Field-effect transistors, function

Selenium and selenium compounds are also used in electroless nickel-plating baths, delayed-action blasting caps, lithium batteries, xeroradiography, cyanine- and noncyanine-type dyes, thin-film field effect transistors (FET), thin-film lasers, and fire-resistant functional fluids in aeronautics (see... 

Maehashi et al. (2007) used pyrene adsorption to make carbon nanotubes labeled with DNA aptamers and incorporated them into a field effect transistor constructed to produce a label-free biosensor. The biosensor could measure the concentration of IgE in samples down to 250 pM, as the antibody molecules bound to the aptamers on the nanotubes. Felekis and Tagmatarchis (2005) used a positively charged pyrene compound to prepare water-soluble SWNTs and then electrostatically adsorb porphyrin rings to study electron transfer interactions. Pyrene derivatives also have been used successfully to add a chromophore to carbon nanotubes using covalent coupling to an oxidized SWNT (Alvaro et al., 2004). In this case, the pyrene ring structure was not used to adsorb directly to the nanotube surface, but a side-chain functional group was used to link it covalently to modified SWNTs. 

Field effect transistors are miniature, solid-state, potentiometric transducers (Figure 4.22) which can be readily mass produced. This makes them ideal for use as components in inexpensive, disposable biosensors and various types are being developed. The function of these semiconductor devices is based on the fact that when an ion is absorbed at the surface of the gate insulator (oxide) a corresponding charge will add at the semiconductor... 

Polythiophenes (PTs)/CNTs composites have emerged as an intriguing system for use as photovoltaic devices and field effect transistors [57]. Swager and Bao independently reported methods for the assembling of PTs/CNTs systems and showed their great potential as transparent conductive films [58]. Another interesting application arises from the possibility to functionalize the polythiophene backbone for applications as chemical sensors [134]. 

Fig. 20 Charge carrier mobility in P3HT as a function of the charge carrier concentration. Squares refer to an experiment performed on a field effect transistor while circles refer to experiments done on an electrochemically doped sample. In the latter case the mobility is inferred from the steady state current at a given doping level. Solid and dashed lines have been fitted using the theory of [101]. The fit parameters are the site separation a, the prefactor Vq in the Miller-Abrahams-type hopping rate, the inverse wavefunction decay parameter y and the dielectric constant e. From [101] with permission. Copyright (2005) by the American Institute of Physics...

Liu S, Shen Q, Cao Y et al (2010) Chemical functionalization of single-walled carbon nanotube field-effect transistors as switches and sensors. Coord Chem Rev 254 1101-1116... 

Payne MM, Parkin SR, Anthony JE, Kuo CC, Jackson TN (2005) Organic field-effect transistors from solution-deposited functionalized acenes with mobilities as high as 1 cm2/ V-s. J Am Chem Soc 127 4986 987... 

A main focus of preparing metal dithiolenes functionalized with thiophene units has been for their incorporation into conjugated organic materials. On first glance, it would seem that the combination of metal dithiolenes and conjugated polymers could produce attractive new materials for use in such applications as field effect transistors and NIR optical materials. However, several challenges remain before these materials can be applied to useful... 

Fig. 38. Hall resistance Rnall of an insulated gate (ln.Mn)As field-effect transistor at 22.5 K as a function of the magnetic field for three different gate voltages. /tnaii s proportional to the magnetization of the (In.Mn)As channel. Upper right inset shows the temperature dependence of / Hall- Let inset shows schematically the gate voltage control of the hole concentration and the conesponding change of the magnetic phase (Ohno et al. 2000).

A. B. Kharitonov, A. N. Shipway, and I. Willner, An Au Nanoparticle/ Bisbipyridinium Cyclophane-Functionalized Ion-Sensitive Field-Effect Transistor for the Sensing of Adrenaline, Anal. Chem. 15199, 71, 5441. 

This list can be divided into three main classes based mainly on function and redox state. First, applications that utilize the conjugated polymer in its neutral state are often based around their semi-conducting properties, as in electronic devices such as field effect transistors or as the active materials in electroluminescent devices. Secondly, the conducting forms of the polymers can be used for electron transport, electrostatic charge dissipation, and as EMI-shielding mate-... 

The meso-functionalized bis(thien-2-yl)methanes 267 (X=S) and bis(furan-2-yl)methanes 267 (X=0) were used for synthesizing the first neutral meso-functionalized tetrathia[22]annulene derivatives 271 (X=S) and tetraoxa[22]annulene derivatives 271 (X=0) (Scheme 105). The compounds were tested for organic field effect transistor (OFET) studies and have shown good mobilities with p-type semiconductor behavior (11JCS(CC)905,12JCS(CC)121). 

The incorporation of siloles in polymers is of interest and importance in chemistry and functionalities. Some optoelectronic properties, impossible to obtain in silole small molecules, may be realized with silole-containing polymers (SCPs). The first synthesis of SCPs was reported in 1992.21 Since then, different types of SCPs, such as main chain type 7r-conjugated SCPs catenated through the aromatic carbon of a silole, main chain type cr-conjugated SCPs catenated through the silicon atom of a silole, SCPs with silole pendants, and hyperbranched or dendritic SCPs (Fig. 2), have been synthesized.10 In this chapter, the functionalities of SCPs, such as band gap, photoluminescence, electroluminescence, bulk-heterojunction solar cells, field effect transistors, aggregation-induced emission, chemosensors, conductivity, and optical limiting, are summarized. 

We recently succeeded in using the functional bionic component, PSI, for photonic devices using molecular-level assembly. Two topics are introduced in this section. The first concerns a biophotosensor in which PSI is directly coupled with an artificial electronic device (a field-effect transistor FET) via a molecular wire designed at the molecular level (Fig. 14). The second is a biophotoelectrode composed of PSI, ITO, and a molecular wire. 

This volume of the series focuses on the photochemistry and photophysics of metal-containing polymers. Metals imbedded within macromolecular protein matrices form the basis for the photosynthesis of plants. Metal-polymer complexes form the basis for many revolutionary advances occurring now. The contributors to many of these advances are authors of chapters in this volume. Application areas covered in this volume include nonlinear optical materials, solar cells, light-emitting diodes, photovoltaic cells, field-effect transistors, chemosensing devices, and biosensing devices. At the heart of each of these applications are metal atoms that allow the assembly to function as required. The use of boron-containing polymers in various electronic applications was described in Volume 8 of this series. 

Yanagi, H., Araki, Y., Ohara, T., Hotta, S., Ichikawa, M. andTaniguchi, Y. (2003) Comparative carrier transport characteristics on organic field-effect transistors with vapor deposited thin films and epitaxially grown crystals of biphenyl-capped thiophene oligomers. Advanced Functional Materials, 13, 767-73. 

Mode 2 devices which rely on a different detection principle are the Kelvin probe sensor and the CHEMFET. In the first case, a vibrating capacitor measures the change of the work function (see Figure 2), while in the second case the interaction is detected in the field-effect transistor mode.29 31... 

While the discussion in this chapter has focused on molecular layers on single crystal silicon surfaces, the attachment chemistries discussed here could easily be applied to functionalize silicon nanowires or nanoparticles. Silicon nanowires have been shown to exhibit interesting electrical transport characteristics and have been used to fabricate nanoscale pn junctions [95], field effect transistors [96] and biochemical sensors [97-100]. However, all these interesting phenomena have been reported on oxidized silicon nanowires. It is likely that better control over the surface properties, as could be achieved by employing some of the chemistry discussed here, could significantly improve the performance of these nanowire-based devices. From another perspective, silicon nanowires could prove extremely... 

A field effect transistor (FET) measures the conductance of a semiconductor as a function of an electrical field perpendicular to the gate oxide surface (13). When the gate oxide contacts an aqueous solution a change of pH will change the SiOj surface potential p. A site-dissociation model describes the signal transduction, a function of the state of ionization of the amphoteric surface SiOH groups (14). Typical pH responses measured with SiO ISFETs are 37-40 mV/pH unit (15). 

Functionalization of pentacene with the specific aim of improving performance in devices is a recent endeavor - the first use of a functionalized pentacene in a field-effect transistor was reported only recently (2003) [26], Functionalization of pentacene has led to the ability to engineer the solid-state arrangement, electronic, and solubility properties of this important semiconductor and to improve its stability and film-forming ability. Recent functionalized pentacene materials have yielded devices with properties comparable with those of the parent acene, have enabled the formation of devices from solution-deposited films, and have even changed the semiconductor behavior of this organic molecule from p-type to n-type. As functionalization strategies are refined, materials with all of the properties necessary for commercial device applications should soon be developed. 

---