Transistor base electrode

More recently. Gamier and coworkers used a printing technique to make OFETs on polymeric substrates [61]. Although printable field-effect transistors based on inorganic semiconductors have been reported as early as 1967 ]62], they did not come to any commercial development. We note, however, that in Gar-nier s device only the electrodes were actually printed. 

Fig. 6. Molecular transistor based on a microelectrode array. P is a polymer layer that can be switched conductive or nonconductive by the potential of the gate electrode (from ref.

Figure 9. SET transistor, based on self-assembling of gold nanoclusters on electrodes fabricated by electron-beam epitaxy. (Reprinted with permission from Ref [26], 1997, American Institute of Physics.)...

D.S. Kim, H.J. Park, H.M. Jung, J.K. Shin, Y.T. Jeong, P. Choi, J.H. Lee, and G. Lim, Field-effect transistor-based biomolecular sensor employing a Pt reference electrode for the detection of deoxyribonucleic acid sequence. Jpn, J. Appl. Phys. 43, 3855-3859 (2004). 

Metal oxide semiconductor field-effect transistors (MOSFETs) are field effect transistors with a thin film of silicon dioxide between the gate electrode and the semiconductor. The charge on the silicon dioxide controls the size of the depletion zone in the polype semiconductor. MOSFETs are easier to mass produce and are used in integrated circuits and microprocessors for computers and in amplifiers for cassette players. Traditionally, transistors have been silicon based but a recent development is field-effect transistors based on organic materials. 

Fig. 2.19. (a) Scheme of a transparent field effect transistor based on ZnO [191]. The gate electrode consists of tin-doped indium oxide (ITO) and the gate dielectric is a multilayer of AECE/TiCE (ATO). (b) Output characteristics (drain-source current as a function of the drain-source voltage) for different gate voltages. The saturation current is about 530 rA at a gate bias of 40 V. From this output characteristics a threshold voltage of 19 V and a field-effect mobility of 27 cm2 V-1 s-1 were calculated [192]... 

Conductors are required in several areas in printed electronics. Conductors are used to form low-resistance interconnects, and antennae, as well as to form contact electrodes within transistors. Based on conductivity requirements, a range of conductors exist, ranging from flake inks (typically not inkjettable, and therefore not considered here), to nanoparticle inks and polymer conductors. 

Electroehemical transdueers are elassified as amperometric, potentiometric or conductometrie [8]. In addition we will here consider field-effect transistor-based transducers separately. Potentiometric sensors make use of the development of an electrical potential at the surface of an electrode when it is placed in a solution containing ions that can exchange with the surface. The potential of the electrode is... 

Although not an ion, glucose can be detected by virtue of an MIP-derived ion. The pH electrode is simply an ISE for H". Glass and ion-selective field effect transistors pH electrodes are the best characterised and the most successful ISEs. Many sensors employ chemical reactions to produce H" or OH ions and employ pH electrodes for signal transduction. An imprinted sensor based on this approach is the glucose sensor produced by Arnold s group [10]. This polymer employs a metal ion (Cu " ) in the imprinted site and makes use of the metal s... 

Fig. 13. Microelectrochemical device, (a) Schematic illustration of the microelectrochemical transistor based on polyaniline (thickness of the polyaniline layer 5 pm, electrode width 1-2 pm, distance 2-4 pm) (b) characteristic curve of the polyaniline transistor (Id versus Vg at Vd = 0.18 V). (Redrawn from Wrighton, 1986).

The direct fixation of the biocatalyst to the sensitive surface of the transducer permits the omission of the inactive semipermeable membranes. However, the advantages of the membrane technology are also lost, such as the specificity of permselective layers and the possibility of affecting the dynamic range by variation of the diffusion resistance. Furthermore, the membrane technology has proved to be useful for reloading reusable sensors with enzyme. In contrast, direct enzyme fixation is mainly suited to disposable sensors. This is especially valid for carbon-based electrodes, metal thin layer electrodes printed on ceramic supports, and mass-produced optoelectronic sensors. Field effect transistors may also be envisaged as basic elements of disposable biosensors. 

Bipolar junction transistors are based on an n-p-n or p-n-p junction sequence. One of the p-n junctions is reverse biased, which suppresses the current between the outer electrodes, commonly called emitter and collector. The middle layer, which is connected to a third electrode (base), is spatially very thin. Initiated by a small control current over the base electrode, charge carriers are injected over the forward biased p-n junction and minority carriers can flood directly over the reverse biased p-n junction. This causes an increased current between emitter and collector. In contrast to FETs, bipolar junction transistors are current controlled. 

Figure 11. SET transistor, based on 1,7-(CH3)2-1,2-C2BioH9T1(OCOCF3)2 carbor-ane molecules in a LB film on a gold electrode array deposited on graphite (HOPG). ...

CaMV35S 35S promoter from cauliflower mosaic virus CPE carbon paste electrode EIS electrochemical impedance spectroscopy GCE as carbon electrode PAT phosphinothricin acetyltransferase SNFETs field-effect transistors based on sin e-walled carbon nanotube networks. 

When Lee and Subramanian invented the first fibrous transistor (Lee and Subramanian, 2003), they did not use it to develop a textile circuit. The reason may be in the rigidity, stability, and reproductivity of the fibrous transistor. The wire was in aluminum. It was difficult to insert it into woven fabric as a normal textile filament. Moreover, its evaporated semiconductor and source-drain electrodes were delicate. They would be easily destroyed during the assembly process. Besides, the source-drain electrodes were only in one side of the wire. The alignment with other conductive yams was a problem in the source-drain position. Even if this kind of fibrous transistor was ameliorated by using stainless wire as gate and depositing the source-drain around the whole wire (Lee and Subramanian, 2005 Maccioni et al., 2006), there still was no laboratory prototype of a fibrous transistor-based electronic circuit published. Because the deposition should be carried out in vacuum, it became impossible to exploit series manufacturing for... 

Several sensor configurations are manufactured from randomly oriented CNTs, conductive CNT films, and CNT-coated electrode surfaces to transistor-based sensors. CNT films and composites are well suited for macro- and microscale sensing platforms, such as smart wearable fabrics and lab-on-chip devices, in which concentrations of analytes are above several micromolars. Smaller electrodes, with tips ranging from hundreds of nanometers to hundreds of micrometers, have been coated with CNTs to enhance their sensitivity. 

Bipolar transistors are realized using either an npn- or pnp-junction sequence. The different segments of the device are named as collector, base, and emitter electrode, respectively. In order to operate the transistor, one of the junctions is forward biased, while the other is biased in reverse. Using a small control current over the base electrode, a significant current between the collector and emitter electrodes is enabled. 

The increased interest in using ISEs has led to the development of new sensor materials that show high selectivity for a variety of anions and cations and new approaches for electrode constraction. Several attempts have been made to eliminate the internal reference electrode resulting in a solid-state sensor design. Examples of these types of sensors include coated wire electrodes, graphite rods, graphite-based electrodes, and ion-selective field-effect transistors (ISFETs). 

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