Charge-flow transistor

Sensing chemical species is a much more difficult task than the measurement of mechanical variables such as pressure, temperature, and flow, because in addition to requirements of accuracy, stability, and sensitivity, there is the requirement of specificity. In the search for chemically-specific interactions that an serve as the basis for a chemical sensor, investigators should be aware of a variety of possible sensor structures and transduction principles. This paper adresses one such structure, the charge-flow transistor, and its associated transductive principle, measurement of electrical surface impedance. The basic device and measurement are explained, and are then illustrated with data from moisture sensors based on thin films of hydrated aluminum oxide. Application of the technique to other sensing problems is discussed. 

Aluminum oxide charge-flow transistor, transfer function, 171,173,174f Aluminum oxide moisture sensor aging effects, 174f charge-flow transistor, 172f hysteresis effects, 175f... 

Xie D., Jiang Y, Pan W., and Li Y, A novel microsensor fabricated with charge-flow transistor and a Langmuir-Blodgett organic semiconductor film. Thin Solid Films, 424, 247-252, 2003. 

Synthetic efforts focus on the molecular engineering of sensitisers that enhance charge separation at the oxide solution interface. The structural features of the dye should match the requirements for current rectification by analogy to the photofield effect in transistors, the gate for unidirectional electron flow from the electrolyte through the junction and into the oxide is opened by the photoexcitation of the sensitiser. The reverse charge flow, i.e. recapture of the electron by the electrolyte, could be impaired by judicious design of the sensitiser. The latter should form a... 

The control of charge flow by an electric quantity is a key issue of today s electronics. The concept to electrically specify the conductivity of a resistor by pure solid state effects was already proposed in 1928 by Julius Edgar Lilien-feld in Germany [1], The basic idea was to control the charge carrier density in a solid by an electric field, applied over a third electrode. However, there is no evidence for a practical realisation by Lilienfeld. The first report about a pure electrically controllable solid state device was the well know Germanium transistor from William Shockley, John Bardeen and Walter Brattain [2]. The new term transistor was later explained as a combination of the words transconductance and varistor . Meanwhile a broad variety of different transistor concepts exists, which, however, can be mainly subdivided in two basic operational principles ... 

The electronic circuits themselves would be composed of molecules that would individually act as wires, diodes, transistors, and memory devices. Conducting pol3aners would likely be used (60a) in many of these components. The polymers can be modified to give them memory states which can act by change of conformation or charge flow. A memory device could be addressed by current flow through the polymer, stimulated by an externally applied electric field, or by laser signal, etc. 

Solid-state electronic devices such as diodes, transistors, and integrated circuits contain p-n junctions in which a p-type semiconductor is in contact with an n-type semiconductor (Fig. 3.47). The structure of a p-n junction allows an electric current to flow in only one direction. When the electrode attached to the p-type semiconductor has a negative charge, the holes in the p-type semiconductor are attracted to it, the electrons in the n-type semiconductor are attracted to the other (positive) electrode, and current does not flow. When the polarity is reversed, with the negative electrode attached to the n-type semiconductor, electrons flow from the n-type semiconductor through the p-type semiconductor toward the positive electrode. 

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