Assembly of CdSe/CdS Quantum Dots on Au Surfaces for Photoreception

2003 ◽  
Vol 796 ◽  
Author(s):  
Jing Tang ◽  
Henrik Birkedal ◽  
Eric W. McFarland ◽  
Galen D. Stucky
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Schottky Barrier ◽  
Photoelectron Spectroscopy ◽  
Deposition Process ◽  
High Coverage ◽  
Covalent Bonds ◽  
Force Microscopy ◽  
Atomic Force ◽  
Barrier Device

ABSTRACTCdSe/CdS core/shell quantum dots have been synthesized and assembled onto pre-functionalized gold surfaces by either hydrogen bonding or covalent bonds through different functional groups. Control of the conditions during the deposition process allows producing a high coverage of quantum dots via molecular linkages. The quantum-dot surface is highly photoactive and is used in a surface sensitized Schottky barrier photovoltaic structure as the photoreception component. Atomic force microscopy (AFM) and X-ray photoelectron Spectroscopy (XPS) are used to characterize and confirm the morphology and linkage of the assemblies on Au surfaces. The electron transfer from the quantum-dot layer to the Schottky barrier device is examined by measuring the current-voltage (IV) curve of such photovoltaic devices under simulated sun light.

scholarly journals Superhydrophilic Coating with Antibacterial and Oil-Repellent Properties via NaIO4-Triggered Polydopamine/Sulfobetaine Methacrylate Polymerization

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2008
Author(s):  
Hsiu-Wen Chien ◽  
Hong-Yu Lin ◽  
Chau-Yi Tsai ◽  
Tai-Yu Chen ◽  
Wei-Nian Chen
Keyword(s):  
Surface Modification ◽  
Photoelectron Spectroscopy ◽  
Deposition Process ◽  
Water Contact ◽  
Water Separation ◽  
Force Microscopy ◽  
Atomic Force ◽  
Oil Water Separation ◽  
One Step ◽  
Oil Repellent

Superhydrophilic coatings have been widely used for the surface modification of membranes or biomedical devices owing to their excellent antifouling properties. However, simplifying the modification processes of such materials remains challenging. In this study, we developed a simple and rapid one-step co-deposition process using an oxidant trigger to fabricate superhydrophilic surfaces based on dopamine chemistry with sulfobetaine methacrylate (SBMA). We studied the effect of different oxidants and SBMA concentrations on surface modification in detail using UV–VIS spectrophotometry, dynamic light scattering, atomic force microscopy, X-ray photoelectron spectroscopy, and surface plasmon resonance. We found that NaIO4 could trigger the rate of polymerization and the optimum ratio of dopamine to SBMA is 1:25 by weight. This makes the surface superhydrophilic (water contact angle < 10°) and antifouling. The superhydrophilic coating, when introduced to polyester membranes, showed great potential for oil/water separation. Our study provides a complete description of the simple and fast preparation of superhydrophilic coatings for surface modification based on mussel-inspired chemistry.

Influence of quantum dots shape approximation on size reconstructed from atomic force microscopy measurements

2009 ◽  
Vol 17 (3) ◽  
Author(s):  
T. Piotrowski ◽  
S. Sikorski
Keyword(s):  
Quantum Dots ◽  
Atomic Force Microscopy ◽  
Quantum Dot ◽  
Size Determination ◽  
Force Microscopy ◽  
Atomic Force ◽  
Growth Plane ◽  
Shape Approximation ◽  
Afm Probe

AbstractIn this work we discuss the influence of the atomic force microscopy (AFM) probe tip geometry and the object — quantum dot form on the quantum dots dimension in the growth plane reconstructed from the AFM measurements. It is shown that ignoring the geometry of the probe tip and the quantum dot leads to significant differences between dimensions obtained from the AFM measurements and the real dimensions. Inaccuracies in QD size determination of the nano-objects from AFM measurements are defined.

InP Self Assembled Quantum Dot Lasers Grown on GaAs Substrates by Metalorganic Chemical Vapor Deposition

2001 ◽  
Vol 692 ◽  
Author(s):  
R. D. Dupuis ◽  
J. H. Ryou ◽  
R. D. Heller ◽  
G. Walter ◽  
D. A. Kellogg ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Chemical Vapor ◽  
Active Regions ◽  
Threshold Current ◽  
Double Quantum ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Inp Quantum Dots

AbstractWe describe the operation of lasers having active regions composed of InP selfassembled quantum dots embedded in In0.5Al0.3Ga0.2P grown on GaAs (100) substrates by MOCVD. InP quantum dots grown on In0.5Al0.3Ga0.2P have a high density on the order of about 1–2×10 cm−2 with a dominant size of about 10–15 nm for 7.5 ML growth.[1] These In0.5Al0.3Ga0.2P/InP quantum dots have previously been characterized by atomic-force microscopy, high-resolution transmission electron microscopy, and photoluminescence.[2] We report here the 300K operation of optically pumped red-emitting quantum dots using both double quantum-dot active regions and quantum-dot coupled with InGaP quantum-well active regions. Optically and electrically pumped 300K lasers have been obtained using this active region design; these lasers show improved operation compared to the lasers having QD-based active regions with threshold current densities as low as Jth ∼ 0.5 KA/cm2.

Atomic Force Microscopy and Near-Field Scanning Optical Microscopy Study of Quantum-Dot Assemblies and Fractal Films

1999 ◽  
Vol 5 (S2) ◽  
pp. 968-969
Author(s):  
W. D. Bragg ◽  
K. Banerjee ◽  
M. J. Campin ◽  
Z. C. Ying ◽  
Jane G. Zhu ◽  
...  
Keyword(s):  
Thin Films ◽  
Quantum Dots ◽  
Atomic Force Microscopy ◽  
Quantum Dot ◽  
Optical Microscopy ◽  
Metal Salt ◽  
Fractal Structures ◽  
Force Microscopy ◽  
Atomic Force ◽  
Scanning Optical Microscopy

Quantum dots and nanocrystalline films are interesting materials due to their novel properties, not achievable from the bulk materials [1]. New materials fabricated by assembling of quantum dots and nanostructured materials exhibit, for example, high optical nonlinearities. Fractal structures [2] can be formed from quantum-dot aggregates or films. Scanning probe microscopy is the essential technique to characterize these nanometer-scaled materials?Gold nanocluster colloids are synthesized in the interior of surfactant aggregates known as inverse micelles, without the use of water to solubilize the metal salt [3]. The size of the Au quantum dots is well controlled in the colloid synthesis and selected using chromatography. The Au clusters are then sprayed onto a glass slides to form thin films made of Au quantum dots. We have also used the laser ablation technique [4] to grow Ag nanoparticles, fractal aggregates and thin films. These samples have been studied using atomic force microscopy (AFM) and nearfield scanning optical microscopy.

Dual Quantum Dot Superlattice

2018 ◽  
Vol 27 (01n02) ◽  
pp. 1840003
Author(s):  
Barath Parthasarathy ◽  
Pial Mirdha ◽  
Jun Kondo ◽  
Faquir Jain
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Field Effect Transistor ◽  
Crystalline Silicon ◽  
Force Microscopy ◽  
Atomic Force ◽  
Effect Transistor ◽  
P Type ◽  
Dual Quantum

In this paper, we propose a structure using four layers of quantum dots on crystalline silicon. The quantum dots site-specifically self-assembled in the p-type material due to the electrostatic attraction. This quantum dot super lattice (QDSL) structure will be constructed using a mixed layer of Germanium (Ge) and Silicon (Si) dots. Atomic Force Microscopy results will show the accurate stack height formed from individual and multi stacked layers. This is the first novel characterization of 4 layers of 2 separate self assemblies. This was also applied to a quantum dot gate field effect transistor (QDG-FET).

scholarly journals Kelvin probe force microscopy of the nanoscale electrical surface potential barrier of metal/semiconductor interfaces in ambient atmosphere

2019 ◽  
Vol 10 ◽  
pp. 1401-1411
Author(s):  
Petr Knotek ◽  
Tomáš Plecháček ◽  
Jan Smolík ◽  
Petr Kutálek ◽  
Filip Dvořák ◽  
...  
Keyword(s):  
Schottky Barrier ◽  
Photoelectron Spectroscopy ◽  
Deep Oxidation ◽  
Kelvin Probe Force Microscopy ◽  
Ambient Atmosphere ◽  
Kelvin Probe ◽  
Force Microscopy ◽  
Semiconductor Interfaces ◽  
Atomic Force ◽  
Long Time

This study deals with the preparation and characterization of metallic nanoinclusions on the surface of semiconducting Bi2Se3 that could be used for an enhancement of the efficiency of thermoelectric materials. We used Au forming a 1D alloy through diffusion (point nanoinclusion) and Mo forming thermodynamically stable layered MoSe2 nanosheets through the reaction with the Bi2Se3. The Schottky barrier formed by the 1D and 2D nanoinclusions was characterized by means of atomic force microscopy (AFM). We used Kelvin probe force microscopy (KPFM) in ambient atmosphere at the nanoscale and compared the results to those of ultraviolet photoelectron spectroscopy (UPS) in UHV at the macroscale. The existence of the Schottky barrier was demonstrated at +120 meV for the Mo layer and −80 meV for the Au layer reflecting the formation of MoSe2 and Au/Bi2Se3 alloy, respectively. The results of both methods (KPFM and UPS) were in good agreement. We revealed that long-time exposure (tens of seconds) to the electrical field leads to deep oxidation and the formation of perturbations greater than 1 µm in height, which hinder the I–V measurements.

scholarly journals Fast and Straightforward Synthesis of Luminescent Titanium(IV) Dioxide Quantum Dots

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Václav Štengl ◽  
Jiří Henych ◽  
Martin Šťastný ◽  
Martin Kormunda
Keyword(s):  
Quantum Dots ◽  
Photoelectron Spectroscopy ◽  
High Resolution Electron Microscopy ◽  
Fast Method ◽  
X Ray ◽  
Force Microscopy ◽  
Selected Area Electron Diffraction ◽  
Atomic Force ◽  
Resolution Electron ◽  
Close Range

The nucleus of titania was prepared by reaction of solution titanium oxosulphate with hydrazine hydrate. These titania nuclei were used for titania quantum dots synthesis by a simple and fast method. The prepared titanium(IV) dioxide quantum dots were characterized by measurement of X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), high-resolution electron microscopy (HRTEM), and selected area electron diffraction (SAED). The optical properties were determined by photoluminescence (PL) spectra. The prepared titanium(IV) dioxide quantum dots have the narrow range of UV excitation (365–400 nm) and also a close range of emission maxima (450–500 nm).

Synthesis and Characterization of Electrostatical Self-Assembly CdSe/Polymer Nanocomposite Films

2002 ◽  
Vol 733 ◽  
Author(s):  
Liangmin Zhang ◽  
Fajian Zhang ◽  
R. O. Claus
Keyword(s):  
Quantum Dots ◽  
Photoelectron Spectroscopy ◽  
Self Assembly ◽  
Polymer Nanocomposite ◽  
Nanocomposite Films ◽  
Cdse Quantum Dots ◽  
Layer By Layer ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron

AbstractUsing a novel electrostatic self-assembly (ESA) method to incorporate CdSe quantum dots into polymer we have successfully synthesized ultrathin films. This method allows the molecular-level thickness control and layer-by-layer formation of multilayer thin and thick films using alternative anionic and cationic molecular solution dipping. From ellipsometric measurements, we obtained that the thickness of per bilayer is around 3.7 nm. UV-vis absorption spectra versus the number of bilayers have also been obtained using an Hitachi 2001 spectrometer. The size of CdSe quantum dots has been measured using transmission electron microscopy before the CdSe quantum dots are incorporated and confirmed using atomic force microscopy after the formation of the film, respectively. Both measurements indicate that the diameter of the CdSe quantum dots is 2-3 nm. Xray photoelectron spectroscopy indicates that the concentration of the CdSe quantum dots in the film is 2.14%.

Investigation of the Effect of Uv-Assisted Oxidation and Nitridation of Hafnium Metal Films

2003 ◽  
Vol 780 ◽  
Author(s):  
C. Essary ◽  
V. Craciun ◽  
J. M. Howard ◽  
R. K. Singh
Keyword(s):  
Uv Radiation ◽  
Photoelectron Spectroscopy ◽  
Grazing Angle ◽  
X Ray Diffraction ◽  
Metal Thin Films ◽  
X Ray ◽  
Force Microscopy ◽  
Si Substrates ◽  
Atomic Force ◽  
Silicon Interface

AbstractHf metal thin films were deposited on Si substrates using a pulsed laser deposition technique in vacuum and in ammonia ambients. The films were then oxidized at 400 °C in 300 Torr of O2. Half the samples were oxidized in the presence of ultraviolet (UV) radiation from a Hg lamp array. X-ray photoelectron spectroscopy, atomic force microscopy, and grazing angle X-ray diffraction were used to compare the crystallinity, roughness, and composition of the films. It has been found that UV radiation causes roughening of the films and also promotes crystallization at lower temperatures.Furthermore, increased silicon oxidation at the interface was noted with the UVirradiated samples and was shown to be in the form of a mixed layer using angle-resolved X-ray photoelectron spectroscopy. Incorporation of nitrogen into the film reduces the oxidation of the silicon interface.

scholarly journals Photocatalytic reduction of graphene oxide with cuprous oxide film under UV-vis irradiation

2020 ◽  
Vol 59 (1) ◽  
pp. 207-214 ◽  
Author(s):  
Yao Wang ◽  
Jianqing Feng ◽  
Lihua Jin ◽  
Chengshan Li
Keyword(s):  
Graphene Oxide ◽  
Photoelectron Spectroscopy ◽  
Low Cost ◽  
Photocatalytic Reduction ◽  
Force Microscopy ◽  
Atomic Force ◽  
Reduced Graphene ◽  
Reduction Efficiency ◽  
Metal Organic ◽  
Reduction Effect

AbstractWe have grown Cu2O films by different routes including self-oxidation and metal-organic deposition (MOD). The reduction efficiency of Cu2O films on graphene oxide (GO) synthesized by modified Hummer’s method has been studied. Surface morphology and chemical state of as-prepared Cu2O film and GO sheets reduced at different conditions have also been investigated using atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS). Results show that self-oxidation Cu2O film is more effective on phtocatalytic reduction of GO than MOD-Cu2O film. Moreover, reduction effect of self-oxidation Cu2O film to GO is comparable to that of environmental-friendly reducing agent of vitamin C. The present results offer a potentially eco-friendly and low-cost approach for the manufacture of reduced graphene oxide (RGO) by photocatalytic reduction.

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