Metal/insulator systems are being widely studied for the their use in the fields of catalysis, in devices such as organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs) devices, and in the emerging field of microelectronics. To date, however, little is known about the ultrafast behavior of electrons in these systems. Time- and angle- resolved two-photon photoemission is used to study the dynamics of the electronic states at the NaCl/Ag(100) interface. We observe the n=1, 2, and 3 image potential states. Electrons in the n=1 state undergo a trapping with a high probability, as shown by a dynamic change in their energy on the order of a few hundred meV. Momentum resolved measurements show that the n=1 state is initially delocalized, but becomes localized within a few hundred femtoseconds via decay through multiple distinct localized states. The localization is believed to occur at step edges of the NaCl islands. Our studies correlate coverage and temperature with the dynamics and magnitude of electron trapping in this state. In order to show the generality of these phenomena, we are extending our studies to the NaCl/Ag(111) interface and other films of other alkali halides such as KCl and NaF. We also aim to deposit organic semiconductor on the alkali halide spacer layer mimicking the junction found in real devices to gain insight on the electron dynamics.

Trapping of free electrons at the NaCl/Ag(100) interface

248th National Meeting (2014)

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