Comparison of photo- and plasma-assisted passivating process effects on GaAs devices by means of low-frequency noise measurements

Fluctuation-Enhanced Sensing (FES): A Promising Sensing Technique

“…The solution of employing electrical noise (spontaneous fluctuations) to identify chemical agents was first proposed by Bruschi and coworkers [41,42] in 1994-1995 by showing the high sensitivity of conductance noise spectra of conducting polymers to the ambient gas composition. Gottwald and coworkers [43], a few years later (1997), also published similar observations about the conductance noise spectra of semiconductor resistors with non-passivated surfaces. In 1998, Kish and coworkers designed the first FES system capable of quantitative analysis of gas mixtures and conducted mathematical analysis about the limits and the sensor number requirement versus the number of agents [44][45][46].…”

“…To generate a separate pattern corresponding to different chemical compositions, like in the case of electronic noses, a number of different types of sensors are needed, which makes the system expensive and unreliable for practical applications. On the other hand, fluctuation-enhanced sensing (FES), as illustrated in Figure 3, by analyzing the fluctuations rather than the DC value, is capable of generating complex patterns even by starting from a single sensor [41][42][43][44][45][46][47][48] and this fact represents a great advantage with respect to other more conventional sensing techniques. When applying FES, instead of using the mean value (time average) of the sensor signal, the small stochastic fluctuations around the mean value are amplified and statistically analyzed.…”

“…Suppose the power density spectrum of the resistance fluctuations in a FES sensor has K different frequency ranges, in which the dependence of the response on the concentration of the chemical species is different from the response in the other ranges, one can write [43][44][45]:…”

Study of thermally grown and photo-CVD deposited silicon oxide–silicon nitride stack layers

“…Conventionally, the lower oxide is thermally grown and the upper nitride layer is deposited by low temperature deposition technique in an ON structure [11]. Although low temperature deposition is mainly achieved by the conventional parallel plate, in the case of capacitively coupled rf-PECVD method with 13.56 MHz rf radiation as the energy source, radiation-induced damage could be a serious disadvantage [12,13]. Photo CVD could be an attractive alternative to PECVD as a low temperature deposition technique [14].…”

Investigation of structural properties of high‐rate deposited SiNx films prepared at low temperatures (100–300 °C) by atmospheric‐pressure plasma CVD

“…Silane (SiH 4 ) and ammonia (NH 3 ) are commonly used as source gases in the temperature range of 200-400 °C. In conventional PECVD processes, although the deposition rate increases with increasing power density and/or gas pressure, the film properties tend to deteriorate due to the introduction of pinholes and electrically active defects [10,11], which are mainly caused by energetic ions in the plasma. Thus, the practical deposition rate is limited at approximately 5 nm/s or less.…”