Optical properties of amorphous carbon measured with reflection electron energy loss spectroscopy spectra

2021 ◽  
Author(s):  
Lihao Yang ◽  
Jiamin Gong ◽  
Attila Sulyok ◽  
Miklos Menyhard ◽  
György Sáfrán ◽  
...  
Keyword(s):  
Optical Properties ◽  
Energy Loss ◽  
Electron Energy ◽  
Amorphous Carbon ◽  
Electron Energy Loss Spectroscopy ◽  
Cylindrical Mirror ◽  
Theoretical Investigations ◽  
Electron Energy Loss

We present the combined experimental and theoretical investigations of optical properties of amorphous carbon. The reflected electron energy loss spectroscopy (REELS) spectra of carbon were measured with a cylindrical mirror...

Derivation of Optical Properties of Carbonaceous Aerosols by Monochromated Electron Energy-Loss Spectroscopy

2014 ◽  
Vol 20 (3) ◽  
pp. 748-759 ◽  
Author(s):  
Jiangtao Zhu ◽  
Peter A. Crozier ◽  
Peter Ercius ◽  
James R. Anderson
Keyword(s):  
Optical Properties ◽  
Energy Loss ◽  
Electron Energy ◽  
Amorphous Carbon ◽  
Electron Energy Loss Spectroscopy ◽  
Radiative Forcing ◽  
Accurate Determination ◽  
Carbonaceous Aerosols ◽  
Carbonaceous Particles ◽  
Electron Energy Loss

AbstractMonochromated electron energy-loss spectroscopy (EELS) is employed to determine the optical properties of carbonaceous aerosols from the infrared to the ultraviolet region of the spectrum. It is essential to determine their optical properties to understand their accurate contribution to radiative forcing for climate change. The influence of surface and interface plasmon effects on the accuracy of dielectric data determined from EELS is discussed. Our measurements show that the standard thin film formulation of Kramers−Kronig analysis can be employed to make accurate determination of the dielectric function for carbonaceous particles down to about 40 nm in size. The complex refractive indices of graphitic and amorphous carbon spherules found in the atmosphere were determined over the wavelength range 200–1,200 nm. The graphitic carbon was strongly absorbing black carbon, whereas the amorphous carbon shows a more weakly absorbing brown carbon profile. The EELS approach provides an important tool for exploring the variation in optical properties of atmospheric carbon.

Electron Energy Loss Spectroscopy (EELS) of Iron Fischer–Tropsch Catalysts

2006 ◽  
Vol 12 (2) ◽  
pp. 124-134 ◽  
Author(s):  
Yaming Jin ◽  
Huifang Xu ◽  
Abhaya K. Datye
Keyword(s):  
Iron Oxide ◽  
Energy Loss ◽  
Electron Energy ◽  
Amorphous Carbon ◽  
Electron Energy Loss Spectroscopy ◽  
Iron Carbide ◽  
Iron Catalysts ◽  
Fischer Tropsch ◽  
Iron Phase ◽  
Electron Energy Loss

Electron energy loss spectroscopy (EELS), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy have been used to study iron catalysts for Fischer–Tropsch synthesis. When silica-containing iron oxide precursors are activated in flowing CO, the iron phase segregates into iron carbide crystallites, leaving behind some unreduced iron oxide in an amorphous state coexisting with the silica binder. The iron carbide crystallites are found covered by characteristic amorphous carbonaceous surface layers. These amorphous species are difficult to analyze by traditional catalyst characterization techniques, which lack spatial resolution. Even a surface-sensitive technique such as XPS shows only broad carbon or iron peaks in these catalysts. As we show in this work, EELS allows us to distinguish three different carbonaceous species: reactive amorphous carbon, graphitic carbon, and carbidic carbon in the bulk of the iron carbide particles. The carbidic carbon K edge shows an intense “π*” peak with an edge shift of about 1 eV to higher energy loss compared to that of the π* of amorphous carbon film or graphitic carbon. EELS analysis of the oxygen K edge allows us to distinguish the amorphous unreduced iron phase from the silica binder, indicating these are two separate phases. These results shed light onto the complex phase transformations that accompany the activation of iron catalysts for Fischer–Tropsch synthesis.

Local Electronic Structure Of Defects In Gan From Spatially Resolved Electron Energy-Loss Spectroscopy

1997 ◽  
Vol 482 ◽  
Author(s):  
M. K. H. Natusch ◽  
G. A. Botton ◽  
R. F. Broom ◽  
P. D. Brown ◽  
D. M. Tricker ◽  
...  
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Crystal Defects ◽  
Vacuum Field ◽  
Spatially Resolved ◽  
Local Electronic Structure ◽  
Electron Energy Loss

AbstractThe optical properties and their modification by crystal defects of wurtzite GaN are investigated using spatially resolved electron energy-loss spectroscopy (EELS) in a dedicated ultra-high vacuum field emission gun scanning transmission electron microscope. The calculated density of states of the bulk crystal reproduces well the features of the measured spectra. The profound effect of a prismatic stacking fault on the local electronic structure is shown by the spatial variation of the optical properties derived from low-loss spectra. It is found that a defect state at the fault appears to bind 1.5 electrons per atom.

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