Pictures SFB616

 Project A3:
The Energy Dissipation of Cold Reactive Particles on Surfaces

 The aim of the project is the investigation of the energy dissipation of cold reactive particles on noble metal surfaces. The reactive particles are produced by means of a surface wave sustained plasma [1]. The dissipation mechanism is studied using thin film MIM detectors (metal-insulator-metal). These systems allow the detection of weak electronic surface excitations. The interaction of surfaces with ions and metastable atoms has been studied for a long time. The resulting exoelectron emission is well understood. However the measurement of weak electronic excitations in the interior of the metal is a new field. MIM detectors are promising tools for such studies as they allow the detection and spectroscopy of such internal excitations [2]. The figure below shows a simple sketch of a MIM detector.


simple detection

 We expect basic results concerning the understanding of plasma surface interactions which are relevant for the chemistry on metal surfaces. It consists of a 20 nm thick base Al-electrode, which is separated from the 20 nm thick noble metal top electrode by a 2 nm thick anodic oxide layer. The detection principle is illustrated by the neutralisation reaction of an Argon ion at the surface consisting of three steps:

1. Neutralisation of the ion releasing an excited defect electron at the surface.

2. Migration of the defect electron through the top electrode to the opposite interface.

3. Replenishing of the excited defect electron by means of the tunnel process with electrons from the aluminium base electrode. The application of a tunnel voltage between the two electrodes allows the energy sensitive modulation of step 3 and thereby the spectroscopy of the surface process.