Volume 92, Issue 6, 15 September 2002
Index of content:
- DEVICE PHYSICS (PACS 85)
92(2002); http://dx.doi.org/10.1063/1.1499979View Description Hide Description
Silica mesoporous films with low dielectric constant were successfully fabricated by a multiple-step sol–gel process. Various surface modifications were conducted to make the surface of the filmshydrophobicity, which was proved very effective to maintain the low dielectric properties of the films. The basic properties of the silicafilms were evaluated by atomic force microscopy, specular x-ray reflectivity, Fourier transform infrared, and thermal gravimetric and differential thermal analysis. An inherent low dielectric constant of around 2.0 was realized for about 56% porosity of the silicafilm with pore size less than 40 nm and the leakage current was at a level of after two months of fabrication. Preliminary results of the silicafilms prepared here present a very positive prospective to intermetal dielectric applications.
92(2002); http://dx.doi.org/10.1063/1.1503174View Description Hide Description
Previously, the authors have described a method of dynamically stabilized noncontact electromagnetic suspension of rotating bodies. The method makes use of the dynamic interaction between stationary and rotating sets of conductors and permanent magnets. The validity of this method has been demonstrated by building and testing a prototype in which noncontact suspension of a 3.2 kg rotor was achieved when it rotates at speeds above 18 Hz. A stability condition for that method of suspension was obtained with certain simplifying assumptions. One of these assumptions was that the inductive component of the stationary conductors is negligible. Here, we present modified stability conditions which take the inductance of the stationary conductors into consideration. One of the predicted effects is that nonzero inductance may cause significant reduction of the minimum stable levitation speed. Consequently, careful choice of the electrical properties of the stationary coils may significantly enhance the performance of the suspension.