Search results for "Silicon"
showing 10 items of 1391 documents
Isoelectronic series of oxygen deficient centers in silica: experimental estimation of homogeneous and inhomogeneous spectral widths
2008
We report nanosecond time-resolved photoluminescence measurements on the isoelectronic series of oxygen deficient centers in amorphous silica related to silicon, germanium and tin atoms, which are responsible of fluorescence activities at approximately 4 eV under excitation at approximately 5 eV. The dependence of the first moment of their emission band on time and that of the radiative decay lifetime on emission energy are analyzed within a theoretical model able to describe the effects introduced by disorder on the optical properties of the defects. We obtain separate estimates of the homogeneous and inhomogeneous contributions to the measured emission line width, and we derive homogeneou…
Effect of impurities on Raman and photoluminescence spectra of AlN bulk crystals
2003
ABSTRACTRaman scattering and photoluminescence (PL) spectroscopy with sub-bandgap excitation has been applied to explore tracing of common impurities (in particular of oxygen) in AlN. Bulk AlN crystals grown by the high temperature sublimation method were studied. PL bands have been observed at around 375 nm and at 560–660 nm and have been attributed to oxygen and to nitrogen vacancy/aluminium excess defects, respectively. The 375 nm UV PL band was found to shift with oxygen concentration. Micro-Raman spectra of the bulk AlN samples were measured in different polarisations. Besides normal Raman modes of AlN the presence of additional vibrational modes was detected. The modes were discussed …
Intra-center and recombination luminescence of bismuth defects in fused and unfused amorphous silica fabricated by SPCVD
2013
Abstract Photoluminescence (PL) of bismuth doped silicon dioxide excited by UV excimer lasers (ArF — 193 nm, KrF — 248 nm) and a green light laser diode (532 nm) is studied in a wide spectral band at temperatures ranging from 12 to 750 K. Two types of samples are investigated: unfused, 100 μm in thickness amorphous layer immediately deposited on the inner surface of silica substrate tube, and the same material after profusion resulted from tube collapsing to a rod by external heating. PL bands centered at 620–650 nm, 820 nm and 1400 nm wavelengths are observed in both fused and unfused samples. Under excitation by the green laser diode decay time constants for 650 nm (orange) and 1400 nm (N…
Physical properties and applications of InxGa1−xN nanowires
2014
We have successfully grown InxGa1−xN nanowires by plasma-assisted molecular beam epitaxy on silicon substrates. The alloy composition and crystal quality have been analyzed by Raman scattering, photoluminescence spectroscopy and x-ray fluorescence nanoprobe techniques. InxGa1−xN is an one-mode alloy, where the different optical modes have an intermediate frequency of that of pure InN and GaN. The sample composition can be derived from the Raman data. On the other hand, by using the optical gap provided by the emission spectra, we conclude that the samples have a lower Ga content than that provided by the Raman analysis. X-ray fluorescence maps and photoluminescence measured in single nanowi…
Cathodo- and Photo- Luminescence of Silicon Rich Oxide Films Obtained by LPCVD
2012
Silicon technology dominates the electronics industry today, so it is highly desirable the development of silicon-based components compatible with silicon technology, allowing integration of electrical and optical components on a single chip. One promising approach to the development of a silicon based light emitter is Silicon Rich Oxide (SRO), also called offstoichiometric silicon oxide. The interest on the optical properties of this material has grown since it was demonstrated that SRO films subjected to high-temperature annealing exhibit efficient photoluminescence (PL) (Iacona et al., 2000; Shimizu-Iwayama et al., 1996).
Twofold coordinated Ge defects induced by gamma-ray irradiation in Ge-doped SiO2
2008
We report an experimental study by photoluminescence, optical absorption and Electron Paramagnetic Resonance measurements on the effects of exposure of Ge-doped amorphous SiO2 to gamma ray radiation at room temperature. We have evidenced that irradiation at doses of the order of 1 MGy is able to generate Ge-related defects, recognizable from their optical properties as twofold coordinated Ge centers. Until now, such centers, responsible for photosensitivity of Ge-doped SiO2, have been induced only in synthesis procedures of materials. The found result evidences a role played by gamma radiation in generating photosensitive defects and could furnish a novel basis for photosensitive pattern wr…
Recombination luminescence of oxygen-deficient centers in silica
2008
Abstract The luminescence of silica glass, prepared by plasma chemical vapor deposition (PCVD) and quartz glass of type IV (trade mark KS-4V) methods, were studied while irradiated with pulses of ArF laser (193 nm) light in the range of sample temperatures between 10 and 300 K. The samples contain less than 0.1 ppm metallic and hydroxyl impurities. The samples synthesized by PCVD were of two kinds. The first one (amorphous) was as-deposited from plasma at a substrate tube temperature of ∼1200 °C. The second one (fused) was prepared from the first by the tube collapsing with an external burner. In this process, a section of the substrate tube with the deposited glass was installed in a lathe…
Operation and first results of the NEXT-DEMO prototype using a silicon photomultiplier tracking array
2013
NEXT-DEMO is a high-pressure xenon gas TPC which acts as a technological test-bed and demonstrator for the NEXT-100 neutrinoless double beta decay experiment. In its current configuration the apparatus fully implements the NEXT-100 design concept. This is an asymmetric TPC, with an energy plane made of photomultipliers and a tracking plane made of silicon photomultipliers (SiPM) coated with TPB. The detector in this new configuration has been used to reconstruct the characteristic signature of electrons in dense gas, demonstrating the ability to identify the MIP and "blob" regions. Moreover, the SiPM tracking plane allows for the definition of a large fiducial region in which an excellent e…
Silicon Photomultipliers Signal-to-Noise Ratio in the Continuous Wave Regime
2014
Abstract— We report on Signal-to-Noise Ratio measurements carried out, in the continuous wave regime, at different bias voltages, frequencies and temperatures, on a class of silicon photomultipliers fabricated in planar technology on silicon p- type substrate. Signal-to-Noise Ratio has been measured as the ratio of the photogenerated current, filtered and averaged by a lock-in amplifier, and the Root Mean Square deviation of the same current. The measured noise takes into account the shot noise, resulting from the photocurrent and the dark current. We have also performed a comparison between our SiPMs and a photomultiplier tube in terms of Signal-to-Noise Ratio, as a function of the tempe…
Responsivity measurements of N-on-P and P-on-N silicon photomultipliers in the continuous wave regime
2013
We report the electrical and optical comparison, in continuous wave regime, of two novel classes of silicon photomultipliers (SiPMs) fabricated in planar technology on silicon P-type and N-type substrate respectively. Responsivity measurements have been performed with an incident optical power from tenths of picowatts to hundreds of nanowatts and on a broad spectrum, ranging from ultraviolet to near infrared (340-820 nm). For both classes of investigated SiPMs, responsivity shows flat response versus the optical incident power, when a preset overvoltage and wavelength is applied . More in detail, this linear behavior extends up to about 10 nW for lower overvoltages, while a shrink is observ…