Influence of Material Structure on Thermoelectric Properties of Atomic Scale Systems
[electronic resource].

Description

Main Author

Balachandran, Janakiraman.

Related Names

University of Michigan. Library.

Language(s)

English

Published

2014.

Subjects

Nanoscale Thermoelectrics.
Ab-initio Modeling.
Electronic Transport.

Summary

these effects are complementary, resulting in a large total-shift towards lower energies. This mechanism and its influence was computationally demonstrated on various MMMJs. This mechanism provides a simple unified explanation of experimentally measured thermopower values in these heterojunctions. Finally, this mechanism also enabled us to develop very efficient computational strategies to compute the sign of the thermopower and in turn the nature of transport (p-type or n-type). This computational approach can potentially be used to analyze a very large set of MMMJs made from different molecules/metal systems to identify the heterojunctions with very high thermoelectric efficiency.
are an excellent test system to understand the electronic transport in nanoscale systems. In this dissertation, we develop ab-initio based computational models to quantitatively predict thermopower and injection barrier for numerous Au/aromatic molecule based MMMJs. Further, when a molecule is brought into contact with Au atoms, these computational models also enable us to understand the influence of molecular structure on the molecular energy level reorganization. Our analysis elucidates that the energy level reorganization depends on two dominant factors namely (i) the stabilization effect --- due to physical contact between the molecule and Au atoms, and (ii) the charge transfer effect --- due to chemical interactions between the molecule and Au atoms. In charge gaining molecules, these effects are competing with one another resulting in a small total-shift of the energy levels. However in case of charge losing molecules,
Developing high efficiency ambient temperature thermoelectric devices has huge potential in transforming electronics and biomedical industries. The efficiency of a thermoelectric device is quantified by its figure of merit ZT, which in turn is determined by material properties such as thermopower, electrical conductivity and thermal conductivity. One of the major challenges in improving the ZT values is the simultaneous maximization of thermopower and electrical conductivity ---which is possible only in zero dimensional nanoscale materials with discrete energy levels. To develop thermoelectric devices employing these nanoscale materials, we need to understand electronic transport in nanometer length scales. Heterojunctions where atomic-scale single molecules are placed in contact with metal electrode ---commonly referred as metal-molecule-metal heterojunctions (MMMJs)

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