University of Twente Student Theses


Interaction of TEMPO-derivative 2D spin systems with conduction electrons in thin gold films

Tijssen, Peter (2010) Interaction of TEMPO-derivative 2D spin systems with conduction electrons in thin gold films.

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Abstract:This report describes the investigation of 2D spin systems, made of a thin gold films covered with monolayers of organic molecules, which contain an unpaired spin. The idea behind these systems is that the unpaired electrons in the organic molecules interact with the conduction electrons inside the gold film underneath. This interaction gives rise to many spin phenomena which are interesting from a fundamental point of view and therefore ask for investigation. The systems investigated in this report consist of gold films with thicknesses of 5 and 10 nm and monolayers of two different molecules, which are derived from a 2,2,6,6-Tetramethylpiperidin-1-oxyl (TEMPO). This molecule contains an electronwith unpaired spin and if this electron is able to leave this molecule and hop to the gold and is replaced by another electron from the gold, it should give rise to the Kondo effect. Two other effects that will be investigated with these systems are weak localization and RKKY interaction. These three phenomena should be macroscopically observable through resistance changes at temperatures near zero K. Two different versions of these TEMPO-derivative molecules were synthesized. A longer one (with a 5-carbon alkyl chain) and a shorter one (without the 5-carbon alkyl chain). Theoretically, a longer linker molecule should lead to a lower Kondo temperature. We could only find presumptive evidence of the interaction between the localized and conduction electrons. Unfortunately no significant evidence was obtained, only minor changes in the resistance at temperatures below 10 K were observed. Therefore it can be concluded that the systems investigated here can not serve as 2D spin systems for future use in the "2D organic spin systems" project. It is therefore recommended to search for other molecules which do show significant effects
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Nanotechnology MSc (60028)
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