Papers by Keyword: Cathodoluminescence

Abstract: The aim of this work is study of point defects modification in silicon dioxide by a high power density electron beam. In this work we used the method which allows to estimate quantitative content of luminescent point defects by dependence of cathodoluminescence on current density. Content of point defects was evaluated and changing of point defect content in silicon dioxide under electron beam was assessed. It is shown that content of defect connected with silicon deficit decreases whereas content of defect connected with oxygen deficit increases. The model of point defects transformation was suggested on the basis of these results.

Abstract: We report on 0.93 eV luminescence observed in multicrystalline silicon. The spectral line is close to the well known D3 one, but its properties are different. The new feature shows a remarkable intensity at room temperature, exceeding the intensity of the band to band radiative transition. Moreover, it appears as a single line in the entire temperature range 10-300K, in contrast to the D3, which is usually accompanied by D4. Cathodoluminescence (CL) and electron beam induced current (EBIC) micrographs revealed that the centers causing 0.93 eV emission are irregularly distributed along certain grain boundaries. Electron backscattering diffraction examination showed that the 0.93 eV luminescence appears at grain boundaries characterized by a lattice rotation around a <344> axis. The EBIC contrast at those irregularities indicates strong total recombination. Based on an analysis of the temperature dependence of the CL intensity and the EBIC contrast we obtained an activation energy of about 120 meV.

Abstract: In this paper the effect of unstable luminescence in nitrides was studied, notably the phenomena of cathodoluminescent intensity rising under stationery electron beam irradiation with typical times of tens up to hundreds of seconds. Long-lasting impact by electron beam leads to changes of cathodoluminescence properties of irradiated area. The changes still remain even after keeping structures at room temperature for several days. Reversibility of this "memory effect" was examined. A model of effect observed was proposed and experimentally verified.

Abstract: In this paper, the phosphor La2O3: Dy3+ was synthesized by a gel-sel method and its structure, morphology, particle size, Photoluminescence (PL) and Cathodoluminescence (CL) properties were characterized by X-Ray powder diffraction (XRD), scanning electron microscopy (SEM),laser particle size analyzer, Photoluminescence (PL) and Cathodoluminescence (CL) spectra, respectively. The results indicate that the Dy3+ as luminescent centers substituted La3+ ions into the single crystal lattice of La2O3 and located in the sites of C3. The size of particles was nearly spherical with the diameter of about 1μm. The sample can be 350~500nm light into visible light. Whether Photoluminescence (PL) or Cathodoluminescence (CL), Two emission peaks at about 489 nm (blue) and 575 nm (yellow) were corresponding to 4F9/2-6H15/2 and 4F9/2-6H13/2 transitions with the maximum emission wavelength at about 575 nm. This white phosphor can be applied both in LEDs and in the field emission devices.

Abstract: The ZnO thin films have been produced on p-type Si and quartz substrates by the spin-coating method and after deposition were heated at different temperatures in the range from 650K to 850K. The photoluminescence (PL) and cathodoluminescence (CL) measurements were carried out at temperature range 12K-350K. I-V, C-V measurements were performed on the Al/ZnO/Si/Al structures at different temperatures. The structural properties of the ZnO thin films were carried out using x-ray and SEM method. The effects of the thickness variation and annealing temperature on the crystallinity parameters were observed. The electrical response of grains, grain boundaries, and contacts of the ZnO film was obtained.

Abstract: GaN crystals grown in supercritical ammonia by the ammonothermal method were studied by cathodoluminescence (CL), both in image and spectrally resolved modes. The main extended defects and the incorporation of point defects and impurities in different growth sectors were revealed. The influence of the seeds, the role of the growth planes and the changes in the crystal quality during the growth run are discussed.

Abstract: Cathodoluminescence (CL) in SEM and electroluminescence (EL) techniques are widely used for investigation of optical properties of electronic structures. It is assumed that the CL signal represents the local properties of the region irradiated by the electron beam. However, this assumption is true if there is no electric field in the excitation region. In the opposite case the electron-hole pairs generated by the electron beam are separated by the electric field and the local voltage source is generated. The voltage is distributed all over the structure through resistance paths and it causes a current flow, which presence affects the registered CL signal. A range of this effect depends on the resistance distribution within the structure and on the value of electron beam current. The range may be much longer than the diffusion length of minority carriers. When EL signal is measured in SEM, it represents the mean properties of the whole structure. The comparison of the CL results with the EL ones detected in SEM gives valuable information about the examined structures, as will be shown in the present investigations. The AlGaAs/GaAs heterostructures with 8 nm InGaAs quantum well have been examined. For that aim also special test structures for CL and EL measurements have been formed on standard epitaxial structures.

Abstract: According to different light sources and cathodoluminescence (CL) intensity, the performance of color parameters (lightness L^*, chromaticity a^* and b^*, chroma C^*, hue angle h_o) and chromophore contents (Cr³⁺, åFe) are studied to analyze the impact of all these elements on ruby red color. Ruby red under the standard light source D65 (a^*=5.65 ~ 26.97, b^*= -5.43~3.98) is similar with the color under natural sun-light. Purplish red h_o Î (354.14°, 0.7°) with medium-low lightness (L^* = 32 ~ 40) under D65 displays the best visual appearance, showing a relatively high value. Comparing with D65, standard light source A reveals ruby a deep red hue (a^* = 10.61 ~ 37.39, b^* = -6.59 ~ 7.50). Because of the strongest spectrum power distribution in the orange range and fluorescence of light source U30, the hue of orangish tone is mixed in ruby red (a^* = 6.92 ~ 31.23, b^* = 0.31 ~ 9.34). It is illustrated that åFe can inhibit the intensity of CL which is compared in different voltages. Low lightness purplish red is easy to be influenced by CL and always shows strong luminescence correspondingly. It is concluded that ruby purplish red has strong luminescence of CL which is usually supported by a few of åFe and medium-low lightness under D65, which has an excellent visual perception.

Abstract: This study focus on the nature of different Si-based sensitizers for Er³⁺ ions in Silicon- Rich Silicon oxide thin films. The samples were first analyzed by Cathodoluminescence technique to probe all emitting centers in the films. Some of these centers were found to be potential sensitizers for Er³⁺ ions, such as Silicon Oxygen Deficient Center and Non-Bridging Oxygen Hole Center, in addition to the well-known Silicon-nanoclusters (Si-nc). The influence of the thickness was subsequently examined, revealing that the formation of Si-nc is inhibited for films thinner than 100 nm and this led to less sensitization of the Er³⁺ ions. We demonstrate that the introduction of a SiO₂ buffer layer can overcome this issue and increase the luminescence of Er³⁺ ions by a factor of five for films thinner than 50 nm that are usually used for electrically-driven photonic devices.

Abstract: The dislocation-related luminescence (DRL) in the vicinity of D1 band (0.8 eV) in hydrophilically bonded n- and p-type silicon wafers is investigated by means of recently developed pulsed trap refilling enhanced luminescence technique (Pulsed-TREL). The shallow and deep dislocation related electronic states in both upper and lower part of the band gap are determined and characterized by means of DLTS. Among those traps we have established ones which directly participate in D1 DRL. We have shown that D1 luminescence goes via shallow dislocation related states (SDRS) located close to the conduction and valence bands with thermal activation energy of about 0.1 eV whereas deep levels do not participate in D1 DRL. The model explaining the fact how the 0.8 eV luminescence may go through levels which interlevel energy is at least 0.97 eV in terms of Coulomb interaction between ionized SDRS is suggested.