Browsing by Subject "Thickness measurement"
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Item Open Access A parametric analysis of finite phased arrays of printed dipoles on large circular cylinders and comparisons with the planar case(IEEE, 2004-06) Güner, B.; Ertürk Vakur B.; Bakır, O.A parametric study of finite phased arrays of printed dipoles on electrically large coated cylinders is performed using a spatial domain hybrid MoM/Green's function technique. Dipole currents and several performance metrics like active reflection coefficient and input impedances of the dipoles are calculated and compared with their planar counterparts. The effects of the curvature, dipole orientation and changes in the array and host body parameters are observed and discussed.Item Open Access XPS studies of SiO2/Si system under external bias(American Chemical Society, 2003) Ulgut, B.; Süzer, ŞefikThermally grown SiO2 layers on Si (100) substrate have been subjected to different external voltage bias during XPS analysis to induce changes in the measured binding energy difference between Si4+ and Si0 in Si2p and SiKLL regions. The Si2pp binding energy difference increases from 3.2 to 4.8 for samples containing 1-7 nm oxide thickness, and furthermore, this difference can be influenced by application of an external bias to the sample. Application of negative d.c. bias increases the binding energy difference, whereas positive bias decreases it. The voltage dependence of the binding energy difference exhibits a sigmoid character with an abrupt change near 0 V. Both the binding energy difference and differential change between the positive and negative bias have similar functional dependence on the thickness. This is attributed to differential charging between the silicon oxide layer and silicon substrate, which is decreased when a positive bias is applied to the sample (and therefore attracting a larger proportion of the stray electrons from the vacuum chamber to partially neutralize the oxide). Similarly, when negative bias is applied, the stray electrons are repelled from the sample resulting in less neutralization and an increased differential charging. Through external biasing, it is determined that charging in the SiO2/Si system persists all of the way down to 1 nm. Application of a.c. (square-wave) bias is equivalent to simultaneous application of negative and positive bias together. However, the differential change in the binding energy difference in the positive and negative cycle is frequency dependent and approaches to the d.c. results at lower frequencies.