Nanocrystalline Si-Based Resistive Humidity Sensors Prepared via HWCVD at Various Filament Temperatures
The growth of nanocrystalline Si on glass substrates via hot-wire chemical vapor deposition (HWCVD) at various filament temperatures and the fabrication of nanocrystalline Si-based resistive humidity sensors are reported. Experimental results indicate that the average diameter of nanocrystalline Si particles increases with increasing filament temperature. Measurements of the resistivity change of samples with humidity at 25°C show that the sensor response of samples fabricated at high filament temperatures is lower than that of samples fabricated at low filament temperatures. The sensitivity of the sensor increases with relative humidity.
Radio-Frequency Inductors on High-Resistivity Silicon Substrates with a Nanocrystalline Silicon Passivation Layer
In this paper, spiral inductors on high-resistivity silicon (HR-Si) substrates, which surfaces were passivated by different process methods, were fabricated and measured. The comparison of inductances and quality factors between these inductors shows that the inductances and quality factors of spiral inductors significantly depend on process method and thickness of surface passivation layer. The differently generated passivation layer results in different effective substrate resistivity and hence gives rise to different substrate loss. The experimental results show that using thicker nanocrystalline silicon (nc-Si) as a passivation layer will result in a smaller substrate loss and hence spiral inductors on the substrate have larger inductances and larger quality factors. In this study, the metal thickness of inductors is 1.2 µm and is about half that of the inductors provided by foundries. At higher frequencies, the thinner spiral inductors on the SiO2/nc-Si/HR-Si substrate have larger inductances and larger quality factors as compared with the inductors provided by foundries. With the same metal thickness as that adopted in standard processes of foundries, the identical-geometry inductors on the SiO2/nc-Si/HR-Si substrate probably exhibit superior quality factors.
Ratzel, the French School and the birth of Alternative Geopolitics
Abstract Modern French political geography began as a response to Ratzel's Politische Geographie and then became an attempt to place ratzelian ideas into the context of French geographical thought. What then emerged was a political geography which was set firmly in opposition to German geopolitics. There were some geographers who felt that a more effective response could be made by developing an indigenous French geopolitics. This can be seen as being the origin of the alternative geopolitics which was favoured by some American geographers during and after World War II and which subsequently became an important underlying theme in the new geopolitics which arose in the 1970s. The concept of an alternative geopolitics has owed a great deal to the French school of geography and has it roots in the original response of Vidal de la Blache to Ratzel.