Charge transfer in metal/atactic polystyrene contacts

Contact charge-exchange experiments between various metals and atactic polystyrene are utilized to elucidate the electronic structure of the polystyrene. Bulk states present at approximately 1014/cm3 within a 4-μ-thick boundary layer, as well as surface states of approximate density 1010/cm2, govern the charge-exchange characteristics of polystyrene in the metal contacts. It is argued that the carriers are electrons injected from the region of the Fermi level of the metal into the polymer, and that the metal/polymer junction remains indefinitely in a nonequilibrium state. A steady-state injection level is reached because of differences in injection and transport properties of the surface boundary layer and the deeper bulk material. A significant effect of the substrate metal on the populations of the electronic states at the free surface of the polystyrene films is identified and shown to be long range (at least 15 μ).