bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Microstructural Analysis of Benzylthiol-functionalized Au Nanocrystals
Authors: Vitale Floriana , Mirenghi Luciana , Piscopiello Emanuela , Protopapa Maria Lucia , Tapfer Leander , Giannini Cinzia , Guagliardi Antonietta , Cervellino Antonio , Pellegrini Giovanni , Trave Enrico , Mattei Giovanni , Mazzoldi Paolo , Fratoddi Ilaria , Russo Maria Vittoria 
Published: April 2011

ABSTRACTWe report on the synthesis and microstructural and microanalytical analysis of dodecanethiol and benzylthiol-stabilized Au nanoparticles (diameter range between 2 nm and 10 nm). Stable functionalized gold nanoparticles were synthesized by using two different routes: a two-phase liquid-liquid method and a one-phase method. The size, strain, shape and crystalline structure of the nanocrystals were determined by a full-pattern X-ray powder diffraction analysis and high-resolution electron microscopy. The chemical environment of the Au nanocrystals and their interaction with the thiols was investigated by X-ray photoelectron spectroscopy. Photoluminescence spectroscopy measurements show a characteristic IR emission at λ=960 nm of small sized Au nanocrystals (∼3 nm). The origin of this IR emission line seems to be correlated to the Au-S bonding and the size of the nanoparticles.
Iron Nanoparticles Embedded in Silica Glass: A Computational Study
Authors: Kroll Peter , Theuerkauf Jens , Wieland Thomas 
Published: April 2011

ABSTRACTWe performed electronic structure calculations within density functional theory including ab initio molecular dynamic simulations of isolated Fe13 and Fe55 clusters. We observed the energy preference of icosahedral clusters over cuboctahedrons for both Fe13 and Fe55. The magnetic structure is ferromagnetic for Fe13, but anti-ferromagnetic for Fe55. But isolated clusters exhibit a HOMO-LUMO gap.
Subsequently, we embedded the clusters into models of silica glass of different size. For embedded clusters we observed the formation of an iron oxide interface between cluster and dielectric matrix. Though many different models were computed, they show a very homogeneous trend. The magnetization of optimized embedded models is close or larger than the magnetization of free clusters. The small clusters retain their electronic structure around the Fermi-level despite some major distortions.
Thermodynamic Modeling of Island Size Distributions for InGaAs/GaAs Self Assembled Quantum Dots: A Quantitative Effort to Understand Ensemble Size Nonuniformity
Authors: Cederberg Jeff , Roshko Alexana , Hyland Brit , Coltrin Michael 
Published: April 2011

ABSTRACTExperimental island count histograms as a function of SAQD volume have been evaluated using an established model. The experimental data was obtained for 51 mm wafers grown by MOCVD and analyzed over the center 26 × 26 mm square of the wafer with AFM. More than one distribution is required for all conditions investigated to obtain adequate representations of the experimental data. Consistent parameters are obtained for samples grown with a variable InAs thickness. Higher growth temperatures results in material being converted into relaxed islands. Extended annealing without AsH3 eliminates small islands, suggesting that they are not a stable distribution.
Microscopical Study of Au Nanocrystals Self-Assembled on (100)Si and SiO2/(100)Si Substrates
Authors: Piscopiello Emanuela , Tapfer Leander , Vittori Antisari Marco , Paiano Pasquale , Prete Paola , Lovergine Nicola 
Published: April 2011

ABSTRACTThis work reports on the structural characterization of Au nanocrystals directly prepared on the surface of (100)Si and 150 nm-thick SiO2 deposited (100)Si substrates, by a physical self-assembly method, consisting in the UHV evaporation of a thin Au film and its successive high temperature annealing. The morphology, orientation, and crystalline structure of Au nanocrystals were characterized by scanning and high-resolution transmission electron microscopy and X-ray diffraction, respectively. Experimental results show that the nature of the substrate strongly influences the process of Au nanocrystal formation upon heat treatment, by affecting the interaction of deposited Au with the underlying material. In the case of clean (100)Si substrates the Au strongly interacts with Si, so that Au nanoislands are obtained with a well defined epitaxial relationships with the substrate, i.e. [100]AuÐÐ[110]Si and [110]AuÐÐ[311]Si. The nanoisland shape is affected by faceting at the Au/Si interface, the Au nanocrystal being limited by the {111}, {311}, {711} and {-111} planes of Si. In the case of SiO2/(100)Si substrates spherical shaped Au nanoparticles with random crystal orientation are instead, produced.
Tunnel QW-QDs InGaAs-InAs High Gain Medium for All-Epitaxial VCSELs
Authors: Tokranov Vadim , Yakimov Michael , van Eisden Jobert , Oktyabrsky Serge 
Published: April 2011

ABSTRACTStructures of tunnel-coupled pairs consisting of InGaAs (In composition was varied from 29 to 36%) quantum wells (QW) grown on top of shape-engineered self-assembled InAs quantum dots (QW-on-QDs) were employed to increase the maximum saturated gain of QD-based laser active medium. Room temperature optical properties of tunnel-coupled well-on-dots structures at low excitation were found to be sensitive to energy separation between GS energies of QDs and QW. The spectra also show that QD-related photoluminescence (PL) tends to peak at discrete energy separations from the QW peak, in this case multiples of ∼ 35meV (LO phonon energy). The optimized GS energy separation between QW and QDs was found to be close to the energy of the LO phonon. This structure demonstrated narrowing of the QD PL line down to 21.6 meV at T=77K, indicating efficient resonant tunneling of carriers from QW into QD ensemble states. All-epitaxial vertical cavity surface emitting lasers (VCSELs) with triple-pair tunnel QW-on-QDs as active medium demonstrated continuous wave mode lasing. Tunnel QDs-QW VCSELs exhibited 1.8 mA (Jth ∼ 800 A/cm2) minimum threshold current at QD GS emission wavelength, 1135 nm, with 0.7mW optical power and 12% light-current efficiency.
Multiple modes of laser-induced pattern formation in nanoscopic Co films
Authors: Favazza Christopher , Trice Justin , Sureshkumar Radhakrishna , Kalyanaraman Ramki 
Published: April 2011

ABSTRACTDewetting instabilities in nanoscopic Co films, induced by uniform multiple ns pulse laser irradiation, leads to a system of nanoparticles with robust spatial order. On the other hand, irradiation by non-uniform laser intensity, such as with a two beam laser interference pattern generates a quasi two-dimensional pattern of nanoparticles possessing long range order (LRO) and short range order (SRO). Here we discuss the various instabilities that are responsible for the production of these dissimilar patterns and length scales on the basis of their time scales. For the case of single beam irradiation, the film progresses in a manner that can be attributed to classical spinodal dewetting. Pattern formation from interference irradiation is the result of time scale-based selection of competing processes, which can be chosen by controlling the film thickness. This approach promises a simple and cost-effective means to self-assemble various nanostructures.
Vertically Aligned Carbon Nanotubes Growth Using Self-assembled Ni Nanoparticles Produced by Ion Implantation
Authors: Baptista D. L. , Lopes J. M. J. , Morschbacher M. J. , Dalal S. H. , Oei S. P. , Teo K. B. K. , Milne W. I. , Zawislak F. C. 
Published: April 2011

ABSTRACTAn alternative method for seeding catalyst nanoparticles for carbon nanotubes and nanowires growth is presented. Ni nanoparticles are formed inside a 450 nm SiO2 film on (100) Si wafers through the implantation of Ni ions at fluences of 7.5×1015 and 1.7×1016 ions cm−2 and post-annealing treatment at 700, 900 and 1100 °C. After exposed to the surface by HF dip etching, the Ni nanoparticles are used as catalyst for the growth of vertically aligned carbon nanotubes by direct current plasma enhanced chemical vapor deposition.
Novel Nanocarbons: Global Topology and Curvature Perspectives
Authors: Gupta Sanju , Saxena A. 
Published: April 2011

ABSTRACTCarbon nanotubes (both the single- and multi-walled), in the family of nanostructured carbons, are of great interest because of several unsurpassable physical properties and it needs to be shown that they are physically stable and structurally unaltered when subjected to radiation. In addition to testing them for space applications, when exposed to high energy electron beam from transmission electron microscopy, the results seem quite promising in terms of nano-engineering/ nano-manufacturing for producing novel nanocarbons [1-3]. Experimental studies of effects of electron beam irradiation on carbon nanotubes show that multi-walled ones tend to be relatively more robust than their single-walled kins. The increased exposure on an individual bundle of single-wall nanotubes promoted graphitization, pinching, and cross-linking analogous to polymers forming an intra-molecular junction (IMJ) within the area of electron beam focus, possibly through aggregates of amorphous carbon [2,3]. Formation of novel nanostructures (nano-ring and helix-like) due to irradiation are observed. These studies shed light on the dynamics of nanomanufacturing and a regime of possible relevance of these materials for: (i) short-term space missions; (ii) radiation hard programmable logic circuits; and (iii) radiation pressure sensors. It is suggestive that a local reorganization occurs. Through resonance Raman spectroscopy and related techniques we also elucidate an important notion of global topology and curvature at nanoscale which points to an emergent paradigm of Curvature/Topology → Property → Functionality in these technologically important geometries of carbons: nanotubes, fullerenes, nanorings, nanocones, nanohorns and nanodisks. To this end, we have determined the variation in first order high frequency Raman band which indicates a strong electron-phonon coupling. These concepts also apply to nanostructures of other “topological materials” such as BN nanotubes and nanotori, helical gold nanotubes as well as Möbius conjugated polymers.
Annealing Study of (Co/Pd)N Magnetic Multilayers for Applications In Bit-Patterned Magnetic Recording Media
Authors: Chunsheng E. , Rantschler James , Zhang Shishan , Lee T. Randall , Smith Darren , Weller Dieter , Khizroev Sakhrat , Litvinov Dmitri 
Published: April 2011

ABSTRACTThis work presents an annealing study of high-anisotropy (Co/Pd)N magnetic multilayers designed for bit-patterned medium recording applications. Magnetic multilayers were deposited by magnetron sputtering at 2.5mT argon pressure at room temperature and annealed at different temperatures (up to 250 °C) for up to 2 hours in atmosphere and in vacuum. Depending on the annealing time, the samples annealed in atmosphere exhibited two distinct modes of magnetization reversal. In samples annealed for a time shorter than some critical time, tc, where tc is a function of the annealing temperature, the magnetization reversal occurs by domain wall injection and propagation. In samples annealed for times longer then tc, the magnetization reversal mode switches to magnetization rotation. Using XPS, it is found that the transition is accompanied by the formation of oxidizes at the grain boundaries leading to exchange decoupling of the grains. In samples annealed at higher temperatures, the increases of the coercivity of as high as 30 times the coercivity of as prepared samples are observed. Significantly, annealing in vacuum showed only small modification of magnetic properties as manifested by relatively minor modifications of vertical M-H loops and unchanged morphology of domain patterns in AC demagnetized state.
Nanofabrications for Information Technology
Authors: Choi Kyung 
Published: April 2011

ABSTRACTSince industry has been seeking for advanced nanotechnology, development of new nano-materials and nanofabrication techniques has been a key contributor to satisfy our growing demands on miniaturization. This will present technological emergences in fabrications of novel optoelectronic devices by developing new materials since nanotechnology is a part of chemical domain. It will cover up as how chemists can contribute to this area to fabricate functional nanofabrications for information technology. For example, we developed a new class of PDMS stamps to overcome the limitations and thus to extend current soft lithography to advanced level for developing nanoscale-devices. Patterns fabricated using functional polymers also have many information technology applications to integrate optoelectronic devices.
Nanopatterning and Nanomachining with Table-top Extreme Ultraviolet Lasers
Authors: Marconi Mario , Wachulak Przemyslaw Wojciech , Capeluto Maria Gabriela , Vaschenko Georgyi , Bravo Herman , Menoni Carmen S , Rocca Jorge , Anderson Erik H , Chao Weilun , Attwood David , Hemberg Oscar , Frazer Bradley , Bloom Scott 
Published: April 2011

ABSTRACTNanopatterning and nanomachining of PMMA coated wafers was performed using table top extreme ultraviolet lasers. Features below 100 nm were imprinted with short (50-60 s) exposure times.
Replication of Grating-Based Optically Variable Devices in Polypropylene
Authors: Leech Patrick W. 
Published: April 2011

ABSTRACTThe hot embossing of grating-based optically variable devices has been demonstrated in biaxially-oriented polypropylene (BOPP). The embossing of several types of optically variable device has been examined including portrait, non-portrait and 3 dimensional images. The images embossed into BOPP have displayed a novel optically variable effect when viewed in transmitted light. Embossing of the grating structures was examined over a range of temperatures (80-155 °C) at 135 kN force. High quality replication was achieved over a full embossing area of 80 x 80 mm at temperatures > 120 °C.
Fabrication of Magnetic Nanostructures for MRAM using Electron Beam and Focused Ion Beam Exposure of HSQ
Authors: Chen Chen , Cabral Michael J , Hull Robert , Harriott Lloyd R 
Published: April 2011

ABSTRACTGiant magnetoresistive (GMR) materials-based magnetic random access memory (MRAM) has become attractive due to non-volatility, speed and density1. The vertical MRAM (VMRAM) design model shows good signal level and high speed and density potential. The memory cell for the VMRAM model is a ring shaped magnetic material multilayer, which ensures high repeatability and low switching energy. This GMR structure, however, is difficult to pattern as it contains materials such as Ni, Fe, Co, and Cu, which are difficult to dry etch because they lack volatile etch products. This work shows that it is possible to overcome the difficulties associated with etching GMR materials by using hydrogen silsesquioxane (HSQ) as an etch mask. We have used HSQ in a direct-write electron-beam lithography system with a dose of 600 μC/cm2, and in a Ga+ ion focused ion beam (FIB) system with a dose of 12 μC/cm2. Both are followed by development and an argon plasma etch at 10mTorr and 100W RIE power. The HSQ layer provides high resolution as well as good etching resistance. Electron-beam exposed HSQ shows a 1:1.5 selectivity over the GMR film stack and the FIB exposed HSQ showed an improved etch selectivity of 1:1. Ring shaped GMR structures with a 75/225 nm (ID/OD) have been fabricated, which corresponds to a memory density of 4Gb/in2.
Novel Anionic Photoacid Generators (PAGs) and Photoresists for sub 50 nm Patterning by EUVL and EBL
Authors: Wang Mingxing , Lee Cheng-Tsung , Henderson Clifford L , Yueh Wang , Roberts Jeanette M , Gonsalves Kenneth E 
Published: April 2011

ABSTRACTA new series of anionic photoacid generators (PAGs), and corresponding polymers were prepared. The thermostability of PAG bound polymers was superior to PAG blend polymers. PAG incorporated into the polymer main chain may improve acid diffusion compared with the PAG blend polymers, which was demonstrated by Extreme Ultraviolet lithography (EUVL) results: the fluorine PAG bound polymer resist gave 45 nm (1:1), 35 nm (1:2), 30 nm (1:3) and 20 nm (1:4) Line/Space as well as 50 nm (1:1) elbow patterned, showed better resolution than the blend sample.
Application of Novel Base Amplifiers with 3-Nitropentan-2-yl Group to Photoreactive Materials
Authors: Arimitsu Koji , Ito Yusuke , Gunji Takahiro , Abe Yoshimoto , Ichimura Kunihiro 
Published: April 2011

ABSTRACTIn order to enhance the photosensitivity of photoreactive materials utilizing base-catalyzed reactions, we developed base amplifiers that decompose autocatalytically to generate newborn amine molecules. Actually, we reported that the addition of base amplifiers to the photoreactive materials such as photoresists and UV-curing materials resulted in the marked improvement photosensitivity. However, conventional base amplifiers have aromatic rings such as fluorenyl groups and phenyl groups. Consequently, these base amplifiers have strong absorption of UV light which is a trigger of photolysis of a photobase generator. This leads to the hindrance of the photolysis. We report here novel base amplifiers with 3-nitropentan-2-yl group which has no aromatic rings.The base amplifiers decomposed autocatalytically to generate newborn amine molecules at an elevated temperature in solution and a polystyrene film in the presence of a catalytic amount of amines. Moreover, combining the base amplifiers with UV-curing materials consisting of a photobase generator and liquid epoxy resins resulted in the improvement of curing efficiency. To apply the base amplifier to photopatterning materials, we synthesized novel silicone resins with 3-nitropentan-2-yl groups as base-amplifying polymers. A film of the resin decomposed autocatalytically to generate amino groups in its side chains at an elevated temperature in the presence of a catalytic amount of amines. Furthermore, we demonstrated that the resins sensitized with a photobase generator provided negative- and positive-working photopolymers in the following ways. A thin film of the resin containing 10 wt% of a photobase generator became soluble in an acidic aqueous solution after 254 nm light irradiation of an exposure dose of 1 mJ/cm2 and subsequent baking at 50 oC for 20 min. This is because of formation of amino groups in its side chains. On the other hand, the film became insoluble in organic solvents after 254 nm light irradiation of an exposure dose of 1 mJ/cm2 and subsequent heat treatment at 50 oC for 40 min, this arises from that the photobase-catalyzed hydrolytic condensation of residual ethoxysilyl units of the resin proceeded to form crosslinked networks.
Photoimaging Materials Based on Base-amplifying Silicone Resins Having Phenylsulfonylethyl Groups
Authors: Inoue Satoru , Arimitsu Koji , Gunji Takahiro , Abe Yoshimoto , Ichimura Kunihiro 
Published: April 2011

ABSTRACTRecently, the large number of investigations concerning acid-catalyzed photopolymer systems such as chemically amplified photoresists and UV-curing materials has been reported. On the other hand, analogous systems utilizing base-catalyzed reactions have received far less attention, because low quantum yields for photobase generation to lead to low photosensitivity of these systems. To improve this problem, we proposed introduction of the concept of base proliferation reactions into the photopolymer systems using base-catalyzed reactions. The concept involves the autocatalytic base-catalyzed decomposition of a compound, referred to as a base amplifier which releases a newborn amine, leading to its autocatalytic decomposition. In fact, the addition of the base amplifiers such as 9-fluorenylmethyl carbamate, phenylsulfonylethyl carbamate, and 3-nitropentane-2-yl carbamate to a photopolymer consisting of an epoxy polymer sensitized and a photobase generator (PBG) resulted in the marked improvement of photosensitivity.However, these base amplifiers with low molecular weight are not suitable for photopatterning because of the volatility and the excessive diffusion of amines proliferated in polymer films. We report here novel base-amplifying silicone resins tethering phenylsulfonylethyl carbamoyl groups which proliferate primary amino groups or secondary amino groups in their side chains.Base-catalyzed decomposition behavior of films of these resins containing PBG was evaluated by UV absorption measurements. A film consisting of the resin proliferating primary amino groups and 10 wt% of PBG decomposed immediately in a nonlinear manner by 365 nm irradiation and subsequent heat treatment at 120oC for 6 min. On the other hand, this film without UV irradiation was thermally stable for 18 min at 120oC. These results indicate that photoinduced base proliferation reaction of the resin proceeded. A film consisting of the resin generating secondary amino groups and PBG decomposed in a way similar to that of the resin proliferating primary amino groups. Furthermore, lithographic evaluation of the film comprising the resin to generate secondary amines and PBG obtained 7ÊS positive images with an exposure dose of 75 mJ/cm2 which shows higher sensitivity when compared to conventional base-catalyzed photopolymers.
Modeling Evaporation Driven Self-Assembly Systems for Magnetic Storage Arrays
Authors: Dyreby John , Nellis Greg F. , Turner Kevin T. 
Published: April 2011

ABSTRACTA modeling methodology based on computational fluid dynamics (CFD) has been developed that is appropriate for the global regime of lithographically directed, evaporation driven self-assembly. The modeling technique has been experimentally verified through comparison with the well-known benchmark case of evaporation driven self-assembly associated with the evaporation of a colloidal, self-pinned droplet. The predicted evolution of the particle distribution during evaporation is compared to optical experimental measurements of the particle distribution within an evaporating droplet containing fluorescing nanoparticles.
Massively Parallel Scanning Probes Microscope with Digital Holographic Readout
Authors: Sache Laurent , Bleuler Hannes 
Published: April 2011

ABSTRACTMassively Parallel Scanning Probe Microscopy is an obvious path for enhancing the acquisition speed and the imaging range of current based-AFM metrology devices. Current experimental systems, based on active probes array, would reach their limits in density and hardware complexity. This paper presents a new approach with the promise to break several of these barriers. The key idea is readout of a Scanning Probes Microscope (SPM) array by an interferometer technique called digital holography which directly gives the cantilever phase information at each pixel of a CCD array. This means that no contact line to each individual SPM probes is needed, allowing us to reach very high density of probes. The phase information is available in a parallel form in real-time. Moreover, the digital holography optical setup (Digital Holography Microscope or DHM) needs in principle no expensive components, optical (or, to a large extent, mechanical) imperfections being compensated in the signal processing, i.e. in electronics. This gives the system the potential for a low cost device with fast and large readout capability.