Dresden 2011 – scientific programme
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DS: Fachverband Dünne Schichten
DS 7: Layer Properties: Electrical, Optical and Mechanical Properties
DS 7.4: Talk
Monday, March 14, 2011, 18:30–18:45, GER 37
Charging of internal interfaces in metal-insulator-metal heterosystems by low energy electron beams — •Johannes Hopster1, Marika Schleberger1, Andreas Wucher1, and Detlef Diesing2 — 1Fakultät für Experimentalphysik, Universität Duisburg-Essen — 2Fakultät für Physikalische Chemie, Universität Duisburg-Essen
Metal-insulator-metal (MIM) and metal-semiconductor (MS) heterosystems can be used to detect low energy electrons, which are for example released by a surface chemical reaction. These electrons usually do not have sufficient excess energy to overcome the work function of the metal film. But these electrons can overcome the internal barrier of the heterosystems since the internal barrier is usually 1-2 eV lower than the workfunction of the metal film. The transmission of electrons over the internal barrier is determined by its height and thickness. By exposing these heterosystems to a low energy electron beam in ultra high vacuum we studied the electron transmission. The barrier properties and the transmission of the device remain unchanged for small currents impinging on the device (< 1 nA). For primary electron currents > 100 nA the internal barrier can be reversibly changed. The barrier returns to its ground level state within some 10s following an exponential time law. The time constant depends clearly on the field strength in the device. A model considering charge exchange processes between the two interfaces of the device is presented to explain the beam induced barrier changes.