Photothermoelectric Effects in GoldNanostructures
Doctor of Philosophy
Nanostructures in noble metals(e.g Au,Ag) provide unique properties for emergingapplications. One of the most important and interesting properties is the plasmonicresponse, where the electron gas in the metal can couple with electromagnetic radia-tion of wavelengths that are far larger than the nanostructure size. As a result, thelocal electric field can be significantly enhanced. Due to this property, the nanostruc-tured metal device can be locally heated by an incident light, and cause electrons totravel through the device. By measuring the electronic transport and open circuitvoltage, the characteristics of this photothermoelectric effects can be well studied. Ifone can raster-scan the laser and probe the response of the device as a function ofthe laser position, the variation of photothermoelectric response along the nanostruc-tured device can be collected. In this dissertation, I mainly focused on the study ofphotothermoelectric effects in the gold nanowire. We observed that the photother-moelectric response varies when scanning across the gold nanowire with a focusedlaser beam. Such a phenomena can be possible caused by local Seebeck coefficientvariation. After annealing the device with relatively low temperature (200◦C), theoverall intensity of PTE response is significantly reduced. This result indicates that a major contribution to the local Seebeck coefficient is residual strain along the device.Moreover, we modified the surface of the gold nanowire with different methods and successfully ruled out some other factors, which can potentially cause this phenomena.
Photothermoelectric effects; Gold nanostructure; Plasmonic