See poster on the glass wall of FLUX 2.103, AND master project information Borrel March 27th 2018, Van der Waals, 16:30-19:00
Thermoelectricity offers the possibility to convert heat directly into electricity without the need of moving parts. It has been mainly used in deep space missions, where solar energy is not an option, but a recent convergence of climate change, increasing energy demand, and nanotechnology have sparked a renewed interest in thermoelectricity. A good thermoelectric material has a high electrical conductivity and low thermal conductivity, which are contradicting statements in most macroscopic materials. Nanowires are predicted to be more efficient thermoelectric materials because it is possible to partially decouple these mechanisms. At AND we investigate the Thermo-Electric properties of nanowires and the possibility to make thermoelectric devices based on nanowires.
We have vacancies for Master's thesis projects in the following subjects:
The efficiency of a thermoelectric material is characterized by the figure of merit zT which is defined as:
zT=(α^2 σ)/κ T
Where T is temperature, α is the Seebeck coefficient, σ the electrical conductivity and κ the thermal conductivity. This project consists of measuring the electrical conductivity and Seebeck coefficient of InSb nanowires from cryogenic temperatures to 400K. Nanowires are to be transferred to a measurement platform, where ohmic contacts will be prepared by electron beam lithography. A measurement technique is to be developed in LabView to measure nanowires of various diameters varying from a few tenths of nanomeres of about a hundred nanometers.
The integration of nanowires into thermoelectric devices has remained a difficult challenge. However recent advances in nanowire growth have paved the way to initiate investigations on device fabrication. This project consists of ground breaking processing technology to develop a thermoelectric device based on InSb nanowire arrays. The goal of this project is to demonstrate that a nanowire-based device can be fabricated by applying technologies used in solar cells to develop a top electrical contact.
Phonons are lattice vibrations and they carry heat in the same way that electrons carry charge. Phonons in GaP have a mean free path in the order of few hundred of nanometers. When GaP nanowires are thing enough, ballistic heat transport may occur, which means that phonons travel greater distances, in the order of micrometers without scattering. This project consists of measuring the thermal conductivity of thin GaP nanowires to confirm unequivocally that these exciting new physics take place in nanowires.