Papers by Keyword: Electron Energy Loss Spectroscopy (EELS)

Abstract: Electron energy loss spectroscopy (EELS) and ab initio simulations are combined in this study to produce an atomistic interpretation of the interface morphology in lateral 4H-SiC / SiO₂ MOSFETs with deposited gate oxides. This allows the question of interface abruptness, and the presence the postulated SiO_xC_y interlayer to be explored for a subset of devices with deposited oxides. From comparison between EELS and ab initio calculation the interfaces considered are best described as abrupt, but stepped, transitioning without any of the carbon excess or SiO_xC_y interlayer that have been described for other devices observed.

Abstract: The microstructure and interface quality of chemical solution deposited barium titanate thin films on Ni foil were studied. Cross-sectional transmission electron microscopy shows that a ~200 nm thick barium titanate film annealed in a controlled oxygen partial pressure consists of equiaxed grains with grain size range of 24-75 nm (~ 42 nm average). NiO was detected after re-oxidation by X-ray diffraction, but not by transmission electron microscopy, suggesting that the oxide is not a continuous barrier layer, but is spatially distributed in the films. Oxygen non-stoichiometry and the existence of C in barium titanate films were observed by electron energy loss spectrometry. In addition, it was found that there is a 5-8 nm thick Ni-Ba alloy developed at the interface between the barium titanate film and Ni foil.

Abstract: Recently the present authors’ group found that porous silicon showed strong and stable white/white-blue light emission after successive thermal carbonization and oxidation by water vapor. This material can be considered as a price-competitive solid-state white-light source. We examined these layers by electron energy-loss spectroscopy (EELS), energy-filtering transmission electron microscopy (EFTEM). The EEL spectra indicated that the silicon skeleton in the porous layer was completely oxidized by the thermal treatment in wet argon ambient and multi-types of carbon phases were present in the 1073 K oxidized sample of stronger emission, while carbon complexes including Si and/or O were formed in the 1223 K oxidized sample of weaker light emission. EF-TEM images showed that carbon/oxygen were more uniformly distributed in the 1223 K oxidized sample. It is assumed that the strong light-emitting properties are controlled by the size and internal chemical bonding states of carbon clusters incorporated.

Abstract: Single-walled carbon nanotubes (SWNTs) have been synthesized on silicon nanowires (SiNWs) by ethanol chemical vapor deposition (CVD) using Co catalysts nanoparticles. The surface SiOx layers assist the formation of catalyst nanoparticles on SiNWs by inhibiting the diffusion of Co to Si. Co-Si compounds have formed in SiNWs readily when the surface SiOx layers are very thin. Therefore, the yield of SWNTs is strongly influenced by the thickness of the surface SiOx layers of SiNWs.

Abstract: Direct evidences of hydrogen loosely trapped between graphene layers in nanostructured graphite prepared by mechanical milling in a hydrogen atmosphere are presented, based on a combinational study of FT-IR, electron diffraction (ED) and electron energy-loss spectroscopy (EELS). The FT-IR spectrum of nanostructured graphite exhibited a new broad absorption band at very low frequencies around 660 cm-1, which almost disappeared by annealing up to 800 K. ED and plasmon peaks in EELS detected the unusual shrinkage and subsequent expansion of the fragmented graphene interlayer distance by hydrogen incorporation and desorption with annealing, well correlated with the change in intensity of the 660 cm-1 IR band. All the present results support our previous studies [S. Muto et al., Jpn. J. Appl. Phys. 44, 2061 (2005); T. Kimura et al, J. Alloys and Compounds 413, 150 (2006).].

Abstract: Polycrystalline diamond and diamond-like carbon (DLC) films were deposited by microwave chemical vapor deposition (MW-CVD) and by pulsed laser deposition (PLD) respectively. Ar ion bombardment was used to change the properties of these layers. The sp2 bonds were determined directly by reflected electron energy loss spectroscopy (REELS) and further characterization was made by Raman scattering. The polycrystalline diamond showed only very slight π-π* transition at 6.5 eV, but after Ar ion bombardment strong peak was formed but definitely shifted to lower energy compared to the well known π-π* transition of graphite. The as deposited PLD carbon films showed broad peak around 5eV clearly different than the π-π* transition (6.5eV). After Ar+ ion bombardment the peak was shifted also to lower energy range (4-5eV) with a remaining part at 6.5eV. The lower energy part of the peak can be correlated to the transition of sp3 sites, while this change in peak position was not detectable after ion bombardment of the reference HOPG sample, which does not contain sp3 hybridized carbon atoms.

Abstract: Interfacial atomic and electronic structures of Cu/Al2O3(0001) and Cu/Al2O3(11 ＿ ,20) prepared by a pulsed-laser deposition technique were characterized by high-resolution transmission electron microscopy (HRTEM) and electron energy-loss spectroscopy (EELS). It was found that both systems have O-terminated interfaces, irrespective of different substrate orientations. This indicates that Cu-O interactions across the interface play an important role for the Cu/Al2O3 systems.