Silicon carbon overcoating

The atomic% substrate in the spectrum is then the sum of the substrate portions of the Cl and Ols integrated areas (plus the integrated area of the Si2p spectrum in the case of a non-carbon-overcoated silicon substrate). The ratio of the PFOM film... 

Since the air bearing surface of the slider is carbon-overcoated, the same carbon overcoat was placed on some of the silicon strips to evaluate the PFOM film thickness and ellipsometric measurement procedure on carbon- and non-carbon-overcoated substrates. A nominally 12.5-nm-thick layer of sputtered carbon was deposited on silicon strips, and the strips were dip coated with PFOM. The ellipsometric angles A and T were measured. The two-layer model (two films on an absorbing substrate) was used with the optical constants for the materials listed in table 4.6 in calculating the PFOM thickness from A and T on carbon-overcoated silicon. The apparent... 

Optical Constants from Ellipsometry and Ellipsometric Angles A and P for the Carbon-Overcoated Silicon Strips... 

PFOM Thickness on Carbon-Overcoated Silicon Strips as Measured by Ellipsometry and as Estimated from XPS d/X... 

Since an additional ellipsometric measurement would be needed to determine the carbon-overcoat thickness, the ellipsometric measurement of PFOM thickness directly on non-carbon-overcoated silicon is more straightforward. Silicon strips and wafers were dip coated with PFOM. The PFOM thickness measnred by ellipsometry and the dIX from XPS are listed in table 4.8. The thickness measured by ellipsometry was divided by the dIX from XPS for each sample (last two columns in table 4.8). The experimentally determined average electron mean free path for PFOM film is X = 2.66 nm. Sliders were dip coated with PFOM at the same conditions as the silicon wafers and strips, and dIX was measured on the air bearing surface of each slider by XPS. These dIX were multiplied by A, = 2.66 nm, as determined above, to estimate the PFOM thickness on the air bearing surface. These results are listed in table 4.9. The concentration of the PFOM solution was 650 ppm, and the withdrawal rate was 1.6 mm/s. 

A test was done to evaluate the use of non-carbon-overcoated silicon wafers and strips as PFOM thickness monitors. The PFOM thickness on the silicon wafers and strips is shown in table 4.8 along with the dfX from XPS measured on the same samples. The data in table 4.8 were employed to derive the experimental mean free path relating PFOM thickness from eUipsometry with dJX from eq. (4.1) as... 

The electron mean free path of A, = 2.66 nm is within the range of mean free paths reported for polymer thin films on surfaces [8]. Equation (4.4) was used to estimate the PFOM thickness on air bearing surfaces from dIX. The values of dIX and PFOM film thicknesses are given in table 4.9. The PFOM film was 0.5-0.7 nm thicker on the carbon-overcoated air bearing surfaces (table 4.9, column 3) and on the carbon-overcoated rows (table 4.7, columns 3 and 7) than on the silicon wafers (table 4.8, column 3). This is attributed to the difference between the surface chemistry of the SiOj surface of the uncoated silicon and that of the carbon overcoat. 

The fuel for the Peach Bottom reactor consisted of a uranium-thorium dicarbide kernel, overcoated with pyrolytic carbon and silicon carbide which were dispersed in carbon compacts (see Section 5), and encased in graphite sleeves [37]. There were 804 fuel elements oriented vertically in the reactor core. Helium coolant flowed upward through the tricusp-shaped coolant channels between the fuel elements. A small helium purge stream was diverted through the top of each element and flowed downward through the element to purge any fission products leaking from the fuel compacts to the helium purification system. The Peach... 

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