Cathodoluminescence

About: Cathodoluminescence is a research topic. Over the lifetime, 8798 publications have been published within this topic receiving 153486 citations. The topic is also known as: cathode luminescence.

Structural Disorders in Gd2O2S:Tb Phosphors

Abstract: The luminescence characteristics of Gd2O2S:Tb phosphors prepared under different conditions are described and the possibility of electroluminescence discussed. X-ray diffraction and cathodoluminescence results are used to optimise synthesis parameters. The analysis of diffraction data for reflection intensity distribution from different (hkl) plane shows the presence of a disordered crystal structure. Brightness of luminescence emission is found to depend upon the extent of this disorder. The green cathodoluminescence is primarily due to the characteristic line emission 5D4-7F4 of Tb3+ in the spectral region of 540 nm. Under ac field excitation, the voltage dependence of electroluminescnece (EL) brightness follows the Destriau relation, B = B0 exp (-b/Vl/2).

Abnormal selective area growth of irregularly-shaped GaN structures on the apex of GaN pyramids and its application for wide spectral emission

Abstract: We report on the growth and the characterization of three-dimensional randomly-shaped InGaN/GaN structures selectively grown on the apex of GaN pyramids for the purpose of enlarging the emission spectral range. We found that the variations in the shape and the size of the three-dimensional GaN structures depend on the growth temperature and the surface area for selective growth under intentional turbulence in the gas stream. The selectively grown GaN structures grown at 1020 °C have irregular shape, while the samples grown at 1100 °C have rather uniform hexagonal pyramidal shapes. Irregularly shaped GaN structures were also obtained on the apex of GaN pyramids when the SiO2 mask was removed to 1/10 of the total height of the underlying GaN pyramid. When only 1/5 of the SiO2 mask was removed, however, the selectively grown GaN structures had similar hexagonal pyramidal shapes resembling those of the underlying GaN pyramids. The CL (Cathodoluminescence) spectra of the InGaN layers grown on the randomly shaped GaN structures showed a wide emission spectral range from 388 to 433 nm due to the non-uniform thickness and spatially inhomogeneous indium composition of the InGaN layers. This new selective growth method might have great potential for applications of non-phosphor white light emitting diodes (LEDs) with optimized growth conditions for InGaN active layers of high indium composition and with optimum process for fabrication of electrodes for electrical injection.

Thin film phosphor prepared by physical vapour deposition for FED application

Abstract: We fabricated ZnO:Zn film by rf magnetron sputtering and ZnS:Pr,Ce layer by electron-beam evaporation for color FED application. Also, in order to investigate influence of surface conductivity of phosphor film on the threshold voltage of emission, we fabricated two different kinds of layered structures having an additional conducting layer such as 5nm thick Sn-doped In/sub 2/O/sub 3/ film. CL emission spectrum of sputtered ZnO:Zn(250 nm) film shows a two broad peaks centered around 540 nm and 600 nm. The spectra characteristic of ZnS:Pr,Ce films shows white spectrum that covered a whole visible wavelength. One of the effects of an additional surface layer of ITO on ZnO and ZnS phosphor is the shift of spectrum toward shorter wavelength.

Study of the defects in GaN epitaxial films grown on sapphire by HVPE

Abstract: In this paper, the defects in hexagonal GaN epitaxial layers grown on (0001) sapphire (Al 2 O 3 ) substrates by HVPE with a horizontal tube reactor had been studied. The GaN epitaxial layers were etched by means of defect-selective etching (Orthodox etching in molten KOH). The samples were characterized by Scanning Electron Microscopy (SEM) and Cathodoluminescence spectra (CL). From surface morphology and cross-sectional images, the defects could be divided into various types: cracks, low angle grain boundary (LAGB), nano-pipes and dislocations. These different defects were discussed. The cracks were proposed as related to the strain. And the strain could not only come from the lattice mismatch and thermal mismatch between sapphire and GaN layer in their interface, but also from the HVPE growth process. It was found that these screw, mixed and edge type dislocations formed small hexagonal pits after etching. Some pits would be observed in the area near LAGB. Additionally, by CL mapping technique, some non-radiative recombination centers without surface terminations could be probed optically.

Electron Microscopy and Nanoscopy: Analytical

Abstract: The analytical electron microscope (AEM) is a transmission and/or scanning transmission electron microscope (S/TEM) which is modified to permit composition analyses using X-ray energy-dispersive spectroscopy (XEDS) and/or electron energy-loss spectroscopy (EELS) and energy-filtering TEM (EFTEM) as well as other analytical capabilities such as cathodoluminescence, holography, tomography, etc., in addition to its usual functions of imaging and diffraction. The versatility of AEM, combining high-resolution imaging, diffraction, and powerful analytical facilities (e.g., spectroscopic imaging), the variety of signals and contrast effects available in the course of electron beam specimen interactions, establish it as an outstanding characterization tool in many applications aimed for development of advanced nanotechnologies.