CP-BASED MOLECULAR ELECTRONIC DEVICES

The Wrighton group at MIT, and other groups independently, noted that if conventional microelectronic fabrication techniques, which in the mid-1980 s were just broaching the fabrication of sub-micron scale, could be combined with the new CP technology, to yield CP microelectrodes . A number of these electrodes could be fabricated in the form of circuit elements, e.g. three electrodes as a transistor. If 

Wrighton group. After Reference [1012], reproduced with permission. 

Use of the device shown in Fie. 23-27 as an oxygen sensor. After Reference [395], reproduced with permission. 

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, 

Schematic diagram for a poly(acetylene) MISFET structure. Dimensions shown are to scale, except the channel width (20 pm) and length (1.5 m). After Reference [1014], reproduced with permission. 

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All books, reviews, and entries on CPs describe the potential applications. Chandrasekhar and others ° have reviewed in comprehensive fashion the applications of CPs, including batteries sensors electro-optic and optical devices microwave- and conductivity-based technologies electrochromic devices electrochemomechanical and chemomechanical devices corrosion protection semiconductor, lithography, and electrically related applications— photovoltaics, heterojunction, and photoelectrochemical cells capacitors electrolytic and electroless metal plating CP-based molecular electronic devices catalysis and delivery of drugs and chemicals membranes and LEDs. 

Describe the construction and function of one device referred to in Problem 8-specifically a FET based on P(T) or P(ANi). What are the performance limitations preventing the replacement of inorganic-semiconductor based microelectronic devices by those based on CPs, and the implementation of a true CP-based "molecular electronic device" technology Are any of these limitations of a fundamental chemical or physical nature and thus not likely to be overcome ... 

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