1,816 research outputs found
Structural reliability evaluation of low-k nanoporous dielectric interlayers integrated into microelectronic devices
No full textAs integrated microelectronic circuit device dimensions continue to shrink, low dielectric constant (low-k) interlayer dielectrics are required for minimizing RC signal delay, capacitive coupling noise, and power consumption. The implementation of low-k materials in an interconnected structure, however, is known to be a very difficult task because of many criteria imposed by the structural functionality and the integration process. Here, we report structural reliability evaluation for the integration of low-k nanoporous organosillicate dielectrics into a multilayer structure, involving capping, chemical mechanical polishing (CMP), post-CMP cleaning, and thermal annealing processes. We have successfully investigated the structural reliability of the low-k dielectric layer subjected to such harsh processes using synchrotron grazing incidence X-ray scattering and reflectivity (GIXS and XR) analyses. This study additionally demonstrated that synchrotron GIXS and XR techniques are very powerful tools for providing valuable, accurate insight into the nanopore structure in low-k dielectric thin layers and the structural changes with the integration process conditions.1133sciescopu
High-performance triazole-containing brush polymers via azide-alkyne click chemistry: a new functional polymer platform for electrical memory devices
No full textTwo series of well-defined brush polymers bearing a triazole moiety on each bristle were prepared from the click chemistry reactions of a poly(glycidyl azide) (PG) and a poly(4-azidomethylstyrene) (PS) with alkyne derivatives. The thin-film morphologies and properties, especially electrical memory performances, of these triazole-containing brush polymers were investigated in detail. The brush polymers with a triazole ring substituted with an alkyl or alkylenylphenyl group in the bristle exhibited only dielectric characteristics. By contrast, the other brush polymers bearing a triazole ring substituted with phenyl or its derivatives with a longer pi-conjugation length in the bristle demonstrated excellent unipolar permanent memory behaviors with low power consumption, high ON/OFF current ratios and high stability and reliability under ambient air conditions. Furthermore, their memory type could be tuned to p- or n-type by the incorporation of an electron-donating or -accepting group into the phenyl unit linked to the triazole moiety. Overall, this study presents the first demonstration of the azide-alkyne click chemistry synthesis of triazole moieties with substituent(s) that exhibit a resonance effect; this approach is a very powerful synthetic route to develop electrical memory polymers suitable for the low-cost mass production of high-performance, polarity-free programmable memory devices.111711Ysciescopu
Structural details and digital memory performances of difluorene-containing diblock copolymers in nanoscale thin films
No full textAmphiphilic poly(4-di(9,9-dihexylfluoren-2-yl)styrene)-b-poly(2-vinylpyridine)s (PStFl2(m)-b-P2VP(n)) in two different compositions and their homopolymers were synthesized: PStFl2(11)-b-P2VP(89) (50/50, volume ratio), PStFl2(12)-b-P2VP(33) (75/25), PStFl2, and P2VP. They were thermally stable up to around 350 degrees C. In nanoscale thin films, the diblock copolymers exhibited various phase-separated nanostructures depending on the composition and film process condition: random two phases, horizontal hexagonal P2VP cylinders, and hexagonally-close packed (HCP) P2VP spheres. Surprisingly, the hexagonal cylinder and HCP sphere structures are quite different from those of common diblock copolymers with similar compositions. The structural details of these thin film morphologies were investigated by synchrotron grazing incidence X-ray scattering. The thin film morphologies were found to make influences on the electrical memory performances of the polymers. In particular, the switching-ON voltage was influenced by the nanostructures and the film layer thickness as well as by the composition. Overall, the diblock copolymer films demonstrated excellent p-type permanent digital memory behaviors with unipolarity, long retention time, high ON/OFF current ratio and low power consumption. These memory behaviors were governed by a trap-limited space charge limited conduction mechanism combined with ohmic conduction and a hopping process. (C) 2015 Elsevier Ltd. All rights reserved.1134sciescopu
Hierarchical Self-Assembly and Digital Memory Characteristics of Crystalline-Amorphous Brush Diblock Copolymers Bearing Electroactive Moieties
No full textTwo series of crystalline amorphous brush diblock copolymers bearing electroactive moieties were newly synthesized by sequential anionic ring-opening copolymerizations of glycidyl derivatives and subsequent selective postfunctionalizations; their homopolymers and analogues were additionally synthesized. Self-assembly structural details and electrical memory behaviors of these polymers in nanoscale thin films were investigated. The diblock copolymers revealed complex hierarchical self-assembly structures depending on the compositions. The self-assembly structure and orientation of the crystalline block chains were severely affected by the geometrical confinement (i.e., size and shape) stemming from microphase separation. Such film morphologies were found to significantly influence the electrical properties; they exhibited electrical properties from p-type permanent memory behavior to dielectric-like behavior. The memory behaviors were governed by the trap-limited space charge limited conduction mechanism combined with ohmic conduction and the hopping paths composed of the electroactive moieties distributed locally.11108sciescopu
Clues to the Electrical Switching Mechanism of Carbazole-Containing Polyimide Thin Films
No full textThe mechanism behind electrical memory behavior of carbazole-containing polyimides (PIs) in nanoscale thin films was investigated. For this investigation, a series of poly(3,3'-dihydroxy-4,4'-biphenylene-co-3,3'-bis(N-ethylenyloxycarbazole)-4,4'-biphenylene hexafluoro-isopropylidenedi-phthalimide)s (6F-HAB-HABCZn PIs) with various compositions was synthesized as a model carbazole-containing polymer system. The thermal properties, band gaps, and molecular orbital levels of the PIs were determined. Furthermore, the chemical compositions, as well as the nanoscale thin film morphologies and electron densities, were analyzed, providing detailed information on the population and positional distribution of carbazole moieties in thin films of the PIs. PI Devices were fabricated with aluminum electrodes and tested electrically. The PI thin film layers in the devices exhibited electrically permanent memory behavior, which was driven by trap-limited space-charge limited conduction and ohmic conduction. The permanent memory characteristics were found to be attributed to the incorporated carbazole moieties rather than from the other chemical components. Furthermore, the memory characteristics depended significantly on the population and positional distribution of carbazole moieties in the PI layer, as well as the film thickness. Considering that the backbone is not conjugated, the present results collectively indicate that the electrical switching behavior of the PI films is driven by the carbazole moieties acting as charge traps and a hopping process using the carbazole charge-trap sites as stepping-stones.X111312sciescopu
New Fullerene-Based Polymers and Their Electrical Memory Characteristics
No full textCovalent incorporations into polymers of fullerene were achieved via the Cu(I)-catalyzed azide-alkyne click polymerizations of a fullerene derivative monomer functionalized with 5-(trimethylsilyl)pent-4-yn-1-yl groups and a comonomer functionalized with azidomethyl groups, producing the novel fullerene polymers P1-C60 and P2-C60. Despite their extremely high fullerene loading levels, the polymers were soluble in common organic solvents and exhibited no aggregation of fullerene units in films. Moreover, devices containing these fullerene polymers were easily fabricated with common coating processes that exhibit excellent unipolar and bipolar flash memory characteristics as well as unipolar permanent memory characteristics, with high ON/OFF current ratios, long retention times, and low power consumption. These electrical switching behaviors were favorably operated by electron injection. Overall, these devices are the first n-type bipolar and unipolar digital polymer memory devices which can be operated in flash and write-once-read-many-times modes.X111616sciescopu
Self-Assembly and Digital Memory Characteristics of an Oxadiazole-Containing Brush Polymer in Nanoscale Thin Films
No full textThe self-assembly characteristics in nanoscale thin films and digital memory behaviors of poly(5-phenyl-1,3,4-oxadiazol-2-yl-[1,1'-biphenyl]carboxyloxy-n-nonyl acrylate), a well-defined brush polymer bearing oxadiazole moieties, were investigated. The synchrotron grazing incidence X-ray scattering analysis found that the brush polymer molecules in thin films always formed a multibilayer structure consisting of fully extended backbone and bristle conformations. In the structure, the bristles were interdigitated in part; In particular, the oxadiazole containing mesogens were fully interdigitated via the pi-pi interaction of the biphenyl linkers. The multibilayer structured film undergoes three phase transitions (glass, melting, and liquid crystal-to-isotropic transitions) below the degradation temperature of 350 degrees C. The film's overall crystallinity, as well as the orientation of the multibilayer structure was found to depend on the film formation process conditions. While the as-cast films had a relatively low crystallinity and formed a vertical multibilayer structure with a broad orientation distribution, the thermally annealed films had a high crystallinity and formed an almost perfect horizontally oriented multibilayer structure. These different morphologies led different digital memory modes in devices; the as-cast films revealed volatile memory behavior, whereas the thermally annealed films showed permanent memory characteristics. These memory modes originated from the oxadiazole moieties in the two different film morphologies. The memory modes were demonstrated for the polymer films in the thickness range 5-50 nm.ungraded1133sciescopu
Self-assembly behaviours of a lipid-mimic brush polymer in thin films and at air-water interface
No full textSelf-assembly characteristics of poly(oxy(11-phosphorylcholineundecylthiomethyl) ethylene) (PECH-C-11-PC), a lipid-mimicking brush polymer, were investigated for the first time in nanoscale thin films as well as at the air-water interface using synchrotron grazing incidence X-ray scattering, X-ray reflectivity, and infrared spectroscopy. In thin films, the PECH-C11-PC molecules were found to form a well-ordered, in-plane-oriented molecular multibilayer structure in which the bristles made partial interdigitation in the neighbored layers via the favorable interactions of the PC end groups. The brush polymer molecules were further found to favorably form molecular assemblies at the water interface. They initially formed a monolayer assembly in which the hydrophilic backbones were in the extended conformation and the zwitterionic PC ends were anchored at the water interface and the hydrophobic alkylenyl linkers were present over the water surface. This phase underwent a surface pressure-driven structural transformation path way, ultimately forming a canonical bilayer structure similar to that commonly observed among natural lipids. These remarkable self-assembly behaviors were comprehended with consideration of the hydrophilic backbone, zwitterionic PC end, hydrophobic alkylenyl linker, and their selective interactions. (C) 2015 Elsevier Ltd. All rights reserved.1121sciescopu
Well-defined hollow nanochanneled-silica nanospheres prepared with the aid of sacrificial copolymer nanospheres and surfactant nanocylinders
No full textA new approach for synthesizing well-defined hollow nanochanneled-silica nanosphere particles is demonstrated, and the structural details of these particles are described for the first time. Positively charged styrene copolymer nanospheres with a clean, smooth surface and a very narrow size distribution are synthesized by surfactant-free emulsion copolymerization and used as a thermal sacrificial core template for the production of core-shell nanoparticles. A surfactant/silica composite shell with a uniform thickness is successfully produced and deposited onto the polymeric core template by charge density matching between the polymer nanosphere template surface and the negatively charged silica precursors and then followed by selective thermal decomposition of the polymeric core and the surfactant cylinder domains in the shell, producing the hollow nanochanneled-silica nanospheres. Comprehensive, quantitative structural analyses collectively confirm that the obtained nanoparticles are structurally well defined with a hollow core and a shell composed of cylindrical nanochannels that provide facile accessibility to the hollow interior space. Overall, the hollow nanochanneled-silica nanoparticles have great potential for applications in various fields.11118sciescopu
High-Performance n-Type Electrical Memory and Morphology-Induced Memory-Mode Tuning of a Well-Defined Brush Polymer Bearing Perylene Diimide Moieties
No full textPoly(N-(1-hexylheptyl)-N'-(12-oxydodecyl)perylene-3,4,9,10-tetracarboxyldi-imide acrylate) (PAcPDI), a perylene diimide (PDI) containing brush polymer, is synthesized, revealing good solubility in organic solvents, excellent thermal stability up to around 340 degrees C, and two melting transitions over 130-220 degrees C. The self-assembly and n-type memory characteristics of PAcPDI in nanoscale thin films are quantitatively investigated. As-cast films of PAcPDI are completely amorphous and the PDI units nevertheless formed p-p stacks favorably. However, the PAcPDI molecules can self-assemble via thermal annealing, developing a well-ordered horizontal lamellar structure with monomorphic or polymorphic monoclinic PDI crystals. The formation of monomorphic or polymorphic monoclinic crystals is attributed to various p-p stack modes of the PDI units, and is shown to be dependent on the film thickness. The differences in the thin film morphologies are directly reflected into the electrical memory behavior. The thermally annealed films demonstrate high-performance n-type unipolar volatile memory behavior within the thickness range of 12-31 nm. The as-cast films show n-type unipolar nonvolatile or volatile memory behavior in the range of 12-53 nm. The memory mode of PAcPDI films can be tuned by changing either the morphology or the film thickness.11117sciescopu
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