Dresden 2003 – scientific programme
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DS: Dünne Schichten
DS 24: Poster
DS 24.34: Poster
Tuesday, March 25, 2003, 14:30–17:00, P2a
Photoemission of Ag films induced by ultra-short pulse excitation — •A. Gloskovskii1, D.A. Valdaitsev1, M. Cinchetti1, S.A. Nepijko1,2, G. Schönhense1, L.V. Viduta2, J. Lange3, M. Bauer3, and M. Aeschlimann3 — 1University Mainz — 2Institute of Physics, Kiev, Ukraine — 3University Kaiserslautern
A wedge-shaped Ag film was prepared on a glass substrate in ultrahigh vacuum conditions. Its photoemission properties were studied. Its mass thickness varied from several tens (continuous film) down to several tenths of nanometers (island film). The exact mass thickness, sizes of islands and distances between them were measured by using transmission electron microscopy and atomic force microscopy. A Ti-sapphire laser with the fundamental wavelength λ=800 nm (pulse FWHM τ=50-300 fs, power P=500 mW) or with the first harmonic λ=400nm (τ=100 fs, P=100 mW) served as a source of excitation. The collecting voltage was sufficiently high to collect all emitted electrons. The performed measurements revealed a non-monotonous character of the dependence of the photoemission current intensity on the effective thickness of the Ag film under study. As the mass thickness decreases, the emission current first decreases slightly and then increases by several orders of magnitude. The maximum emissivity is reached at a mass thickness corresponding to several monolayers Ag. Towards lower thickness a strong drop in emissivity indicates the decrease of Ag cluster density. An increase of the laser pulse duration resulted in a sharp decrease of the emission current intensity. The obtained results can be explained by the electron gas heating in Ag clusters.