A microelectrochemical diode with submicron contact spacing based on the connection of two microelectrodes using dissimilar redox polymers

Closely spaced, 0.2-1 micrometer, Au microelectrodes on Si3N4 can be functionalized with polyvinylferrocene, PVFc(+)/(o), or with an N, N'- dibenzyl-4,4'-bipyridinium-based polymer, (BPQ(2+)/(+)n, derived from hydrolysis of N, N'-bis((P-trimethoxysilyl) benzyl)-4-4'bipyridinium, I. Two or eight-microelectrodes arrays can be connected with either polymer in the sense that net current can pass from one microelectrode to another, through the polymer, when one electrode is held at a potential where the polymer is oxidized and the other electrode is held at a potential where the polymer is reduced. From such steady state current an estimate of the diffusion coefficient for charge transport, DCT, in the polymer can be made; values in the range .000000001- 10 to the --10 power sq cm/s are found and accord well with earlier measurements of DCT for the polymers studies. A two-terminal diode can be fabricated by coating one electrode with (BPQ(2+)/(+))n and an adjacent electrode with PVFc(+)/(o) such that there is a connection between the microelectrodes via the (BPQ(2+)/(+)n/PVFc(+)/(o) contact. Current passes when the applied potential is such that negative lead is attached to the PVFc(2+)/(+)n-coated electrode and the positive lead is attached to the PVFc(;)/(o)-coated electrode. The switching time of a microelectrochemical diode is controlled by the time required to oxidize and reduce the polymers.