Langmuir-Blodgett devices

One of the new trends in chemical analysis appeared in the last decade is that the miniaturization. It becomes apparent in the miniaturization of analytical devices, separation procedures, measuring tools, analyzing samples and as a consequent the term micro have appeared. Further development of this trend have led to transfer from the term micro to nano one (nanoparticles, nanofluides, nanoprobes, nanoelectrodes, nanotubes, nanoscale, nanobarcode, nanoelectrospray, nanoreactors, etc). Thereupon a nanoscale films produced by Langmuir-Blodgett (LB) technique are proposed for modifying of chemical sensors. 

Therefore, investigators have shown considerable interest in the adoption of the Langmuir-Blodgett technique, or its modifications, to make molecular electronic devices using, in particular, as an active component, a light-transducing protein, such as BR. In fact, the ability of BR to form thin films with excellent optical properties and the intrinsic properties themselves make it an outstanding candidate for use in optically coupled devices. 

M Era, C Adachi, T Tsutsui, and S Saito, Organic electroluminescent device with cyanine dye Langmuir-Blodgett film as an emitter, Thin Solid Films, 210/211 468-470, 1992. 

Xie R, Bryant GW, Zhao J et al (2003) Tailorable acceptor Cgo-nBn and donor Cgo-niNm pairs for molecular electronics. Phys Rev Lett 90 206602/1-206602/4 Metzger RM (2003) One-molecule-thick devices rectification of electrical current by three Langmuir-Blodgett monolayers. Synth Met 137 1499-1501... 

Three-methods have been pursued to organize monolayers from different organic compounds to form molecular monolayer FETs (1) thermal evaporation of approximately monolayer thickness on the dielectric surface of FETs, (2) Langmuir-Blodgett assembly on the water surface and transfer to device surfaces, and (3) self-assembly of functionalized organic compounds on the surface of the gate, or gate dielectric layers of FETs. 

The focus in this chapter is on the scientific issues and challenges in the application of vapor deposited top metal contacts to devices fabricated from self-assembled monolayers (SAMs) and related films such as Langmuir Blodgett (LB) monolayers. Specifically the chapter will review the types of possible interactions... 

The application of Langmuir-Blodgett films as rectifiers and/or switches have been also proposed. Peterson [106] investigated two semiconductors polyparaphenylene 178 and polyphenylenevinylene 179 with these purposes in mind. These systems with the chain lengths of at least 20 units could also be used as photovoltaic devices since their electroluminescence should be readily detectable. The doping of such materials may be necessary but at present it is not clear whether they will form Langmuir-Blodgett films when doped. 

FIG. 7.21 An optical switching device based on Langmuir-Blodgett films. (Redrawn with permission of P. Ball 1994.)... 

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