Browsing by Subject "Silicon dioxide layers"

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    Electrical circuit modeling of surface structures for X-ray photoelectron spectroscopic measurements
    (Elsevier BV * North-Holland, 2008) Tasci, T. O.; Atalar, Ergin; Demirok, U. K.; Süzer, Şefik
    We model the X-ray photoelectron spectrometer and the sample with lumped electrical circuit elements, and simulate various types of conditions using a widely used computer program (PSpice) and compare the results with experimental measurements. By using the electrical model simulations, the surface voltage and the spectrum can be estimated under various types of external voltage stimuli, and the zero potential condition can be predicted accurately for obtaining a truly uncharged spectrum. Additionally, effects of several charging mechanisms (taking place during XPS measurements) on the surface potential could easily be assessed. Finally, the model enables us to find electrical properties, like resistance and capacitance of surface structures, under X-ray and low-energy electron exposure.
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    ItemOpen Access
    Synthesis and size differentiation of Ge nanocrystals in amorphous SiO 2
    (Springer, 2006) Aǧan, S.; Çelik-Aktaş, A.; Zuo, J. M.; Dana, A.; Aydınlı, Atilla
    Germanosilicate layers were grown on Si substrates by plasma enhanced chemical vapor deposition (PECVD) and annealed at different temperatures ranging from 700-1010 °C for durations of 5 to 60 min. Transmission electron microscopy (TEM) was used to investigate Ge nanocrystal formation in SiO 2:Ge films. High-resolution cross section TEM images, electron energy-loss spectroscopy and energy dispersive X-ray analysis (EDX) data indicate that Ge nanocrystals are present in the amorphous silicon dioxide films. These nanocrystals are formed in two spatially separated layers with average sizes of 15 and 50 nm, respectively. EDX analysis indicates that Ge also diffuses into the Si substrate.