Langmuir-Blodgett devices semiconductor

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. 

However, the successful use of processes dependent on Langmuir-Blodgett films for semiconductor applications is in doubt due to the presence of water and other detrimental contaminants in the films produced. The internal dislocations required for switching by the molecules may not be facile since the molecules are expected to be packed into semicrystalline phases in the Langmuir-Blodgett films. In addition, new developments in the field may obviate the need for such films as part of the device. 

More recently, Fendler and coworkers have used surfactant vesicles as hosts for colloidal semiconductor particles [83]. For instance, dihexadecyl phosphate (DHP) and 2Ci8Br vesicles incorporating CdS, ZnS and mixed CdS-ZnS particles have been obtained and used for the realization of nanoscale photoelectric devices (see later). It is important to point out, however, that the presence of the closed vesicle does not appear, at least with these systems, to be of critical importance for the control of the size of the particles, as similar phenomena also occurs in Langmuir-Blodgett films [84], suggesting that a crucial role in nucleation is played mainly by the surface. 

High-resolution circuitry and active devices employing Langmuir-Blodgett film techniques or polymer-based transistors are being considered for the sophisticated electronics required in future vehicles. Temperature or energy balance in the vehicle could be controlled through conductive polymers or semiconductor deposits on electrochromic windows. Electroluminescent liquid crystals and fluorescent and electrochromic materials used for visual displays show promise for future development. 

Paloheimo et al. [208] described the function of a P(3-hexyl-T) based field effect transistor (FET), whose I-V characteristics are shown in Fie. 23-29. Tliey also described the use of this device as a sensor for such analytes as ammonia. Paloheimo et al. also described [1013] novel FETs based on mixed Langmuir-Blodgett films of P(3-hexyl-T) and arachidic acid. In these, film thicknesses were single monolayers to 35 monolayers (ca. 3.7 to 130 nm), and the undoped CP was the active semiconductor. The FET channel width and length were 8 cm and 5 pm respectively. The primary application envisioned was gas sensing. Like other organic-based FETs,... 

Industrial Applications Determining cationic surfactants electroluminescent devices Langmuir Blodgett films - photoresists semiconductor surfactant composite films ... 

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