The thermoelectric effect is the conversion of electrical to thermal energy and vice versa, and it is of great interest in energy harvesting, cooling mechanisms based on the Peltier effect, and photodetectors based on the Seebeck effect. In the photothermoelectric effect or PTE, photons are used to produce thermal energy and a temperature gradient, and then electrical energy. Previous studies show the unexpected localized variation in the Seebeck coefficient, and further efforts in the Natelson Lab have been directed to understanding these behaviors. In the first part of this thesis, studies of thermocouples with gold single crystals are introduced, to help us figure out the thermoelectric behavior of individual grains, to push us one step closer to solving the localized variation of Seebeck coefficient puzzle. Experimental and simulation results are being introduced.

Photodetectors based on photothermoelectric effect can be made, and this is the focus of the second part of this thesis. Asymmetric gold nanostructures can make localized optical absorption in the structure; combine that with Seebeck coefficient changes and the result will be an electrical signal when the whole geometry is illuminated. Geometries that can have plasmon resonances at desired wavelengths can be used to increase the absorption for that wavelength and so make the photodetector spectrally sensitive. Simulations and experiments are been discussed.