Voltage controlled negative

Fig. 6.1. Classification of switching and memory characteristics, (a) Negative resistance device, (b) Negative resistance device with memory, (c) Switching device, (d) Switching device with memory, (e) Voltage controlled negative resistance device with memory.

Quite a few phthalocyanine derivatives have been reported to date with regard to the conductivity in forms of LB films [222-231], some of them aimed at constructing chemical sensors [207,232-234]. Voltage controlled negative resistance [235] as well as electro-chromism [236] have been reported. Porphyrines were also used for the construction of conductive LB films [237,238] and applied to porphyrin based gas sensors [239-241]. 

E > E (E less negative). The applied voltage is negative of Ej and as soon as B is produced at the electrode by the chemical reaction B is immediately reduced at a diffusion-controlled rate. This increases the observed height of peak A, for this wave now contains current from the reduction of B as well as from A. When the couple B/B is reversible, the wave for B can be seen if the reverse scan is sufficient to go positive of Eg. In a single CV scan, only the oxidation wave of B in the B/B couple will be seen, but if two successive triangular potentials are applied to the electrode, the full reversible wave of B will be observed (Fig. 2). 

The capacitive sensor transforms the pH variation to a capacitance change (AC). A differential cross-coupled voltage-controlled oscillator (VCO), as shown in Fig. 7.6, is implemented to convert the capacitive variations (AC) into frequency variation (AF). The differential cross-coupled VCO consists of negative transconductances as well as an inversion-MOS (I-MOS) varactor (Cq) [97] and inductor (Lq) acting as an LC-tank... 

The plasma source implantation system does not use the extraction and acceleration scheme found in traditional mass-analy2ing implanters, but rather the sample to be implanted is placed inside a plasma (Fig. 4). This ion implantation scheme evolved from work on controlled fusion devices. The sample is repetitively pulsed at high negative voltages (around 100 kV) to envelope the surface with a flux of energetic plasma ions. Because the plasma surrounds the sample, and because the ions are accelerated normal to the sample surface, plasma-source implantation occurs over the entire surface, thereby eliminating the need to manipulate nonplanar samples in front of the ion beam. In this article, ion implantation systems that implant all surfaces simultaneously are referred to as omnidirectional systems. 

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