Increasing the optical modulation of low energy electron transmission by the deposition of copper phthalocyanine dye on Si(111)

Abstract

When films of copper phthalocyanine dye (CuPc) are deposited on etched Si(111) wafers, there is approximately an order of magnitude increase in the optically modulated transmission of low energy electrons. For comparison, the relatively small optically modulated currents obtained for CuPc films on metal contacts have also been measured. This increase in the optically modulated current due to the CuPc deposition occurs for both n- and p-type Si but does not occur when an intervening layer of insulating oxide is present at the Si-phthalocyanine interface. The dependence of this increase in the optically modulated current on both the incident photon and electron energy has been examined. The dependence on photon energy is consistent with photo-generation of electron hole pairs in Si while the complicated electron energy dependence indicates that electronic interactions with the phthalocyanine molecule are probably involved.