Precipitation of highly luminescent phases from PECVD Si suboxides

2004 ◽  
Vol 832 ◽  
Author(s):  
M. Perálvarez ◽  
M. López ◽  
B. Garrido ◽  
J.R. Morante ◽  
J. Barreto ◽  
...  
Keyword(s):  
Refractive Index ◽  
Phase Separation ◽  
Ion Implantation ◽  
Composition Profile ◽  
Matrix Composition ◽  
Light Sources ◽  
The Matrix ◽  
Detailed Composition ◽  
Preparation Route

ABSTRACTSi nanoclusters (Si-nc) embedded in SiO2 present outstanding luminescent emission in the visible and are the material of choice for the realization of efficient light sources integrated with Si technology. PECVD is an attractive preparation route but there is still the need to understand how Si excess and matrix composition affect the precipitation of Si-nc and their photoluminescence (PL) efficiency. The SiOx PECVD layers studied here have a Si excess up to 50% and a thickness between 50 and 100 nm. The phase separation, precipitation and growth of the Si-nc have been achieved by annealing at 1250 °C. For reference, the same study has been performed in Si-nc/SiO2 materials synthesized by ion implantation and annealing. Refractive index and thickness measured by ellipsometry show a densification of the layers after the H release during annealing. A detailed composition profile has been determined by XPS and FTIR analyses and shows almost complete phase separation except for the interfaces, where a depletion of Si-nc is found. EFTEM demonstrates that isolated Si-nc are formed for Si excess up to 25% while for higher Si excess a continuous Si phase is observed. The PL efficiency in PECVD samples is maximized for a Si excess of 17% which is the same Si excess than that for the most emitting implanted samples. No dependence of PL efficiency has been found on the presence of Nitrogen in the matrix (up to the 10%).

Interlayer mixing in GaAs/AlxGa1-xAs heterostructures as a result of Se+ ion implantation

1988 ◽  
Vol 46 ◽  
pp. 908-909
Author(s):  
E.G. Bithell ◽  
W.M. Stobbs
Keyword(s):  
Ion Implantation ◽  
Diffusion Coefficients ◽  
Dark Field ◽  
Atomic Mass ◽  
Composition Profile ◽  
Semiconductor Heterostructures ◽  
Transmission Electron ◽  
Microscope Images ◽  
Damage Process ◽  
Electron Energy Loss

It is well known that the microstructural consequences of the ion implantation of semiconductor heterostructures can be severe: amorphisation of the damaged region is possible, and layer intermixing can result both from the original damage process and from the enhancement of the diffusion coefficients for the constituents of the original composition profile. A very large number of variables are involved (the atomic mass of the target, the mass and energy of the implant species, the flux and the total dose, the substrate temperature etc.) so that experimental data are needed despite the existence of relatively well developed models for the implantation process. A major difficulty is that conventional techniques (e.g. electron energy loss spectroscopy) have inadequate resolution for the quantification of any changes in the composition profile of fine scale multilayers. However we have demonstrated that the measurement of 002 dark field intensities in transmission electron microscope images of GaAs / AlxGa1_xAs heterostructures can allow the measurement of the local Al / Ga ratio.

Inverse Ostwald Ripening and Self-Organization of Nanoclusters due to Ion Irradiation

2000 ◽  
Vol 647 ◽  
Author(s):  
K.-H. Heinig ◽  
B. Schmidt ◽  
M. Strobel ◽  
H. Bernas
Keyword(s):  
Phase Separation ◽  
Ion Implantation ◽  
Ostwald Ripening ◽  
Ion Irradiation ◽  
Experimental Studies ◽  
Self Organization ◽  
Mathematical Treatment ◽  
Thermodynamical Equilibrium ◽  
Unusual Behavior ◽  
Thermally Activated

AbstractUnder ion irradiation collisional mixing competes with phase separation if the irradiated solid consists of immiscible components. If a component is a chemical compound, there is another competition between the collisional forced chemical dissociation of the compound and its thermally activated re-formation. Especially at interfaces between immiscible components, irradiation processes far from thermodynamical equilibrium may lead to new phenomena. If the formation of nanoclusters (NCs) occurs during ion implantation, the phase separation caused by ion implantation induced supersaturation can be superimposed by phenomena caused by collisional mixing. In this contribution it will be studied how collisional mixing during high-fluence ion implantation affects NC synthesis and how ion irradiation through a layer of NCs modifies their size and size distribution. Inverse Ostwald ripening of NCs will be predicted theoretically and by kinetic lattice Monte-Carlo simulations. The mathematical treatment of the competition between irradiation-induced detachment of atoms from clusters and their thermally activated diffusion leads to a Gibbs-Thomson relation with modified parameters. The predictions have been confirmed by experimental studies of the evolution of Au NCs in SiO2 irradiated by MeV ions. The unusual behavior results from an effective negative capillary length, which will be shown to be the reason for inverse Ostwald ripening. Another new phenomenon to be addressed is self-organization of NCs in a d-layer parallel to the Si/SiO2 interface. Such d-layers were found when the damage level at the interface was of the order of 1-3 dpa. It will be discussed that the origin of the d-layer of NCs can be assigned to two different mechanisms: (i) The negative interface energy due to collisional mixing gives rise to the formation of tiny clusters of substrate material in front of the interface, which promotes heteronucleation of the implanted impurities. (ii) Collisional mixing in the SiO2produces diffusing oxygen, which may be consumed by the Si/SiO2 interface. A thin layer parallel to the interface becomes denuded of diffusing oxygen, which results in a strong pile up of Si excess. This Si excess promotes heteronucleation too. Independent of the dominating mechanism of self-organization of a d-layer of NCs, its location in SiO2 close to the SiO2/Si interface makes it interesting for non-volatile memory application.

scholarly journals The Polymerization of MMA and ST to Prepare Material with Gradient Refractive Index in Electric Field

2015 ◽  
Vol 2015 ◽  
pp. 1-6
Author(s):  
Yao Huang ◽  
Daming Wu ◽  
Dongyun Ren ◽  
Qingyun Meng ◽  
Xiaojun Di
Keyword(s):  
Molecular Weight ◽  
Refractive Index ◽  
Electric Field ◽  
Cylindrical Sample ◽  
Electrical Field ◽  
Molecular Weights ◽  
The Matrix ◽  
Gradient Refractive Index ◽  
Scattering Material ◽  
Different Parts

Light scattering material with gradient refractive index was prepared under the electrical field by taking methyl methacrylate (MMA) monomer as the matrix with the addition of a little preheated styrene (ST) and peroxidation benzoin formyl (BPO). The material obtained under electrical field presented different transmittance and molecular weight at different parts of the cylindrical sample along the axis of the direction of electric field which led to the layering phenomenon and gradient refractive index. The disparity of molecular weight between different layers can be as much as 230 thousand. There were several peaks in the figure of GPC test of the sample under electric field. This proved that there were polymers with different molecular weights in the sample. Therefore, it can be concluded that electrical field has a significant effect on polymerization.

SYNTHESIS OF ALLOY METAL NANOCLUSTERS IN SILICA GLASS BY SEQUENTIAL ION IMPLANTATION

2007 ◽  
Vol 06 (06) ◽  
pp. 423-430 ◽  
Author(s):  
B. JOSEPH ◽  
H. P. LENKA ◽  
P. K. KUIRI ◽  
D. P. MAHAPATRA ◽  
R. KESAVAMOORTHY
Keyword(s):  
Ion Implantation ◽  
Silica Glass ◽  
Metallic Nanoparticles ◽  
Rutherford Backscattering Spectrometry ◽  
Low Frequency ◽  
Peak Position ◽  
Negative Ion ◽  
Metal Nanoclusters ◽  
Cross Sectional ◽  
The Matrix

High fluence low energy negative ion implantation has been used to synthesize embedded metal nanoclusters of Au , Ag and Sb in silica glass. The Au - and Ag -implanted samples showed peaks, corresponding to surface plasmon resonance (SPR) in the optical absorption (OA) spectra, confirming the formation of metallic nanoparticles in the matrix. No SPR peak was observed in case of Sb -implanted samples which is attributed to the absence of pure metallic precipitates which could be detected in the OA spectrum. Low frequency Raman scattering (LFRS) measurements also confirm this. Cross-sectional transmission electron microscopy has been used to infer about the size distribution of the nanoparticles. Sequential implantations of Au and Ag or Au and Sb have been found to result in SPR peaks at locations in between those for nanoparticles of the constituent atoms, indicating the formation of alloy nanoparticles in the system. In case of the Au + Ag system, Rutherford backscattering spectrometry has been used to infer about the composition of the nanoparticles in terms of the concentrations of the metallic constituents. A direct, one-to-one correspondence between the SPR peak position and composition has been observed.

Slurry Wear Test of Long Kenaf Polyester Composite (LKPC) and Long Kenaf Polyester with Fiberglass Composite

2013 ◽  
Vol 393 ◽  
pp. 919-924
Author(s):  
Muhd Azimin Ab Ghani ◽  
A.F. Ahmad Kamal ◽  
Mohamad Ali Ahmad ◽  
Y.M.D. Taib ◽  
Z. Salleh ◽  
...  
Keyword(s):  
Sea Water ◽  
Wear Test ◽  
Matrix Composition ◽  
Slurry Erosion ◽  
Composite Surface ◽  
Wear And Friction ◽  
Fiberglass Composite ◽  
The Matrix ◽  
Polyester Composite ◽  
Erosion Test

This paper presents an experimental study on the influence of fiberglass woven in Long Kenaf Polyester Composite (LKPC). Wear and friction characteristics were examined using sea water and sand as a slurry. Wear test were carried out using Slurry Erosion Test Rig (TR-40). These tests were performed at room temperature with speed of 200 rpm for every 2 km interval. The results from the tests show that mass loss were depends on the matrix composition of the composite. Surface Roughness, Ra, was consistently reduced after each test in all cases.

Influence of WC Particle Size and Matrix Composition on the Behavior of WC-Co-Cr Coatings Sprayed by the HVOF Process

1997 ◽  
Author(s):  
J. Berget ◽  
E. Bardal ◽  
T. Rogne
Keyword(s):  
Particle Size ◽  
Wear Resistance ◽  
Corrosion Resistance ◽  
Chromium Content ◽  
Deposition Efficiency ◽  
Matrix Composition ◽  
Coating Properties ◽  
Hvof Process ◽  
Erosion Corrosion ◽  
The Matrix

Abstract WC-Co-Cr powders with different WC particle size have been sprayed by the HVOF process. At constant spraying conditions the powders give coatings of different quality. The deposition efficiency during spraying of powders containing large WC particles was found to be low compared to powders with finer WC grains. In addition the amounts of porosity and cracks were different. The coatings have been characterised by different methods. Erosion and erosion-corrosion tests showed that the WC particle size also influence the wear resistance of the coatings. Small WC particle size was found to be beneficial. Chemical composition of the matrix was also found to be decisive for the coating properties. An increase of the chromium content improved the erosion-corrosion resistance.

New Transparent Substrate with Silica Aerogel Film for Surface-Emissive Devices

2000 ◽  
Vol 660 ◽  
Author(s):  
H. Yokogawa ◽  
K. Kawano ◽  
M. Yokoyama ◽  
T. Tsutsui ◽  
M. Yahiro ◽  
...  
Keyword(s):  
Refractive Index ◽  
Glass Substrate ◽  
Silica Aerogel ◽  
Sol Gel ◽  
Supercritical Drying ◽  
Transparent Electrode ◽  
Light Sources ◽  
Photoluminescence Intensity ◽  
Transparent Substrate ◽  
Low Refractive Index

ABSTRACTSilica aerogels prepared by sol-gel methods with supercritical drying process have transparency and extremely low refractive index which is not available in any other materials. This extraordinary refractivity is expected to present some new features as an optical material. Ordinarily, coupling-out efficiency of surface-emissive light sources has been assumed to be low. It is due to the losses organized from internal reflection of emitted light at the air-glass interface and dissipation during wave-guiding propagation within the substrate.However, when material that has extremely low refractive index is inserted between a thin luminescence layer and glass substrate, almost all the light from the luminescence layer can efficiently couple out to air passing through the glass substrate. In this report, we introduce a silica aerogel film as a low refractive index material for surface-emissive devices, such as photoluminescent and electroluminescent device. In the experiments, the photoluminescence intensity of Alq3 through the silica aerogel layer was twice as large as that of the glass substrate without the silica aerogel film. Moreover, we formed a new substrate which contained a transparent electrode on the silica aerogel film. Using this substrate, we fabricated the OLED and observed the disappearance of wave-guiding propagation within the glass substrate.

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