Bidirectional Charge Transfer Research Articles

Impact of Bidirectional Charge Transfer and Molecular Distortions on the Electronic Structure of a Metal-Organic Interface

Interface energetics are of fundamental importance in organic and molecular electronics. By combining complementary experimental techniques and first-principles calculations, we resolve the complex interplay among several interfacial phenomena that collectively determine the electronic structure of the strong electron acceptor tetrafluoro-tetracyanoquinodimethane chemisorbed on copper. The combination of adsorption-induced geometric distortion of the molecules, metal-to-molecule charge transfer, and molecule-to-metal back transfer leads to a net increase of the metal work function.

Bidirectional charge transfer in repeated contacts to polymers

The contact charging of polymers by metals is thought to be a consequence of electron transfer; the direction of transfer appears to be influenced by the relative position of the fermi level of the metal and some energy level characteristic of the polymer [1,2]. What determines the amount of charge transfer is not definitely known at present; the question is complicated by the fact that repeated contacts (to a given place on the polymer surface) usually result in a gradually increasing charge (“charge accumulation”) [3–7], indicating that equilibrium may not be achieved in a single contact. In this note we report experiments which show that charge accumulation is not always monotonic: although the magnitude of the charge always increases on average, the charge transfer in any particular contact can be of either sign. We think this effect is important because it puts strong constraints on possible mechanisms of contact electrification (see below).