Optical band-gap materials

CL is a powerful tool for the characterization of optical properties of wide band-gap materials, such as diamond, for which optical excitation sources are not readily available. 

As mentioned earlier, CL is a powerful tool for the characterization of optical properties of wide band-gap materials, such as diamond, for which optical excitation sources are not readily available. In addition, electron-beam excitation of solids may produce much greater carrier generation rates than typical optical excitation. In such cases, CL microscopy and spectroscopy are valuable methods in identifying various impurities, defects, and their complexes, and in providing a powerful means for the analysis of their distribution, with spatial resolution on the order of 1 pm and less. ... 

The hard carbon produced by this method has a range of different properties from those of plasma produced films (Table V). Note that the maximum band gap achievable with ICBD is 1.2eV at maximum hydrogenation (35 atomic %) while values up to 4eV can be obtained by plasma deposition. These wide band-gap materials are soft and easily scratched though they are more optically transparent. 

In Chapter 5.4, optical ultraviolet radiation sensors are described, including UV-enhanced silicon-based pn diodes, detectors made from other wide band gap materials in crystalline or polycrystalline form, the latter being a new, less costly alternative. Other domestic applications are personal UV exposure dosimetry, surveillance of sun beds, flame scanning in gas and oil burners, fire alarm monitors and water sterilization equipment surveillance. 

The recently synthesized PPV 68, in which the oxadiazole group is separated from the PPV backbone by an oxygen atom, is a very soluble material with optical band gap of 2.36 eV and yellowish-orange emission color (chromaticity coordinates by the Commission Internationale de l Eclairage, CIE a 0.50, y = 0.47 591 nm) [124]. An extremely high-... 

The EL of poly(o-phenylene ethynylene) 522 was reported by Onoda and coworkers [637], As expected, the optical band gap of 522 (3.1 eV) is larger than that of para-connected polymer 516, making the former a blue-purple-emitting material (APL = 400). Interestingly,... 

Match the optical band gap of the emitters. The materials should avoid light absorption and scattering to maximize light output and increase the efficiency. 

The activity of these materials was attributed to the ability to promote multiple electron transfer for 02 evolution and the presence of at least partially separated oxidation and reduction sites [108]. Their major drawback is the high optical band-gap, which in several cases is over 4.0 eV (7 < 310 nm). 

A chemical reaction occurs above 1.5 GPa The sample turns black, new peaks develop in the Raman spectrum, and the absorption edge moves below 11,000cm. The recovered material has an optical band gap of 1.39eV, smaller than the band gap of polyacetylene. From the analysis of the Raman spectrum, it is seen that the C=C stretching mode completely disappears in the reaction product, while the C=N stretching band is present but at a different frequency than in cyanocetylene. In addition, the Raman bands of polyacetylene are observed with their characteristic frequency dependence on the wavelength... 

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