Assembly and Optical Properties of Metal Nanoparticles

2019 ◽  
Vol 294 ◽  
pp. 3-10
Author(s):  
E.A. Dawi ◽  
A. Abdelkader
Keyword(s):  
Gold Nanoparticles ◽  
Optical Properties ◽  
Self Assembly ◽  
Silicon Oxide ◽  
Ex Situ ◽  
Visible Range ◽  
Plasmonic Nanostructures ◽  
Electromagnetic Spectrum ◽  
Force Microscopy ◽  
Atomic Force

In this paper, the deposition and optical properties of charge-stabilized gold nanoparticles on silicon oxide substrates is studied, which have been derivatised with (aminopropyl) triemethoxysilane. Monodispersed charged-stabilized colloidal gold nanoparticles with diameters between 20-150 nm were prepared and their self-assembly and optical properties on silica substrates is studied. Atomic force microscopy (AFM) is employed to investigate the nanoparticle monolayers ex situ. Analysis of AFM images provide evidence that the formation of the colloidal nanoparticle monolayers is governed by random sequential adsorption. The results indicate that the ionic strength of the suspension influences the spatial distribution of the nanoparticles. For all sizes of the Au nanoparticles tested, optical simulations of extinction coefficients made by finite-difference time domain (FDTD) indicate a resonance peak in the range of 510-600 nm wavelength of the visible range of the electromagnetic spectrum. The results indicate a simple and inexpensive approach of assembly of plasmonic nanostructures that can find applications in metamaterials and light waveguides.

Nanoindentation Assisted Self-Assembly of Quantum Dots

2006 ◽  
Author(s):  
Curtis Taylor ◽  
Eric Stach ◽  
Gregory Salamo ◽  
Ajay Malshe
Keyword(s):  
Quantum Dots ◽  
Self Assembly ◽  
Surface Strain ◽  
Ex Situ ◽  
Atomic Step ◽  
Uniform Size ◽  
Force Microscopy ◽  
Atomic Force ◽  
And Performance ◽  
Spatial Positioning

The ability to pattern quantum dots with high spatial positioning and uniform size is critical for the realization of future electronic devices with novel properties and performance that surpass present technology. This work discusses the exploration of an innovative nanopatterning technique to direct the self-assembly of nanostructures. The technique focuses on perturbing surface strain energy by nanoindentation in order to mechanically bias quantum dot nucleation. Growth of InAs quantum dots on nanoindent templates is performed using molecular beam epitaxy (MBE). The effect of indent spacing and size on the patterned growth is investigated. The structural analysis of the quantum dots including spatial ordering, size, and shape are characterized by ex-situ atomic force microscopy (AFM). Results reveal that the indent patterns clearly bias nucleation with dot structures selectively growing on top of each indent. It is speculated that the biased nucleation is due to a combination of favorable surface strain attributed to subsurface dislocation strain fields and/or multi-atomic step formation at the indent sites, which leads to increased adatom diffusion on the patterned area.

Mechanically Biased Self-Assembly of Quantum Dots by Nanoindentation

2006 ◽  
Vol 921 ◽  
Author(s):  
Curtis R. Taylor ◽  
Ajay Malshe ◽  
Eric Stach ◽  
Euclydes Marega ◽  
Gregory Salamo
Keyword(s):  
Quantum Dots ◽  
Self Assembly ◽  
Surface Strain ◽  
Ex Situ ◽  
Atomic Step ◽  
Inas Quantum Dots ◽  
Force Microscopy ◽  
Patterned Growth ◽  
Atomic Force ◽  
Cube Corner

AbstractNanoindentations were created in the GaAs(100) surface to act as strain centers to bias the nucleation of self-assembled InAs quantum dots providing for patterned growth. Indents were generated using loads below 450 μN with a sharp cube corner indenter. Growth of InAs quantum dots on indent patterns is performed using molecular beam epitaxy (MBE). The effect of indent spacing and size on the patterned growth is investigated. The structural analysis of the quantum dots including spatial ordering, size, and shape are characterized by ex-situ atomic force microscopy (AFM). Results reveal that the indent patterns clearly bias nucleation with dot structures selectively growing on top of each indent. It is speculated that the biased nucleation is due to a combination of favorable surface strain and multi-atomic step formation at the indent sites, which leads to increased adatom diffusion on the patterned area.

A Study on Structure and Optical Properties of Sputtered TiO2 Films

2014 ◽  
Vol 875-877 ◽  
pp. 223-227
Author(s):  
Mei Dong Huang ◽  
Shan Du ◽  
Hong Yu Li ◽  
Chun Wei Liu ◽  
Xiao Hong Tang
Keyword(s):  
Optical Properties ◽  
Optical Constants ◽  
Visible Range ◽  
X Ray Diffraction ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Argon Flow ◽  
Titanium Oxide Films ◽  
K9 Glass

Influence of argon flow on the optical properties of titanium oxide films, which were fabricated on well-polished K9 glass substrate through r.f. magnetron sputtering, has been investigated. X-ray diffraction (XRD) was employed to analyse the microstructure. Surface morphology was observed by atomic force microscopy (AFM). Transmittance of the films was measured within the visible range by UV-3600 spectrometer. The optical constants, such as thickness, refractive index and extinction coefficient, were measured using an ellipsometer. The experimental results and the effects of argon flow on optical constants of the TiO2films have been discussed and analysed.

Well-Ordered Self-Assembly Growth of Strain-Modulated SrTiO3 Thin Films: Templates for Complex Oxide Quantum Wires

2005 ◽  
Vol 475-479 ◽  
pp. 4255-4260 ◽  
Author(s):  
Yan Rong Li ◽  
Jin Long Li ◽  
Ying Zhang ◽  
Xin Wu Deng ◽  
Fan Yang ◽  
...  
Keyword(s):  
Compressive Stress ◽  
Self Assembly ◽  
Quantum Wires ◽  
Complex Oxide ◽  
High Energy ◽  
The Self ◽  
Ex Situ ◽  
Force Microscopy ◽  
Atomic Force ◽  
Self Assembled

Well-ordered self-assembled SrTiO3 thin film, as a template for complex oxide quantum wires, was fabricated on LaAlO3 (100) single crystal substrates with laser molecular beam epitaxy. The self-assembled growth was in-situ monitored by reflective high energy electron diffraction. The morphology evolutions of the films as a function of thickness were studied by ex-situ atomic force microscopy. As the thickness of the films increased from 3.875nm to 46.5nm gradually, the compressive stress-induced SrTiO3 films exhibited a periodic well-ordered ripple structure, which formed a unique nanoassembled template for the fabrication of quantum wires. Small angle X-ray scattering technique was employed to investigate the structure. Symmetric satellite peaks were discovered, indicating the well-ordered superstructure. In contrast, the similar superstructure was not observed during the growth of the tensile stress-induced LaAlO3 films on SrTiO3 substrates. The Compressive stress was considered as the main reason of the self-assembled growth, and systematical elucidation about strain mechanism was discussed. These results might provide an efficient method for the controllable formation of well-aligned template of quantum wire for complex oxide with desirable structure via proper modulation of strains.

scholarly journals Guided immobilisation of single gold nanoparticles by chemical electron beam lithography

2013 ◽  
Vol 4 ◽  
pp. 336-344 ◽  
Author(s):  
Patrick A Schaal ◽  
Ulrich Simon
Keyword(s):  
Gold Nanoparticles ◽  
Atomic Force Microscopy ◽  
Electron Beam ◽  
Self Assembly ◽  
Electron Beam Lithography ◽  
Current Interest ◽  
Force Microscopy ◽  
Periodic Arrays ◽  
Atomic Force ◽  
Step Procedure

The fabrication of periodic arrays of single metal nanoparticles is of great current interest. In this paper we present a straight-forward three-step procedure based on chemical electron beam lithography, which is capable of producing such arrays with gold nanoparticles (AuNPs). Preformed 6 nm AuNPs are immobilised on thiol patterns with a pitch of 100 nm by guided self-assembly. Afterwards, these arrays are characterised by using atomic force microscopy.

Dynamics of InAs Quantum Dots Formation on AlAs and GaAs

2000 ◽  
Vol 648 ◽  
Author(s):  
M. Yakimov ◽  
V. Tokranov ◽  
S. Oktyabrsky
Keyword(s):  
Quantum Dots ◽  
Self Assembly ◽  
Single Layer ◽  
High Energy ◽  
Ex Situ ◽  
Inas Quantum Dots ◽  
Force Microscopy ◽  
Atomic Force ◽  
Kinetics Of

AbstractWe have studied the formation of InAs quantum dots (QDs) grown by molecular beam epitaxy on top of GaAs and 2 ML-thick AlAs layers in the temperature range from 350 to 500°C. In-situ reflection high energy electron diffraction (RHEED) patterns were recorded in real time during the growth and analyzed to characterize the 2D-to-3D transition on the surface, including QD formation, and ripening process. The kinetics of QD formation was studied using the InAs growth rates ranging from 0.01 to 1 ML/s and different ratios of As2/In fluxes. RHEED patterns and ex-situ atomic force microscopy images were analyzed to reveal the development of sizes and shapes of the single-layer and stacked QD ensembles. The critical InAs coverage for QD formation was shown to be consistently higher for dots grown on the AlAs overlayer than for those grown on GaAs surface. Self-assembly of multilayer QD stacks revealed the reduction of the critical thickness for dots formed in the upper layers.

Clathrin-Inspired Coating and Stabilization of Liposomes by DNA Self-Assembly

2019 ◽  
Author(s):  
Kevin N. Baumann ◽  
Luca Piantanida ◽  
Javier García-Nafría ◽  
Diana Sobota ◽  
Kislon Voïtchovsky ◽  
...  
Keyword(s):  
Self Assembly ◽  
Mechanical Stability ◽  
Lipid Vesicles ◽  
The Self ◽  
Force Microscopy ◽  
Atomic Force ◽  
Cryo Electron Microscopy ◽  
Further Development ◽  
Liposome Surface ◽  
Dna Coating

The self-assembly of the protein clathrin on biological membranes facilitates essential processes of endocytosis in biological systems and has provided a source of inspiration for materials design by the highly ordered structural appearance. By mimicking the architecture of clathrin self-assemblies to coat liposomes with biomaterials, new classes of hybrid carriers can be derived. Here we present a method for fabricating DNA-coated liposomes by hydrophobically anchoring and subsequently growing a DNA network on the liposome surface which structurally mimics clathrin assemblies. Dynamic light scattering (DLS), ζ-potential and cryo-electron microscopy (cryo-EM) measurements independently demonstrate successful DNA coating. Nanomechanical measurements conducted with atomic force microscopy (AFM) show that the DNA coating enhances the mechanical stability of the liposomes relative to uncoated ones. Furthermore, we provide the possibility to reverse the coating process by triggering the disassembly of the DNA coating through a toehold-mediated displacement reaction. Our results describe a straightforward, versatile, and reversible approach for coating and stabilizing lipid vesicles by an interlaced DNA network. This method has potential for further development towards the ordered arrangement of tailored functionalities on the surfaces of liposomes and for applications as hybrid nanocarrier.

In situ X-ray Scattering Study of the Formation of Au Nano Crystals During Thermal Annealing

2007 ◽  
Vol 1027 ◽  
Author(s):  
Do Young Noh ◽  
Ki-Hyun Ryu ◽  
Hyon Chol Kang
Keyword(s):  
Thermal Annealing ◽  
Bragg Reflection ◽  
Ex Situ ◽  
X Ray ◽  
Force Microscopy ◽  
X Ray Scattering ◽  
Atomic Force ◽  
Au Thin Films ◽  
Ray Scattering

AbstractThe transformation of Au thin films grown on sapphire (0001) substrates into nano crystals during thermal annealing was investigated by in situ synchrotron x-ray scattering and ex situ atomic force microscopy (AFM). By monitoring the Au(111) Bragg reflection and the low Q reflectivity and comparing them with ex situ AFM images, we found that polygonal-shape holes were nucleated and grow initially. As the holes grow larger and contact each other, their boundary turns into Au nano crystals. The Au nano crystals have a well-defined (111) flat top surface and facets in the in-plane direction.

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