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.
Humidity Sensors for High Energy Physics Applications: A Review
Modern silicon-based detectors for high-energy physics operate in an experimental environment with sub-zero temperatures. At those temperatures, even low traces of humidity will produce vapor condensation with damages to the detectors. Monitoring relative humidity is then a requirement for efficient detector operation. However, the performance of any relative humidity sensor operating in high-energy physics detectors is highly degraded in time due to high radiation doses. Therefore, this paper provides a comprehensive review of all the humidity sensors that have been tested so far for use in high-energy physics applications. Different working-principles of the tested humidity sensors are introduced as well as the description of the radiation effects on the sensing materials. Actually, there are only few publications in literature about humidity sensors as related to this novel and challenging application, while it becomes increasingly important to keep under control the performance-degradation of any silicon-based detector in most advanced high-energy physics.
Growth of Crystal Silicon Films from Chlorinated Silanes by RF Plasma-Enhanced Chemical Vapor Deposition
Low-temperature growth of crystal silicon films is demonstrated from chlorinated silane, i.e., SiH2Cl2, SiHCl3 and SiCl4, with hydrogen dilution by a RF glow-discharge method. Low-temperature crystallization is significantly enhanced on amorphous substrates such as glass from the initial growth stage in all systems. In the SiH2Cl2 system, however, the film crystallinity strongly depends on deposition parameters, i.e., substrate temperature, Ts, and the flow rate of hydrogen, Fr(H2). On the other hand, it is almost independent of Ts and Fr(H2) in the SiCl4 system. This difference originates from the chemical reactivity of deposition precursors and the corresponding surface reaction. Low-temperature crystallization from SiH2Cl2 and SiCl4 systems is discussed through studies on the film growth combined with the in situ monitoring of the surface reaction using Fourier transform infrared reflection absorption spectroscopy (FTIR-RAS).