Papers by Keyword: Cathodoluminescence

Abstract: Aluminum nitride (AlN) ceramics with various amounts of Ca3Al2O6 (C3A) as a sintering additive were sintered at 1880°C for 50 h in N2 atmosphere. The thermal conductivity of AlN ceramics increased with increasing amount of C3A in the range from 0.5 to 4.8 mass%. Cathodoluminescence (CL) intensity attributed to oxygen-induced defects decreased with increasing amount of C3A. From the results, the increase of the thermal conductivity was considered to relate to the decrease of the oxygen-induced defects by increasing amount of C3A.

Abstract: Alpha aluminum oxide (α-Al2O3) ceramics was coupled and reacted with zinc oxide (ZnO) ceramics at 1200°C for 24 h. Energy dispersive X-ray spectroscopy (EDS) analysis revealed the existence of step-shaped distribution of Al and Zn near the interface between α-Al2O3 and ZnO. Intense ultraviolet (3.75 eV) emission was clearly observed from the layer. On the other hand, very weak emissions were observed outside the layer near the interface. The compound in the layer is considered to be an attractive material for ultraviolet optoelectronics.

Abstract: In order to clarify the fundamental luminescent mechanism of undoped and Er-doped ZnO thin films synthesized by sputtering method, cathodoluminescence (CL) from the samples formed on several kinds of substrate were measured. There was no explicit peak identified with luminescence from ZnO crystal defects in undoped sample, on the contrary, three sharp luminescent peaks were observed in the case of Er-doped ZnO film due to the internal transition of the additive Er ions in the CL spectrum. The mechanism was investigated in comparison with photoluminescence (PL).

Abstract: Beta gallium oxide (β-Ga2O3) crystals were grown on β-Ga2O3 ceramics heated by electric current under vacuum at various ambient temperatures. From cathodoluminescence at room temperature, emission peaks at 2.9 and 3.5 eV were clearly observed. With increasing ambient temperature, the relative intensity of ultraviolet emission (3.5 eV) to blue emission (2.9 eV) showed a peak at 400oC. These results suggest that the ambient temperature during the electric current heating of β-Ga2O3 ceramics in vacuum is one of the most effective factors for the ultraviolet emissive β-Ga2O3 crystal.

Abstract: Copper aluminum disulfide (CuAlS2) powders were synthesized in an evacuated ampoule at elevated temperatures. X-ray diffraction analysis revealed that the powders heated at temperatures higher than 800oC were single-phase CuAlS2. In the cathodoluminescence (CL) spectra measured at room temperature, the powders heated at temperatures higher than 600oC exhibited a visible emission peak at approximately 1.8 eV and a distinct ultraviolet emission peak at 3.45 eV. The powder heated at 700oC showed the maximum intensity of ultraviolet emission which is considered to be associated with excitons.

Abstract: During interaction between thin film SiO2 and electron beam with high power density, amorphous silicon dioxide modifies. Silicon nanoclusters are formed in radiated area. Result of this interaction is formation of Si/SiO2 nanocomposite. We studied modified SiO2 by TEM, microdiffraction and cathodoluminescence.

Abstract: In this work we studied the cathodoluminescence (CL) of thin silicon oxide and natural silicon oxide grown on different types of silicon substrates (p-silicon and n-silicon with different content of boron and phosphor). At the same time we studied the distribution of intrinsic defects on depth for thermal silicon oxide films with depth resolution 10-20 nm. The method of local cathodoluminescence was used for definition the structure defects in SiO2 think layer and control of the quality of SiO2-Si interface.

Abstract: An overview is given of our recent research achievements in nano-scale stress microscopy based on cathodoluminescence (CL) piezo-spectroscopy (PS) studies of ceramics. The main underlying concepts of CL nano-scale microscopy are presented, with emphasis placed on the spatial resolution of the electron probe operating at low voltages in a field-emission gun scanning electron microscope (FEG-SEM). The stress assessment technique shown here proves its general validity independent of the physical mechanisms behind the CL emission. A table, including CL spectra from impurities, defects and electron-hole recombination, is given of the stress dependence of the wavelength of selected CL bands from various ceramics of industrial use, including a reliability assessment of these dependences. Finally, some applications of nano-scale stress microscopy are shown and brief comments are offered regarding possible future evolutions and impacts on the development of new materials and devices.

Abstract: Many of the properties of Si-based ceramics, including their structural behavior, are strongly influenced by their micro/nanostructure and by the microscopic residual stress fields piled up during processing and/or usage. The electron beam, used as a sharp and reliable probe for high-resolution cathodoluminescence (CL) assessments, can routinely provide a suitable tool for assessing both the structural and the mechanical characteristics of Si-based ceramics on a sub-micrometer scale. Although the full development of stress-related CL techniques is still in embryo, we show here the possibility of assessing microscopic stress fields inside a field-emission gun scanning electron microscope (FEG-SEM). This new assessment takes advantage of the piezo-spectroscopic effect on selected bands of CL spectra and it is applied here to both β-silicon nitride (Si3N4) and β-silicon carbide (SiC) ceramics. CL spectra in both materials arise from their peculiar optically active defects. Experimental assessments of microstress fields may open a completely new perspective in the development of high-performance Si-based ceramics because one can directly visualize how residual stresses distribute within the material micro/nanostructure and miniaturized devices.

Abstract: Electron-stimulated luminescence (cathodoluminescence, CL, henceforth) assessments can be quantitatively used in silicon-based optical devices for obtaining information about: (i) the residual stresses piled up during manufacturing; and (ii) the micro/nanoscopic structure of the device. In the present study, a quantitative characterization is presented from a micrometer to a nanometer scale using CL bands of some optically active defects existing within the nanostructure of optical devices. In particular, some CL bands, peculiar of oxygen-related defects in silica, have shown high stress sensitivity and thus were suitable for residual stress assessments. Knowledge of residual stresses can be quantitatively established from the examination of selected spectral shift characteristics (piezo-spectroscopic method). The correlation coefficient between stress and wavelength-shift of characteristic luminescence bands was systematically evaluated by stress calibrations. The piezo-spectroscopic approach shows promises as a valuable characterization tool, suitable for routinely inspecting micromechanical features and, thus, for optimizing low-loss, highquality optical devices.