747 research outputs found
Room temperature self-assembly of mixed nanoparticles into complex material systems and devices
The ability to manufacture nanomaterials with complex and structured
composition using otherwise incompatible materials increasingly underpins the
next generation of technologies. This is translating into growing efforts
integrating a wider range of materials onto key technology platforms1 - in
photonics, one such platform is silica, a passive, low loss and robust medium
crucial for efficient optical transport2. Active functionalisation, either
through added gain or nonlinearity, is mostly possible through the integration
of active materials3, 4. The high temperatures used in manufacturing of silica
waveguides, unfortunately, make it impossible to presently integrate many
organic and inorganic species critical to achieving this extended
functionality. Here, we demonstrate the fabrication of novel waveguides and
devices made up of complex silica based materials using the self-assembly of
nanoparticles. In particular, the room temperature fabrication of silica
microwires integrated with organic dyes (Rhodamine B) and single photon
emitting nanodiamonds is presented.Comment: Key words: nanotechnology, nanoparticles, self-assembly, quantum
science, singel photon emitters, telecommunications, sensing, new materials,
integration of incompatible materials, silica, glass, breakthrough scienc
Room-temperature fabrication of mono-dispersed liquid crystalline shells with high viscosity and high melting points
We propose a new method to fabricate mono-dispersed liquid crystalline (LC) microcapsules with shells consisting of LC materials showing high viscosity and/or high melting points at room temperature. In this method, it is important to control the state of the shell phase by the addition and removal of agents inducing LC-to-isotropic phase transitions and vice versa, respectively, at the right times.Reproduced from J. Mater. Chem. C , 2017, 5, 1303-1307 with permission from the Royal Society of Chemistry.https://doi.org/10.1039/c6tc05267
Room-temperature fabrication of high-resolution carbon nanotube field-emission cathodes by self-assembly
The room-temperature fabrication process of high-resolution carbon nanotube (CNT) field-emission cathodes by self-assembly was discussed. The well-defined patterns with variable thickness and less than a 10-μm linewidth were readily deposited. The CNTs were found to show long-range in-plane orientation ordering and adhered strongly to the substrates
Room-temperature fabrication of flexible thermoelectric generator using dry-spray deposition system
학위논문 (석사)-- 서울대학교 대학원 : 기계항공공학부, 2016. 2. 안성훈.We present a flexible thermoelectric (TE) generator with titanium dioxide (TiO2), antimony (Sb), and tellurium (Te) powders fabricated by a nanoparticle deposition system (NPDS). NPDS is a novel low-energy consumption dry-spray method that enables the deposition of inorganic materials on substrates at room temperature and under low vacuum. TiO2 nanopowders were dispersed on a TE powder for improved adhesion between TE films and the substrate. Film morphologies were investigated using field-emission scanning electron microscopy, and the phase structure was analyzed by X-ray diffraction. A TE leg, deposited with 3 wt% TiO2 content, had the largest Seebeck coefficient of approximately 160 µV/K. The prototype TE generator consisted of 16 TE legs linked by silver interconnects over an area of 20 × 60 mm2. The prototype produced a voltage of 48.91 mV and a maximum power output of 0.18 µW from a temperature gradient of 20 K. The values are comparable to that of conventional methods. These results suggest that flexible TE generators can be fabricated by energy efficient methods, although internal and contact resistances must be decreased.Chapter 1. Introduction 1
1.1 Background 1
1.2 Fabrication of flexible TE generators 2
1.3 Objectives 3
Chapter 2. Experimental procedure 4
2.1 Nano particle deposition system 4
2.2 Materials 6
2.3 TE generator fabrication process 7
2.4 Characterization 8
Chapter 3. Results and Discussion 9
3.1 Field-emission scanning electron microscopy 9
3.2 X-ray diffraction 11
3.3 Seebeck coefficient and internal resistance 12
3.4 Prototype flexible TE generator 13
3.5 Voltage and power output 14
3.6 Comparison with various fabrication methods 15
Chapter 4. Conclusions 17
Reference 18
Abstract (Korean) 20Maste
Enhanced Self-organized Dewetting of Ultrathin Polymer Films under Water-organic Solutions: Fabrication of Sub-micron Spherical Lens Arrays
Field-induced self-organized patterning in ultrathin (< 100 nm) polymer films
produces resolutions of the order of 10 {\mu}m or more because of the high
energy penalty for the surface deformations on small scales. We propose here a
very simple but versatile method to fabricate sub-micron (~100 nm) ordered and
tunable polymeric structures by self-organized room temperature dewetting of
ultrathin polystyrene films by minimizing the surface tension limitation. We
illustrate this technique by fabricating sub-micron lens arrays of tunable
curvature. This is achieved by switching to controlled room temperature
dewetting under an optimal mix of water, acetone and methyl-ethyl ketone (MEK).
Organic solvents used decrease the glass transition temperature, greatly
decrease the interfacial tension, intensify the field and increase the contact
angle/aspect ratio of the resulting tunable nano-structures, without a
concurrent solubilization of PS owing to water being the majority phase in the
outside mixture.Comment: 13 pages and 5 figure
Multistate resistive switching in silver nanoparticle films.
Resistive switching devices have garnered significant consideration for their potential use in nanoelectronics and non-volatile memory applications. Here we investigate the nonlinear current-voltage behavior and resistive switching properties of composite nanoparticle films comprising a large collective of metal-insulator-metal junctions. Silver nanoparticles prepared via the polyol process and coated with an insulating polymer layer of tetraethylene glycol were deposited onto silicon oxide substrates. Activation required a forming step achieved through application of a bias voltage. Once activated, the nanoparticle films exhibited controllable resistive switching between multiple discrete low resistance states that depended on operational parameters including the applied bias voltage, temperature and sweep frequency. The films' resistance switching behavior is shown here to be the result of nanofilament formation due to formative electromigration effects. Because of their tunable and distinct resistance states, scalability and ease of fabrication, nanoparticle films have a potential place in memory technology as resistive random access memory cells
Evanescent-wave coupled right angled buried waveguide: Applications in carbon nanotube mode-locking
In this paper we present a simple but powerful subgraph sampling primitive
that is applicable in a variety of computational models including dynamic graph
streams (where the input graph is defined by a sequence of edge/hyperedge
insertions and deletions) and distributed systems such as MapReduce. In the
case of dynamic graph streams, we use this primitive to prove the following
results:
-- Matching: First, there exists an space algorithm that
returns an exact maximum matching on the assumption the cardinality is at most
. The best previous algorithm used space where is the
number of vertices in the graph and we prove our result is optimal up to
logarithmic factors. Our algorithm has update time. Second,
there exists an space algorithm that returns an
-approximation for matchings of arbitrary size. (Assadi et al. (2015)
showed that this was optimal and independently and concurrently established the
same upper bound.) We generalize both results for weighted matching. Third,
there exists an space algorithm that returns a constant
approximation in graphs with bounded arboricity.
-- Vertex Cover and Hitting Set: There exists an space
algorithm that solves the minimum hitting set problem where is the
cardinality of the input sets and is an upper bound on the size of the
minimum hitting set. We prove this is optimal up to logarithmic factors. Our
algorithm has update time. The case corresponds to minimum
vertex cover.
Finally, we consider a larger family of parameterized problems (including
-matching, disjoint paths, vertex coloring among others) for which our
subgraph sampling primitive yields fast, small-space dynamic graph stream
algorithms. We then show lower bounds for natural problems outside this family
Controlling of Iridium Films Using the Proximity Effect
A superconducting Transition-Edge Sensor (TES) with low- is essential in
a high resolution calorimetric detection. With a motivation of developing
sensitive calorimeters for applications in cryogenic neutrinoless double beta
decay searches, we have been investigating methods to reduce the of an Ir
film down to 20 mK. Utilizing the proximity effect between a superconductor and
a normal metal, we found two room temperature fabrication recipes of making
Ir-based low- films. In the first approach, an Ir film sandwiched between
two Au films, a Au/Ir/Au trilayer, has a tunable in the range of 20-100
mK depending on the relative thicknesses. In the second approach, a
paramagnetic Pt thin film is used to create Ir/Pt bilayer with a tunable
in the same range. We present detailed study of fabrication and
characterization of Ir-based low- films, and compare the experimental
results to theoretical models. We show that Ir-based films with predictable and
reproducible critical temperature can be consistently fabricated for use in
large scale detector applications.Comment: 5 figures, accepted in the Journal of Applied Physic
Design, fabrication and characterization of a distributed Bragg reflector for reducing the étendue of a wavelength converting system
In this work, the design, fabrication and characterization are reported for a distributed Bragg reflector (DBR) filter with a specific wavelength and angular dependency, which aims to improve the light collection from a wavelength-converter-based light source into a smaller angle than the full angle Lambertian emission. The desired design is obtained by optimizing the transmission characteristics of a multi-layer structure. Titania (TiO2) and silica (SiO2) are used as high and low refractive index materials, respectively. The deposition is made by electron beam evaporation without substrate heating, followed by a post-annealing procedure. The optical properties of the evaporated layers are analyzed by ellipsometer and spectrometer measurements. The angular and wavelength dependency of the fabricated DBR is in good agreement with simulations for the designed structure. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen
- …