Oxidized and unoxidized silicon

Fig. 5 Calculated curves eharacterizing the relation between the refractive index of oxidized porous silicon and the degree of oxidation of the silicon base layer, X = 632.8 nm. The Si + Si02 curve corresponds to a film in which no voids are left after oxidation is the initial porosity of the unoxidized film (Data from Astrova et al. 1999)...

Si/SiOi Interface. There is little information on the interface of silicon and an anodic oxide film. For thermally grown oxides, a transition region exists at the Si/Si02 interface where there is an excess of unoxidized Si bonds with a density on the order of the surface atom density. The interface structurally consists of two distinct regions. A few atomic layers near the interface contain Si atoms in intermediate oxidation states, i.e., Sf (Si20), Si (SiO), and Si (Si203). The S atoms are located farther out than... 

XPS was used by Brewis et al [58] to determine the levels and nature of oxidation in carbon fiber. ESCA revealed the presence on the carbon fiber surface of =C==0, =C—OH, Na, —S04, =C=C=, unoxidized nitrogen and silicone type Si. A direct relationship was found to exist between carbon fiber stability and the sodium present as Na2S04 (Figure 12.31). Figure 12.32 shows selected ESCA spectra [59]. 

Fig. 6 The porosity versus the refraetive index of oxidized porous silicon, calculated for various initial porosities pin of the unoxidized film, 1 = 632.8 nm. The dot-dashed curves representing Si + V (porous silicon) and Si02 + V (porous oxide) bound the region of values having physical significance Pin is determined from the point of intersection of the p-n curve with the Si + V curve (Data from Astrova and Tolmachev 2000)...

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