Tetrathiafulvalene-based conducting deposits on silicon substrates

Tetrathiafulvalene-based molecular conductors, namely [TTF][TCNQ], (TTF)(6)[N(C2H5)(4)](HPM12O40) (M = W, Mo), and TTF[Ni(dmit)(2)](2) have been processed as thin films on microrough (001)-oriented silicon substrates using three different techniques. CVD-grown [TTF][TCNQ] deposits consist of platelets (10 6 5 mm) and filaments (diameter similar to1 mum). CN stretching modes in the infrared spectrum and CC stretching modes in the Raman spectrum are in agreement with a charge transfer of similar to0.6 from the TTF donor to the TCNQ acceptor. The N(1s) photoelectron spectrum confirms the presence of a reduced tetracyanoquinodimethane moiety. The films exhibit a semiconducting behaviour with a room-temperature conductivity of similar to0.4 S cm(-1). Deposits of (TTF)(6)[N(C2H5)(4)](HPW12O40) are electrodeposited on microrough Si( 001) at constant current from TTF and [N(C2H5)(4)](3)(PW12O40) in acetonitrile solution. The films are made of stacked sheets (5 < thickness < 25 mum). Vibrational spectra, conductivity measurements and magnetic susceptibility data are similar to those obtained on single crystals of (TTF)(6)[N(C2H5)(4)](HPW12O40) grown on a platinum electrode. Thin films of TTF[Ni(dmit)(2)](2) are grown on microrough Si(001) by an adsorption process in organic solution. The deposits are characterized by Raman micro-probe and exhibit a pseudo-metallic behaviour with a room-temperature conductivity of about 2 S cm(-1).