123rd General Meeting of the KCS

Type Oral Presentation
Area Oral Presentation of Young Inorganic Chemists
Room No. Room 401+402
Time THU 10:10-10:20
Code INOR.O-8
Subject Structure-Thermopower Relationships Achieved with Large-Area Thermoelectric Molecular Junctions
Authors Sohyun Park, Hyo Jae Yoon*
Department of Chemistry, Korea University, Korea
Abstract Studies of thermopower in molecular junctions permit access to the atomic-detailed energy topography across junctions and how thermopower is associated with chemical structure of the active molecular components inside junctions. In this presentation, we show liquid metal-based thermoelectric junction technique and structure-thermopower relationships established with the technique. Cone-shaped liquid Ga-In alloy (EgaIn) microelectrode allows us to achieve high yields of working junctions and thus statistically sufficient thermoelectric data sets. Using this new technique, we tested the dependence of thermopower on the length of molecules with and without π-electrons: that is, oligophenylene and n-alkane monothiolates chemisorbed on gold substrates. Our results reveal that the length dependence of thermopower predominantly depends on the presence and absence of π-conjugation. The change of Seebeck coefficient as a function of molecular length is opposite for the oligophenylene and n-alkane backbones : as the length of molecules increases, Seebeck coefficient increases and decreases for oligophenylene and n-alkane backbones, respectively. These findings are consistent with previous results in literature. More interestingly, thermoelectric junction measurements over n-alkane monothiolates indicate that the decrease rate of Seebeck coefficient changes at n-undecanethiolate (SC11) from -0.60 to -0.034. We discuss the origin of this observation based on metal-induced gap states (MIGS), which have been theoretically proposed (and not experimentally proven yet) in self-assembled monolayers on gold.
E-mail psh9491@naver.com