Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 12: Methods

O 12.1: Talk

Monday, March 27, 2006, 15:00–15:15, WIL B321

Near-field effects in heat transfer under UHV conditions — •Uli F.-Wischnath, Achim Kittel, and Andreas Knübel — Uni Oldenburg, Fak. V, C. v. Ossietzky Str., 26111 Oldenburg

The heat transfer between a sample and a probe in an STM based SThM (Scanning Thermal Microscope) is dominated by near field radiation when approaching to small seperations under UHV conditions. The nature of this evanescent part of the radiation is subject to ongoing discussions, especially the dependencies on temperature difference and distance.

We have measured the heat transfer between a gold-platin thermoelement as probe and different samples. The classical theory of fluctuating charge carriers predicts a strong increase when approaching the sample. This can be observed for seperations ranging from roughly 100 nm down to the order of one nanometer. For even smaller seperations a nearly constant value is found showing the breakdown of the classical theory.

We were able to trace the increase of the heat transfer above the far field value up to seperations of about 100 nm due to a new production process of the thermoelement. The more filigree new probe has its sensitive area about 100 times closer to the very end of the tip and has a ten times greater thermal resistance. This results in an increase in sensitivity by a factor of 15 compared to the ones used previously.