay B.
Published: June 2019

Polymer-dispersed liquid crystal (PDLC) is a composite material that consists of sub micron-size droplets of liquid crystalline (lc) material dispersed in a polymer matrix. A device is usually assembled by sandwiching PDLC between ITO-coated glass plates. The electro optical properties of such a device can be controlled by the application of electric fields; the device acts as a “switch” for the transmission of light. The transmission of light through the device can be controlled between almost zero and 100% by applying ac electric fields. The dielectric properties of the lc and polymer, shape and size distribution of the lc droplets in the PDLC, amplitude and frequency of the applied electric field are among the important parameters for optimizing the performance of such a device. We have investigated the optical properties of PDLC devices fabricated by using several different phase-separation techniques and different lc/polymer materials. We present results for the switching characteristics of these devices as functions of applied electric fields and the size-distribution of the lc droplets. We also present results that reinforce the influence of the interfacial charges on the optical properties of the PDLC devices.
Alignment of Rigid-Rod Polypeptide Chains by Solvent Quenching
Authors: Wang Yuli , Chang Ying Chih
Published: June 2019

We introduce a simple “solvent quenching” approach to align the rigid-rod à-helical poly(α-benzyl-L-glutamate) (PBLG) chains in the surface-grafted monolayer. By sequentially treating with a good solvent and a poor solvent, a unidirectionally aligned PBLG monolayer with an average tilt angle as small as 3° is obtained.
In-situ electrical and spectroscopical techniques for the study of degradation mechanisms and life time prediction of organic based electronic material systems
Authors: Manca Jean , Goris Ludwig , Kesters Els , Lutsen Laurence , Martens Tom , Haenen Ken , Nesladek Milos , Sanna Ornella , Vanderzande Dirk , D'Haen Jan , Schepper Luc De
Published: June 2019

In order to tailor the synthesis of new robust organic materials for electronic applications and to guarantee the required life time for the emerging commercial plastic electronic applications it is of key importance to understand the underlying degradation mechanisms. Since plastic electronics is a rather young technology introducing new material systems, its reliability is characterized by new failure and degradation mechanisms, a relatively high amount of early failures and multi-modal failure distributions. To understand the mechanism responsible for a given failure or degradation mode, it is essential to study it separately, through appropriate test structures and test techniques. Powerful techniques for this purpose are a.o. analytical techniques (SEM, TEM, SPM,..), in-situ electrical measurement techniques and spectroscopical techniques (in-situ FTIR, in-situ UV-Vis, PDS). The benefits of these in-situ techniques in the reliability study of organic based electronics will be illustrated in this contribution.
The Effect of Doping on the Energy Distribution of Localized States and Carrier Transport in Disordered Organic Semiconductors
Authors: Arkhipov Vladimir I , Heremans Paul , Emelianova Evgenia V. , Adriaenssens Guy J. , Bässler Heinz
Published: June 2019

Doping of a disordered organic semiconductor gives rise to additional energy disorder due to the Coulomb interaction between randomly distributed dopant ions and carriers localized in intrinsic hopping sites. Although the carrier density increases with increasing doping level the additional energy disorder can significantly reduce the carrier hopping mobility. At higher doping levels the filling of deep states takes over, which leads to steeply increasing mobility at high dopant concentrations.
Exciton Dissociation In Doped Conjugated Polymers
Authors: Arkhipov Vladimir I. , Heremans Paul , Emelianova Evgenia V. , Bässler Heinz
Published: June 2019

A model of carrier photogeneration in doped conjugated polymers is formulated. The model suggests that dissociation of a relaxed exciton into a Coulombically bound geminate pair (GP) occurs at a charge transfer center that consists of a polymer chain and a nearby electron acceptor. Further dissociation of the GP into free carriers is facilitated either by the kinetic energy of the zero-point oscillation of the on-chain carrier at low dopant concentrations or by the interfacial potential barrier for geminate pair recombination in polymer/electron acceptor blends.
Thermocapillary Actuation of Liquids Using Patterned Microheater Arrays
Authors: Valentino Joseph P. , Darhuber Anton A. , Troian Sandra M. , Wagner Sigurd
Published: June 2019

We demonstrate a microfluidic actuation technique capable of directing nanoliter liquid samples on the surface of a glass substrate through the use of both electronically addressable heater arrays and chemical patterning. Pathways for liquid movement are delineated by the arrangement of microheaters, which also provide the thermocapillary actuating force. The drops are confined to these pathways by a selectively deposited fluorinated monolayer, which defines the channel edges. Operating voltages in the range of 2-3 V is used to move, split, and trap liquids. This fluid transportation technique enables direct access to liquid samples for handling and diagnostic purposes and offers a low power alternative to existing microfluidic systems.
ATRP Synthesis and Characterization of μ,αω-allyl-terminated Macromonomers as Precursors for End-linked Gels and Hydrogels
Authors: Vojtova Lucy , Turro Nicholas J. , Koberstein Jeffrey T.
Published: June 2019

Synthesis of α,ω-allyl-terminated telechelic macromonomers based on poly(tert-butyl methacrylate) (poly(t-BMA)) and poly(methacrylic acid) (poly(MAA)) was studied with the aim of preparing end-linked gels and hydrogels. Low molecular weight α-allyl-terminated poly(t-BMA) macromonomers with narrow polydispersities (Mw/Mn = 1.16) were synthesized via controlled atom transfer radical polymerization (ATRP) using a Cu(I)Br/N,N,N',N',N',N'-hexamethyltriethylenetetraamine catalyst system in conjunction with an allyl-2-bromoisobutyrate as the functional initiator. The polymerizations exhibited a linear increase of molecular weight in direct proportion to the monomer conversion and first-order kinetics with respect to monomer concentration. No significant difference was found between using polar or non-polar solvents (tetrahydrofuran or benzene, respectively). Optimization of reaction conditions to obtain the highest degree of active terminal bromine is discussed. Quenching the ATRP reaction with allyltributyltin yielded α,ω-allyl-terminated poly(t-BMA) macromonomers by replacing the terminal bromine with ω-allyl functional group. Poly(MAA) macromonomers were prepared by deprotection of the tert-butyl group from α,ω-allyl-terminated poly(t-BMA) macromonomers using concentrated trifluoroacetic acid at room temperature. Successful synthetic steps were confirmed by 1H NMR, FT-IR and MALDI-TOF MS analyses. The α,ω-allyl-terminated macromonomers were proven to be candidates for further polymerization by forming end-linked, non-soluble gels.
From the Spider to the Web: Biomimetic Processing of Protein Polymers and Collagen
Authors: Stephens Jean S. , Rabolt John F. , Fahnestock Stephen R. , Chase D. Bruce
Published: June 2019

The use of electrostatic forces to shape materials processed from solution provides exciting opportunities to enhance material properties by creating new structures and morphologies during processing. In this context we report the formation of nanoscale webs composed of interconnected electrospun polymer fibrils. These nanowebs have been formed from synthetic spider silk, collagen, and denatured collagen when they are electrospun from various concentrations of formic acid. These nanowebs have been characterized by field emission scanning electron microscopy (FESEM) in order to characterize their morphology and measure their surface areas.
Spray Drying FunctionalizedMesostructured Colloids
Authors: Alberius Peter , Andersson Nina , Bergström Lennart
Published: June 2019

An industrially viable production method is a prerequisite for the commercialization of templated mesostructured materials, e.g. as carriers of various functionalities in coatings, in the coatings of ink jet paper and liquid chromatography. A small pilot plant was constructed for the continuous production of well ordered mesostructured materials (>10g/h) that can easily be scaled to an industrial process. The silica colloids have a well controlled internal mesostructure and are spherical with a mean diameter of 1-5μm. The mesoscopic pores in the calcined materials are accessible to relatively large molecules; up to 25 % (by weight) of the cationic dye Janus Green B could be adsorbed from an aqueous solution. We have also demonstrated how optically functional silica colloids could be prepared in a one-pot synthesis by introducing different dyes into the precursor solution.
Temperature Dependence of the Self-Assembled Styrene Based Random Ionomers in Aqueous Solution
Authors: Oh Sung-Hwa , Song Ju-Myung , Kim Joon-Seop , Oh Hyang-Rim , Yu Jeong-A
Published: June 2019

Solution behaviors of poly(styrene-co-sodium methacrylate) were studied by fluorescence spectroscopic methods using pyrene as a probe. The mol% of methacrylate was in the range 3.6–9.4. Water and N,N-dimethylforamide(DMF) mixture was used as a solvent (DMF/water = 0.2 mol %). The critical micelle (or aggregation) concentrations of ionomers and the partition coefficients of pyrene were obtained the temperature range 10–80°C. At room temperature, the values of CMCs (or CACs) were in the range 4.7 ×10-6 5.3 ×10-6 g/mL and we could not find any notable effect of the content of ionic repeat units within the experimental errors. Unlike CMCs, as the ion content increased, partitioning of pyrene between the hydrophobic aggregates and an aqueous media decreased from 1.5 ×105 to 9.4 ×104. As the temperature increased from 10 to 80 °C, the values of CMCs increased less than one order of magnitude. While, the partition coefficients of pyrene decreased one order of magnitude and the effect of the ion content became negligible.
Structural and Compositional Evolution of Self-Assembled Germanium Islands on Silicon (001) During High Growth Rate LPCVD
Authors: Dilliway Gabriela D.M. , Cowern Nicholas E.B. , Jeynes Chris , O'Reilly Lisa , McNally Patrick J. , Bagnall Darren M.
Published: June 2019

Understanding the process of self-organization of Ge nanostructures on Si with controlled size distribution is a key requirement for their application to devices. In this study, we investigate the temporal evolution of self-assembled islands during the low pressure chemical vapour deposition (LPCVD) of Ge on Si at 650°C using high growth rates (6–9 nm/min). The islands were characterized by atomic force microscopy, transmission electron microscopy, Rutherford backscattering spectrometry and micro-Raman spectroscopy. We found that the first nanostructures to assemble were small islands, with a narrow size distribution, typical of the ‘lens-shaped’ structures reported in previous studies. Next to form were a population of larger ‘lens-shaped’ islands with a similar surface density to that of the small islands, but with broad height and width distributions. These islands differ from the pyramid-shaped islands previously reported for a similar size range. On further Ge deposition, the population evolves into one of large square-based truncated pyramids with a very narrow size distribution. Such pyramidal structures were previously reported at smaller sizes. Furthermore, we see no evidence of the multifaceted domes previously reported in this size range. The small ‘lens-shaped’ islands appear to be strained, whilst some of the intermediate-sized islands and all the large truncated pyramids contain misfit strain relaxation induced defects. Additionally, in the both the intermediate size ‘lens-shaped’ islands and in the large size truncated pyramidal islands, there is evidence of Si-Ge strain-induced alloying, more significant in the first than in the latter. Our observation of ‘lens shaped’ islands and truncated pyramids at larger sizes than are normally observed, suggests a kinetically driven process that delays the evolution of energetically favourable island structures until larger island sizes are reached.
ESR Study of Electrochemically Doped Chalcogenide Nanotubes
Authors: Arcon Denis , Zorko Andrej , Cevc Pavel , Mrzel Ales , Remskar Maja , Mihailovic Dragan , Dominko Robert , Gaberscek Miran
Published: June 2019

Electrochemical activity of differently pretreated single-wall subnanometer-diameter molybdenum disulfide tubes (nMoS2) was tested and compared with layered MoS2 material. In as prepared and de-iodized nMoS2 samples a significant increase in the charge capacity has been found compared to the one measured in dispersed nMoS2 or layered MoS2. Enhanced electrochemical activity has been attributed to a particular one-dimensional topology of nanotubes bundles. Electrochemically doped samples were then studied with X-band ESR. While undoped nMoS2 show no X-band ESR signal between room temperature and 4 K we found in heavily doped nMoS2 samples two distinct ESR components: a narrow component with a linewidth of few Guass and a broad component with a linewidth of more than 800 G. The broad ESR component is characteristic of Mo d-orbital-derived band. The temperature dependence of the ESR spin susceptibility and the linewidth of the broad ESR component can be discussed either in terms of conducting electrons coupled to defects or in terms of random-exchange Mo Heisenberg chain model.
Optimal Annealing Conditions of InGaAs Films for Selective Area Epitaxy of Quantum Dots by Indium Segregation
Authors: Yeoh Terence S. , Swint Reuel B. , Elarde Victor C. , Coleman James J.
Published: June 2019

The surface of strained InGaAs films on GaAs for selective regrowth of InAs nanostructures is investigated by atomic force microscopy and Rutherford backscattering. Various InxGa1-xAs films were annealed at temperatures between 400°C - 800°C. Significant indium desorption was found to occur at temperatures above 550°C.
Electron Microscopy Study of Submicron Size Antiferromagnetic KMnF3 Nanoparticles and Their Self-assembly
Authors: Anderson Jeffrey , Garcia Rubi , Zhou Weilie L.
Published: June 2019

Submicron KMnF3 cubic and spherical nanoparticles were synthesized using the reverse micelle method. The nanostructures of the nanocrystals were studied by field emission electron microscopy and transmission electron microscopy. KMnF3 nanocrystals synthesized at room temperature started with cubic submicron particles (∼100 nm) and consisted of KMnF3 nanocrystallites (10-15 nm). As the reaction continued, the nanocrystals fused together and transformed into perfect cubic nanocrystals. Spherical beads composed of KMnF3 nanocrystallites were observed at low temperature synthesis. As the reaction continued, the spherical particles grew larger, however, no characteristic cubic shape of KMnF3 nanoparticles were observed. Even as they grew larger, there was no evidence of homogeneous crystal morphology as seen in the room temperature samples. Cubic shape KMnF3 nanocrystals were self-assembled into large area self-assembling patterns.
Parallel Bias-Enhanced Sulfur-Assisted Chemical Vapor Deposition of Nanocrystalline Diamond Films
Authors: Jesùs Joel De , Gonzàlez Juan A. , Ortiz Oscar O. , Weiner Brad R. , Morell Gerardo
Published: June 2019

The transformations induced by the application of a continuous bias voltage parallel to the growing surface during the sulfur-assisted hot-filament chemical vapor deposition (HFCVD) of nanocrystalline diamond (n-D) films were investigated by Raman spectroscopy (RS), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The films were deposited on molybdenum substrates using CH4, H2 and H2S. Bias voltages in the range of 0 – 800 VDC were applied parallel to the substrate surface continuously during deposition. The study revealed a significant improvement in the films' density and a lowering in the defect density of the nanocrystalline diamond structure for parallel bias (PB) voltages above 400V. These high PB conditions cause the preferential removal of electrons from the gaseous environment, thus leading to the net accumulation of positive species in the volume above the growing film, which enhances the secondary nucleation. The nanoscale carbon nuclei self-assemble into carbon nano-clusters with diameters in the range of tens of nanometers, which contain diamond (sp3-bonded C) in their cores and graphitic (sp2-bonded C) enclosures. Hence, the observed improvement in film density and in atomic arrangement appears to be connected to the enhanced presence of positively charged ionic species, consistent with models which propose that positively charged carbon species are the crucial precursors for CVD diamond film growth.
Diffusion Mechanism for Self Assembly on Inhomogeneously Strained Surfaces
Authors: Larsson M.I. , Sabiryanov R.F. , Cho K. , Clemens B.M.
Published: June 2019

Growth of nanostructures with controlled shape, on inhomogeneously strained surfaces, is investigated by means of kinetic Monte Carlo (KMC) simulations. We propose a method to assemble self organized sub-lithographic nanostructures. The method is based on a strain-assisted mechanism for adatom surface diffusion and nucleation. For an inhomogeneous surface strain field there is normally a driving force toward the most tensile strained areas. It is shown by means of KMC simulations, that almost straight and continuous Ag nanowires can be produced on the Pt(111) surface if the growth is followed by high-temperature annealing. We suggest also how the method can be utilized as the first step of a process to reduce the circuit line width.
Controlling 2-Dimensional Growth of Silver Nanoplates
Authors: Chen Sihai , Carroll David L.
Published: June 2019

After the successful synthesis of silver nanoplates with shapes of truncated triangle and disk applying a seed-mediated growth process using cetyltrimethylammonium bromide as a shape controller, we here further report the method for systematic control of the size of silver nanoplate in 2-dimensions. Two ways are found effective in size control: one is through the change of the silver seed amounts, which can produce the nanoplates with the size varying from 210 nm to 40 nm; another is through the mild aging of the as-prepared silver nanoplate solution at a proper temperature, which can fine-tune the shape of the nanoplates, such as from triangle to circle, or from plate to sphere. X-ray and electron diffraction analysis reveal that these nanoplates are single crystals and with their basal plane as (111) planes. The in-plane dipole plasmon band of these nanoplates can thus be manipulated within 900 nm to 400 nm, providing new possibilities for applications in the fields such as infrared absorption, nonlinear optical limiting, and Raman or biochemical diagnosis.
Production of Nanostructures Under Ultraturbulent Collision Reaction Conditions - Application to Catalysts, Superconductors, CMP Abrasives, Ceramics, and Other Nanoparticles
Authors: Gruverman Irwin J. , Thumm Jeffrey R.
Published: June 2019

The development, operation and applications of a novel continuous chemical reactor system are described. The system, known as a Multiple Stream Mixer/Reactor (or MMR), produces nanoparticles by direct precipitation from two or more reactant solution streams in an extreme energy density, ultraturbulent, collision reaction region. Sensors and a control system are employed to assure constant mixing conditions and desired stoichiometry in the reaction region. The interaction chamber is designed to allow macro-, meso- and micromixing during processing. This allows control of product purity, yield, size, size distribution, and phase purity. Typical nanoparticle diameters in the one to ten nanometer range are often achievable, with tight size distribution. The MMR can be scaled from development quantities to tons/hour for production applications.
Synthesis of CdO Nanoneedles for Photonic and Sensing Applications
Authors: Liu Xiaolei , Li Chao , Han Song , Zhou Chongwu
Published: June 2019

Single-crystalline needle-shaped CdO nanostructures were synthesized using a chemical vapor deposition method and characterized using a variety of techniques. Devices consisting of individual CdO nanoneedles were fabricated and high conductance as well as high carrier concentrations was observed. The temperature dependence of the conductance revealed thermal excitation as the dominating transport mechanism. Our devices exhibited good sensitivity to both infrared light and diluted NO2 gas, indicating potential applications as infrared photo-detectors and toxic gas sensors.
Controlled Growth and Electronic Properties of Gallium Nitride Nanowires
Authors: Han Song , Jin Wu , Tang Tao , Li Chao , Zhang Daihua , Liu Xiaolei , Zhou Chongwu
Published: June 2019

High-quality single crystalline gallium nitride (GaN) nanowires are synthesized via a chemical vapor deposition (CVD) method using gold nanoparticles as the catalyst. This method enables control over several important aspects of the growth, including control of the nanowire diameter by using mono-dispersed gold clusters, control of the nanowire location via e-beam patterning of the catalyst sites, and control of the nanowire orientation via epitaxial growth on aplane sapphire substrates. Transport properties of these GaN nanowires are studied. Our work opens up new ways to use GaN nanowires as nano-building blocks.
The MrgA Multimeric Complex: a self-assembled nanostructure for inorganic synthesis
Authors: Kramer Ryan M. , Loganathan Amritraj G. , Naik Rajesh R. , Stone Morley
Published: June 2019

Utilization of protein cages in biomimetic chemistry allows for the deposition of inorganic materials within an organic construct, controlling the size and amount of material deposited within a constrained reaction environment. Previously, protein cages such as viral capsids and ferritins have been used in the constrained synthesis of inorganic materials. The MrgA protein displays a high sequence homology to both bacterial DNA-protecting proteins (Dps) found in many bacterial genera and Ferritin-like proteins (Flp), which have been shown to functionally sequester and store iron in a biologically available form. Here we demonstrate recombinant production, purification and characterization of the MrgA protein and provide evidence that this protein self-assembles to form a multimeric complex. This complex demonstrates characteristics similar to that of ferritin-like proteins such as resistance to iron toxicity, iron incorporation, and resistance to thermal and chemical denaturation. The ability to deposit iron within the putative internal cavity of this protein cage will allow the MrgA complex to be utilized as a spatially constrained reaction vessel for nanomaterial synthesis of other inorganic materials. From a materials science perspective, it will be interesting to see if these organic/inorganic hybrid materials can be harnessed for catalysis, nanomagnetics, and other applications.
Luminescence and Microstructure of Microspheres Containing Silicon Nanocrystals
Authors: Ryan C.A. , Meldrum A. , White C.W.
Published: June 2019

The strong visible photoluminescence (PL) of silicon nanocrystals has recently been the focus of considerable research interest. Nanocrystal composites produced by silicon implantation of a fused silica wafer followed by high-temperature thermal processing are characterized by a strong, broad photoluminescence spectrum. This light emission, centered in the near infrared and extending well into the visible range, has potential applications for the development of photonic materials based on silicon nanostructures. Here, we report on our attempts to form luminescent silica microspheres containing embedded silicon nanocrystals. Arrays of luminescent microspheres were successfully fabricated, without significant coagulation or destruction of the silica spheres during the silicon ion implantation step. However, a substantial deformation on the surface of the spheres that occurred during the high-flux implantation prevented the development of resonant cavity modes in the luminescence spectra. Resonant modes could clearly be observed for pre-implanted and annealed SiO2wafers with a layer of pristine microspheres subsequently deposited on the implanted surface. These results suggest an alternative method for producing highly durable luminescent silica “microbeads”. At lower ion fluxes, the development of luminescent microsphere superlattices with novel optical properties due to coupling of the light emission from the silicon nanocrystals into the resonant cavity modes may be possible if the deformation effects can be reduced or eliminated.
Ion Implantation Synthesis and Characterization of Cobalt Nanodots
Authors: Jacobsohn L.G. , Hawley M.E. , Dickerson R.M. , Cooke D.W. , Nastasi M.
Published: June 2019

A study of the synthesis of Co nanodots by ion implantation was carried out. Silica was implanted with 35 keV Co+ ion beams with doses of 8×1015, 3×1016 and 1×1017 at/cm2 and transmission electron microscopy revealed the presence of spherical nanodots in these samples. Annealing in vacuum at 900 oC was used to change the size distribution of the nanodots. The annealed samples presented an absorption band related to the plasmon collective excitation of the metallic nanodots that redshifted for higher Co contents. The magnetic character of the samples was revealed by magnetic force microscopy measurements that showed the presence of randomly distributed structures with defined magnetization in the case of annealed samples. This work shows the feasibility of synthesizing Co nanodots with controlled size distribution.
A Parametric Study of a Repository Tunnel for Decommissioning Waste
Authors: Pereira António C. , Sundström Benny , Broed Robert L.
Published: June 2019

The development of a radionuclide transport model for a tunnel of a repository for short-lived low and intermediate level waste is presented in this work. The model is two-dimensional and uses the finite element method to describe a cross-section perpendicular to the tunnel's main axis. It is shown that the use of a realistic geometry of the system, albeit in 2D, results in a transparent model that can handle the equations in a flexible way. The geometry can easily be changed and also extended to a 3D representation without affecting the numerical code. The disadvantage is the computational requirement. It is expected however that radionuclide transport modelling will evolve to 2D or 3D representations that are more realistic and transparent than today's 1D analytical models which involve many simplifications whose impact on the output is difficult to evaluate.
Use of Computational Thermodynamics in Rapid Prototyping and Infiltrating Steel Parts
Authors: Kernan Brian D. , Sachs Emanuel M. , Allen Samuel
Published: June 2019

The direct manufacture of metal parts by rapid prototyping often involves building a porous skeleton from a metal powder. In this work, a method termed Homogeneous Steel Infiltration has been developed for infiltrating steel skeletons to make conventional tool steel alloys. The method uses a gated infiltration route that uses as the infiltrant a steel alloy with a lower melting point than the base powder. The infiltrant liquid may use carbon and/or silicon as a melting point depressant. Premature freeze-off of the steel infiltrant is avoided by operating at a temperature where some liquid is stable at chemical equilibrium. The compositions of the skeleton and infiltrant and the infiltration temperature are selected by using computational thermodynamics. Examples of successful infiltrations using D2 and A3 tool steels as target compositions are shown. The thermodynamic design method enables suitable parameters to make other tool steels, some stainless steels and manganese steels.
N+/P and P+/N Junctions in Strained Si on Strain Relaxed SiGe Buffers: the Effect of Defect Density and Layer Structure
Authors: Eneman G. , Simoen E. , Delhougne R. , Verheyen P. , Ries M. , Loo R. , Caymax M. , Vandervorst W. , Meyer K. De
Published: June 2019

The electrical performance of junctions in SiGe Strain Relaxed Buffers (SRB's) with a strained Si top layer is investigated. Most of the SRB's grown in this experiment use a thin C-doped SiGe layer, which allows to fabricate thin (∼250nm) SRB's with a high relaxation degree. The effects of Threading Dislocation Density (TDD) and C-rich layer depth on the electrical behaviour of n+/p and p+/n junctions are studied. The C atoms in the junction's Space Charge Region (SCR) give rise to defects and induce a noticeable increase in the leakage. The effect of the TDD on the leakage in n+/p junctions is linear over the complete voltage range applied, while for p+/n junctions, only a small effect on leakage is measured at V=1V reverse for TDD's below 1×107cm-2. For low reverse voltages, the current varies more linearly with TDD.
Defect Characterization of CdTe Bulk Crystals Doped with Heavy Elements and Rare Earths
Authors: Neretina Svetlana , Sochinskii N.V. , Mascher Peter , Saucedo E.
Published: June 2019

The doping level in Cadmium Telluride (CdTe) is of the utmost importance for many applications. In this work, we have characterized CdTe crystals doped with Tl, Bi, or Yb as well as a crystal co-doped with Ge and Yb. The crystals were characterized using low-temperature Photoluminescence (PL), Positron Lifetime Spectroscopy (PLS), resistivity and a terahertz pump-probe technique that can determine carrier lifetimes. The properties of the crystals were also studied before and after a rapid thermal anneal (RTA) as well as after a longer conventional anneal. The results obtained using the various dopants vary widely. It will be shown, however, that the above mentioned dopants can form complexes with Cd vacancies (vacancy-impurity pairs). As a result, these Cd vacancies can play a key role in determining the resistivity and carrier lifetimes.
Device Parametric Shift Mechanism Caused by Boron Halo Redistribution Resulting from Dose Rate Dependence of SDE Implant
Authors: Jeong Ukyo , Liu Jinning , Guo Baonian , Shim Kyuha , Mehta Sandeep
Published: June 2019

Change in dopant diffusion was observed for Arsenic source drain extension (SDE) implants when they were performed at various dose rates. The high dose SDE implant amorphizes the surface of the silicon substrate and the thickness of the amorphous layer is strongly influenced by the rate of dopant bombardment. It is well known that the ion implantation process introduces excess interstitials. While the amorphous region is completely re-grown into single crystal during subsequent anneal without leaving behind extended defects, interstitials that are injected beyond the amorphous layer lead to formation of {311} defects or dislocation loops in the end of range region. During thermal processing, these extended defects dissolve, release interstitials, which in turn lead to transient enhanced diffusion of underlying Boron halo dopant. Dopant depth profiles measured by SIMS revealed different amount of Boron pile-up in the near surface region, corresponding to different SDE implant dose rates. In CMOS devices, this surface pile-up would correlate with a Boron pile-up in the channel region that would lead to a shift in transistor characteristics. Through this investigation, we were able to explain the mechanism causing device characteristics shift resulted from SDE implant with the same dose and energy but different dose rates.
Direct Measurement of Ion Beam Induced, Nanoscale Roughening of GaN
Authors: Cui Bentao , Cohen P. I. , Dabiran A. M.
Published: June 2019

Abatract

The formation of ion induced nanoscale patterns such as ripple, dots or pores can be described by a linear continuum equation consisting of a surface roughening term due to curvature-dependent sputtering or asymmetric attachment of vacancies, and a surface smoothing term due to thermal or ion-induced diffusion. By studying ion-induced dimple volume change using atomic force microscopy, we show a method to measure the ion-roughening coefficient. Using this method, we found the roughening coefficient í was 45 nm2/sec at 730K for initial ion etchings with 300 eV Argon ions. Cathodoluminescence measurements indicated Ga-vacancy formation during ion bombardment. The activation energy for surface relaxation after ion etching was about 0.12 eV as measured by reflection high energy electron diffraction.