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DS: Fachverband Dünne Schichten

DS 45: Ion Interactions with Nano Scale Materials I (Focused Session -- Organisers: Diesing, Facsko)

DS 45.4: Talk

Thursday, March 17, 2011, 12:00–12:15, GER 37

Time resolved transport of alkali ions through ultra-thin films — •Susanne Schulze and Karl-Michael Weitzel — Philipps-Universität Marburg, Fachbereich Chemie, 35032 Marburg

In this study, we report on the transport of K⁺ through poly(para-xylylene) films of 200 to 3000 nm thickness. The experiments are performed in an ultra-high vacuum chamber where an ion beam is generated by thermionic emission of K⁺ from aluminosilicates [1]. In one experiment the film is bombarded by a c.w. K⁺ ion beam. Individual ions transmitted through the film are detected by two microchannel plates. The analysis of the pulse-pair correlation function of successive ion detection events reveals a sharp drop in the width of the probability distribution between impact energies of 1300 and 1400 V. This variation is interpreted as an indication of a change in the underlying transport mechanism connected to an electrical breakdown induced by space charge zones as a consequence of the ion bombardment [2]. In a second experiment the film is bombarded by a pulsed ion beam. Ions passing through the film are analysed in a time of flight (TOF) spectrometer. The TOF is measured through the film as a function of the impact energy and is compared to the one in the absence of the film. For low impact energies the ions are delayed by the film, which is not the case for high impact energies. These results will be discussed in terms of the transition from diffusive to space-charge driven transport. [1] T. Kolling, A. Schlemmer, C. Pietzonka, B. Harbrecht, J. Appl. Phys., 107, 014105, (2010). [2] K. Schröck, S. Schulze, A. Schlemmer, K.-M. Weitzel, J. Phys. D Appl. Phys., 43, 025501, (2010).