Time-resolved current response of a nanosecond laser pulse illuminated STM tip |
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Authors: | J Jersch F Demming I Fedotov K Dickmann |
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Institution: | (1) Lasercenter FH Muenster (LFM), FB Physikalische Technik, D-48565 Steinfurt, Germany (Fax: +49-2551/962-490, E-mail: laserlab@fh-muenster.de), DE |
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Abstract: | Time-resolved dependence of the transient current through a ns laser pulse illuminated scanning tunneling microscope (STM)
tip/sample gap in tunneling mode and out of tunneling range is presented. A self-designed fast STM-preamplifier (bandwidth
35 MHz) allows one to resolve the fine structure of the transient signal as well as the observation of some effects that are
undetectable by using conventional low-band preamplifiers. The dependence of the threshold laser pulse intensity, which corresponds
to the beginning of electron emission from tip (in non-tunneling mode), as a function of the tip/sample distance was investigated.
At tip/sample distances from tunnel contact up to approximately 1 μm a linear dependence is found. This behavior is in good
agreement with the theory for field enhancement in a STM tip/sample system. In tunneling mode a ns (fast component) as well
as a μs (slow component) current response was found as a result of the laser pulse illumination. These data suggest the tip
bending to be an important factor in clarifying the thermal/mechanical mechanism of laser-assisted surface nanomodification.
Received: 4 May 1998 / Accepted: 29 January 1999 / Published online: 28 April 1999 |
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Keywords: | PACS: 61 16 P 65 70 79 20 Ds 42 60 K |
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