Search results for "silicon"
showing 10 items of 1391 documents
Peculiarities of photoluminescence excited by 157nm wavelength F2 excimer laser in fused and unfused silicon dioxide
2009
Abstract Photoluminescence (PL) spectra and kinetics of high purity amorphous silicon dioxide with ultra low hydroxyl content is studied under the excitation by F 2 excimer laser (157 nm wavelength) pulses. Materials synthesized in the SPCVD plasma chemical process are studied before and after fusion. Two bands are found in the PL spectra: one centered at 2.6–2.9 eV (a blue band) and the other at 4.4 eV (a UV band). Luminescence intensity of unfused material is found to increase significantly with exposure time starting from a very small level, whereas in fused counterpart it does not depend on irradiation time. Both bands show complicated decay kinetics, to which add exponential and hyperb…
On the Origin of Light Emission in Silicon Rich Oxide Obtained by Low-Pressure Chemical Vapor Deposition
2012
Silicon Rich Oxide (SRO) has been considered as a material to overcome the drawbacks of silicon to achieve optical functions. Various techniques can be used to produce it, including Low-Pressure Chemical Vapor Deposition (LPCVD). In this paper, a brief description of the studies carried out and discussions of the results obtained on electro-, cathode-, and photoluminescence properties of SRO prepared by LPCVD and annealed at 1,100°Care presented. The experimental results lead us to accept that SRO emission properties are due to oxidation state nanoagglomerates rather than to nanocrystals. The emission mechanism is similar to Donor-Acceptor decay in semiconductors, and a wide emission spectr…
Photoluminescence from silicon nanocrystals initiated by Auger recombination
2006
Abstract The mechanism of intense photoluminescence (PL) of silicon nanocrystals (nc-si), so interpreted as recombinative emission is reconsidered. Analysis of available theoretical and experimental data is presented to show that nc-si have an indirect band structure and, therefore, it is doubtful that electron–hole recombination is the only mechanism of intense emission. A model is proposed according to which a fraction of electrons reaches the second conduction sub-band by Auger recombination, a part of intense visible radiation being caused by direct electron transitions from the second conduction sub-band to the first one. Continuity equations are constructed in the first and the second…
Luminescent properties of GaN films grown on porous silicon substrate
2010
Abstract GaN films have been grown on porous silicon at high temperatures (800–1050 °C) by metal organic vapor phase epitaxy. The optical properties of GaN layers were investigated by photoluminescence (PL) and cathodoluminescence (CL) spectroscopy. PL spectra recorded at 5 K exhibit excitonic emissions around 3.36–3.501 eV and a broad yellow luminescence at 2.2 eV. CL analysis at different electron excitation conditions shows spatial non-uniformity in-depth of the yellow and the band-edge emissions. These bands of luminescence are broadened and red- or blue-shifted as the electron beam penetrates in the sample. These behaviors are explained by a change of the fundamental band gap due to re…
The evolution of the fraction of Er ions sensitized by Si nanostructures in silicon-rich silicon oxide thin films
2009
Photoluminescence (PL) and time-resolved PL experiments as a function of the elaboration process are performed on Er-doped silicon-rich silicon oxide (SRO:Er) thin films grown under NH(3) atmosphere. These PL measurements of the Er(3+) emission at 1.54 microm under non-resonant pumping with the Er f-f transitions are obtained for different Er(3+) concentrations, ranging from 0.05 to 1.4 at.%, and various post-growth annealing temperatures of the layers. High resolution transmission electron microscopy (HRTEM) and energy-filtered TEM (EFTEM) analysis show a high density of Si nanostructures composed of amorphous and crystalline nanoclusters varying from 2.7 x 10(18) to 10(18) cm(-3) as a fun…
Sub-band-gap-excited luminescence of localized states in SiO2–Si and SiO2–Al glasses
2010
Abstract Silica glass samples doped with extra silicon (SiO 2 –Si: artificial oxygen deficiency) and with aluminum (SiO 2 –Al: Al-doped without accompanying alkali ions) were studied. The luminescence properties of these two samples are compared in the range of temperature 15–290 K under excitation of ArF excimer laser (193 nm). In both samples the luminescence of oxygen deficient centers (ODCs) is detected, i.e., emission bands in the blue at 440 nm and the UV at 280 nm. Cooling of the both samples led to strong increases of luminescence intensity down to 80 K with much smaller increases for still lower temperatures. At 290 K in SiO 2 –Si a luminescence similar to that of twofold-coordinat…
Impact of fluorine admixture, hydrogen loading, and exposure to ArF excimer laser on photoluminescence of bismuth defects in amorphous silica
2013
Abstract Photoluminescence (PL) excited by ArF (193 nm), KrF (248 nm) and N 2 (337 nm) pulsed lasers is studied in bismuth doped unfused silicon dioxide synthesized on silica substrates by surface-plasma chemical vapor deposition (SPCVD). Additive free and fluorinated (F content ~ 0.4 wt.%) amorphous silica are examined as host materials for bismuth. Three typical PL bands peaking at wavelengths of 650 nm (orange), 800 nm and 1400 nm (near infrared, NIR) were observed. It is found that fluorine additive weakly affects PL detail of as deposited samples. However, hydrogen loading completely deactivates NIR PL in the case of fluorine free sample, but only slightly suppresses the NIR band in fl…
Growth and optical characterization of indirect-gap AlxGa1−xAs alloys
1999
Nonintentionally doped AlxGa1−xAs layers with 0.38 x 0.84 were grown on (100) GaAs substrates by liquid phase epitaxy (LPE) under near-equilibrium conditions. The crystalline quality of the samples was studied by photoluminescence at 2 K and room temperature Raman spectroscopy. The peculiar behavior in the photoluminescence intensities of the indirect bound exciton line and the donor–acceptor pair transition is explained from the evolution of the silicon donor binding energy according to the aluminum composition. It was also possible to observe the excitonic transition corresponding to the AlxGa1−xAs/GaAs interface, despite the disorder and other factors which are normally involved when gro…
Luminescence of non-bridging oxygen hole centers as a marker of particle irradiation of {\alpha}-quartz
2021
The origin of the "red" emission bands in the 600 nm-700 nm region, observed in quartz crystals used for luminescence dating and environmental dosimetry, is still controversial. Their reported spectral and lifetime characteristics are often similar to those of oxygen dangling bonds ("non-bridging oxygen hole centers, NBOHCs") in glassy silicon dioxide. The presence of these "surface radical type" centers in quartz crystal requires sites with highly disordered local structure forming nano-voids characteristic to the structure of glassy SiO2. Such sites are introduced in the tracks of nuclear particles ({\alpha}-irradiation, neutrons, ions). In case of electrons they are created only at large…
Optical properties of ZnO deposited by atomic layer deposition (ALD) on Si nanowires
2018
International audience; In this work, we report proof-of-concept results on the synthesis of Si core/ ZnO shell nanowires (SiNWs/ZnO) by combining nanosphere lithography (NSL), metal assisted chemical etching (MACE) and atomic layer deposition (ALD). The structural properties of the SiNWs/ZnO nanostructures prepared were investigated by X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopies. The X-ray diffraction analysis revealed that all samples have a hexagonal wurtzite structure. The grain sizes are found to be in the range of 7-14 nm. The optical properties of the samples were investigated using reflectance and photoluminescence spectroscopy. The study o…