Self-Assembled Monolayer Gate Dielectrics

H. Klauk and U. Zschieschang. Low-Voltage, Low-Power Organic Complementary Circuits with Self-Assembled Monolayer Gate Dielectric. In Device Research Conference, 2006 64th, pages 213-214, 2006. 

Bottom-gate, top-contact (Fig. 4.2a) and a bottom-gate, bottom-contact (Fig. 4.2b) TFT configurations are used to evaluate the FET performance of our semiconductors. The devices are built on an n-doped silicon wafer (gate electrode) with a 100-nm thermal silicon oxide (SiC>2) dielectric layer which is modified with a self-assembled monolayer of octyltrichlorosilane (OTS-8) to promote molecular ordering in the semiconductor layer. For the top-contact device the semiconductor layer ( 20-50 nm) is deposited on the OTS-8-modified SiC>2 surface by spin coating. A... 

The device yield of TFTs with molecular gate dielectrics would be expected to be low, because of defects in the thin self-assembled monolayer arising from the imperfect surface of the evaporated aluminum bottom electrode. Results obtained on... 

The TFT fabrication process on glass substrates starts with 100 nm of Cr for the gate metal, and is followed by a PECVD 200 nm thick Si3N4 dielectric with a 30 nm thick SiC>2 surface layer. The source drain metal is Cr/Au. Each of these layers is patterned using printed wax masks and chemical etching, steps a to d in Fig. 11.8. The surface is modified with a solution deposition of a self-assembled monolayer of octyltrichlorosilane (OTS-8) before inkjet printing deposition of the semiconductor. It has been shown that the OTS-8 layer affects the structural order of PQT-12 in thin films, improving the performance of the TFT [23]. Encapsulation and possibly other subsequent layers may be needed on the TFT, but these are not discussed here. 

Park, Y.D., Kim, D.H., Jang, Y, Hwang, M., Lim, J.A. and Cho, K., Low-voltage polymer thin-fihn transistors with a self-assembled monolayer as the gate dielectric, Appl. Phys. Lett, 87, 243509, 2005. 

R. T. Weitz, U. Zschieschang, F. Effenberger, H. Klauk, M. Burghard, and K. Kern, High-performance carbon nanotube field effect transistors with a thin gate dielectric based on a self-assembled monolayer. Nano letters, 7 (2007) 22-27. 

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 hquid crystalline, a-substituted quinquethiophene was used by the same group to translate this approach of self-assembly from the Si02 gate dielectric surface of FETs to assembly on organic dielectric surfaces, a first step toward fabricating flexible monolayer electronics [72]. Figure 11a provides a schematic of... 

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