Luminescent Colloidal SI Suspensions from Porous SI

1991 ◽  
Vol 256 ◽  
Author(s):  
Julie L. Heinrich ◽  
Corrine L. Curtis ◽  
Grace M. Credo ◽  
Karen L. Kavanagh ◽  
Michael J. Sailor
Keyword(s):  
Quantum Confinement ◽  
Methylene Chloride ◽  
Colloidal Suspensions ◽  
Porous Si ◽  
Irregular Shapes ◽  
Quantum Confinement Effects ◽  
Transmission Electron ◽  
Si Nanoparticles ◽  
Si Films ◽  
P Type

ABSTRACTA procedure for generating colloidal suspensions of Si exhibiting luminescence, attributed to quantum confinement effects, is described. Samples of n- or p-type Si, that have been electrochemically etched to form porous Si, can be ultrasonically dispersed into methylene chloride, acetonitrile, methanol, toluene, or water solvents, forming a suspension of fine Si particles that luminesce. Transmission electron microscopy analyses show the Si particles to have irregular shapes, with diameters ranging from many microns to nanometers. Luminescent, composite polystyrene/Si films can be made by the addition of polystyrene to a toluene suspension of the Si nanoparticles and casting of the resulting solution.

Optical properties of porous silicon

1992 ◽  
Vol 70 (10-11) ◽  
pp. 1184-1193 ◽  
Author(s):  
D. J. Lockwood ◽  
G. C. Aers ◽  
L. B. Allard ◽  
B. Bryskiewicz ◽  
S. Charbonneau ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Confinement ◽  
Chemical Dissolution ◽  
Optical Absorption Spectra ◽  
Porous Si ◽  
Transmission Electron ◽  
Amorphous Si ◽  
Si Nanostructures ◽  
Si Films

The optical and structural properties of porous Si films produced by electrochemical and chemical dissolution of Si have been studied by a variety of techniques. Raman scattering and transmission electron microscopy have shown the samples to contain crystalline Si wires and (or) spherites 3–8 nm in diameter and (or) amorphous Si. The optical absorption spectra and the wavelength, temperature, and lifetime dependence of the photoluminescence obtained from most of the samples are entirely consistent with the quantum confinement of excitons in Si nanostructures. Quite different photoluminescence was obtained from other samples composed only of amorphous Si, and this is attributed to the presence of silicon oxyhydride species.

Development of Silicon-Based UV-Photodetector Prototypes using Photoluminescent Nanocrystalline Silicon Overlayers

2000 ◽  
Vol 638 ◽  
Author(s):  
Carlos Navarro ◽  
Luis F. Fonseca ◽  
Guillermo Nery ◽  
O. Resto ◽  
S. Z. Weisz
Keyword(s):  
Porous Silicon ◽  
Active Zone ◽  
Silicon Detector ◽  
Nanocrystalline Silicon ◽  
Incident Radiation ◽  
Enhancement Effect ◽  
Type Silicon ◽  
Quantum Confinement Effects ◽  
Si Films ◽  
P Type

AbstractThe maximum photoresponse of a normal silicon photodetector, that uses a p-n junction as the active zone, is obtained when the incident radiation wavelength is around 750nm. This response diminishes significantly when the incident radiation is near or in the UV region. Meanwhile, nanocrystalline silicon (nc-Si) films with high transparency above 650nm and high absorbance in the UV can be prepared. By quantum confinement effects, a fraction of this absorbed UV energy is re-emitted as visible photons that can be used by the junction. We study the enhancement of the UV-photoresponse of two silicon detector prototypes with a silicon p-n junction active zone and with a photoluminescent nc-Si overlayer. One prototype is made with a porous silicon/n-type silicon/p-type silicon/p++-silicon/metal configuration and the other with an Eu-doped Si-SiO2 overlayer instead of the porous silicon one. The comparison between both prototypes and the control is presented and discussed stressing on the enhancement effect introduced by the photoluminescent overlayers, stability and reproducibility.

Synthesis and Compositional Control of Size Monodisperse SixGe1-x Nanocrystals for Optoelectronic Applications

2013 ◽  
Vol 1551 ◽  
pp. 11-16
Author(s):  
Keith Linehan ◽  
Darragh Carolan ◽  
Daithi Ó Sé ◽  
Hugh Doyle
Keyword(s):  
Silicon Germanium ◽  
Quantum Confinement ◽  
Room Temperature ◽  
Blue Emission ◽  
Excitation Wavelength ◽  
Microscopy Imaging ◽  
Quantum Confinement Effects ◽  
Transmission Electron ◽  
Co Reduction ◽  
Compositional Control

ABSTRACTAlkyl-terminated SixG1-x nanocrystals are prepared at room temperature by co-reduction of Si and Ge precursors by hydride reducing agents within inverse micelles. Compositional control of the alloy silicon-germanium NCs (ca. 3.6 nm) is achieved by varying the relative amounts of each precursor used in the synthesis. Transmission electron microscopy imaging confirmed that the NCs are highly crystalline with a narrow size distribution; optical spectroscopy shows strong quantum confinement effects, with moderate absorption in the UV spectral range, and a strong blue emission with a marked dependency on excitation wavelength.

Electron Microscopy of Mesoscale Arrays of Quantum-Confined CdS Nanoparticles Formed on DNA Templates

1996 ◽  
Vol 452 ◽  
Author(s):  
Russell F. Pinizzotto ◽  
Young G. Rho ◽  
Yandong Chen ◽  
Robert M. Pirtle ◽  
Irma L. Pirtle ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Quantum Confinement ◽  
Cds Nanoparticles ◽  
Dna Templates ◽  
Quantum Confinement Effects ◽  
Transmission Electron ◽  
Quantum Confined ◽  
Processing Techniques ◽  
State Processing

AbstractThis paper describes the fabrication method and initial characterization of self-assembled mesoscale arrays of quantum-confined CdS nanoparticles using DNA as a template for the overall shape. Three DNAs were used: the circular and linear forms of the plasmid pUCLeu4, and circular φ×174 RF II. In all three cases, the mesoscale lengths are consistent with the A-form of DNA. The structural signatures and crystallography were confirmed using conventional and high resolution transmission electron microscopy, and electron diffraction. Optical spectroscopy demonstrated that the particles display quantum-confinement effects. This research is a fundamental demonstration of the power of combining biochemical and solid-state processing techniques.

Nanostructure of Porous Silicon Using Transmission Microscopy

1998 ◽  
Vol 536 ◽  
Author(s):  
M. H. Nayfeh ◽  
Z. Yamani ◽  
O. Gurdal ◽  
A. Alaql
Keyword(s):  
Electron Microscopy ◽  
Diffuse Scattering ◽  
Amorphous State ◽  
Coherent Scattering ◽  
Porous Si ◽  
Island Size ◽  
Transmission Microscopy ◽  
Transmission Electron ◽  
Uppermost Layer ◽  
P Type

AbstractWe use high resolution transmission electron microscopy (XTEM) to image the nanostructure of (100) p-type porous Si. A network of pore tracks subdivide the material into nanoislands and nanocrystallites are resolved through out the material. With distance from the substrate, electron diffraction develops, in addition to coherent diffraction, amorphous-like patterns that dominates the coherent scattering in the topmost luminescent layer. Also, with distance from the substrate, crystalline island size diminshes to as small as 1 nm in the topmost luminescence material. Although their uppermost layer has the most resolved nano crystallites, it has the strongest diffuse scattering of all regions. This suggests that the diffuse scattering is due to a size reduction effects rather than to an amorphous state. We discuss the relevance of a new dimer restructuring model in ultra small nanocrystallites to the loss of crystalline effects.

Porous Amorphous Si Formation by the Etching of Single Crystal Si Substrates

1992 ◽  
Vol 259 ◽  
Author(s):  
T. George ◽  
R. P. Vasquez ◽  
S. S. Kim ◽  
R.W. Fathauer ◽  
W. T. Pike
Keyword(s):  
Photoelectron Spectroscopy ◽  
Light Emitting ◽  
X Ray ◽  
Si Substrates ◽  
Transmission Electron ◽  
Spin Resonance ◽  
Amorphous Si ◽  
Si Films ◽  
P Type ◽  
Stain Etching

ABSTRACTThe nature of light-emitting porous Si layers produced by non-anodic stain etching of p-type (100) Si substrates is studied. The layers were characterized by transmission electron microscopy as being amorphous in nature. X-ray photoelectron spectroscopy and electron spin resonance measurements show these layers to be composed mainly of a-Si. The formation mechanism of the a-Si is explored using by stain etching SiGe ‘marker’ layers within epitaxially grown Si films and by high temperature annealing. These experiments provide strong evidence for a spontaneous crystalline-amorphous phase transformation during the etching process.

Evaluation of Optical Properties for Nanocrystal Si Dot Layers Fabricated by CVD as a Function of Size Reduction

2012 ◽  
Vol 725 ◽  
pp. 251-254
Author(s):  
Yuki Mizukami ◽  
D. Kosemura ◽  
M. Takei ◽  
Y. Numasawa ◽  
Y. Ohshita ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Optical Properties ◽  
Quantum Confinement ◽  
Vapour Deposition ◽  
Chemical Vapour ◽  
X Ray Diffraction ◽  
Confinement Effects ◽  
Quantum Confinement Effects ◽  
Transmission Electron

Raman spectroscopy and photoluminescence were performed in order to understand the optical properties of nanocrystal Si in relation to quantum confinement effects. The nanocrystal Si (nc-Si) dots in the SiO2 layer were fabricated by the H2 plasma treatment and chemical vapour deposition followed by the oxidation of the nc-Si dots surface. The post-annealing was also performed to improve the crystalline quality of nc-Si at 1050 °C for 5 and 10 min. There is a good correlation of the quantum confinement effects between the results of Raman spectroscopy and photoluminescence. The Raman spectra from nc-Si were analysed using the model of Richter et al. As a result, the sizes of the nc-Si dots were consistent with those obtained by transmission electron microscopy and X-ray diffraction. Moreover, the compressive stress in the nc-Si dots were evaluated which was induced by the SiO2 surroundings.

Synthesis and Characterization of CdS Nanoparticles

2013 ◽  
Vol 848 ◽  
pp. 3-6
Author(s):  
Xiao Hui Fan ◽  
Hong Juan Liu ◽  
Yan Ming Chen ◽  
Ting Sun
Keyword(s):  
Electron Microscopy ◽  
Quantum Confinement ◽  
Cadmium Acetate ◽  
Synthesis And Characterization ◽  
Cds Nanoparticles ◽  
Narrow Size Distribution ◽  
Quantum Confinement Effects ◽  
Transmission Electron ◽  
Tem Transmission Electron Microscopy

CdS nanoparticles were synthesized by using PVP (polyvinylpyrrolidone) as macromolecular surfactant, N, N-dimethylformamide as solvent, cadmium acetate and thiourea as precursors. The optical properties and morphologies for the synthesized CdS nanoparticles were characterized by UV-Vis absorption spectroscopy and TEM (transmission electron microscopy) measurements. The results show that PVP could act as a better stabilizer for the formation of CdS nanoparticles in N, N-dimethylformamide. The obtained CdS nanoparticles have spherical morphology and a narrow size distribution. CdS nanoparticles could give an apparent extionic absorption peaks and quantum confinement effects.

Synthesis and Characterization of ZnS Nanoparticles by Using Polyvinylpyrrolidone as Stabilizer

2012 ◽  
Vol 625 ◽  
pp. 269-272
Author(s):  
Xiao Hui Fan ◽  
Hong Juan Liu ◽  
Yan Ming Chen ◽  
Ting Sun
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Confinement ◽  
Synthesis Method ◽  
Synthesis And Characterization ◽  
Narrow Size Distribution ◽  
Zns Nanoparticles ◽  
Quantum Confinement Effects ◽  
Transmission Electron

A simple synthesis method of PVP (polyvinylpyrrolidone) coated ZnS QDS has been developed. The optical properties and morphology for the as-synthesized ZnS nanoparticles were characterized by UV-Vis absorption spectroscopies and transmission electron microscopy (TEM). The results show that PVP could act as a better stabilizer for the formation of ZnS nanoparticles in N, N-dimethylformamide. The obtained ZnS nanoparticles have spherical morphology and a narrow size distribution. ZnS nanoparticles could give an apparent extionic absorption peaks and quantum confinement effects.

Understanding the structure of Si nanoclusters in a/nc-Si:H films using spherical aberration-corrected transmission electron microscopy

2004 ◽  
Vol 808 ◽  
Author(s):  
Christopher R. Perrey ◽  
Siri S. Thompson ◽  
Markus Lentzen ◽  
Uwe Kortshagen ◽  
C. Barry Carter
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Spherical Aberration ◽  
Objective Lens ◽  
Transmission Electron ◽  
Si Nanoparticles ◽  
Twin Defects ◽  
Si Films ◽  
Hydrogenated Amorphous ◽  
Aberration Corrected

ABSTRACTRecent work has shown that the electrical properties of hydrogenated amorphous Si films with nanocrystalline inclusions (a/nc-Si:H) make this material a promising candidate for applications in solar cells. The present study applies the technique of spherical aberration-corrected high-resolution transmission electron microscopy for the identification and analysis of the crystalline content of an a/nc-Si:H film. By varying both the spherical aberration of the objective lens and the defocus, regions of crystallinity in the a/nc-Si:H film can be identified. This study reports the analysis of Si nanoparticles of approximately 1.5 nm in size. Some of these nanoparticles contain planar defects, such as twin defects and stacking faults. All particles observed were the same crystal structure as bulk Si, which agrees with theoretical cluster calculations. Beam damage was observed in the amorphous matrix for long electron–beam exposures.

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