Single Metal Photodetectors Using Plasmonically-Active Asymmetric Gold Nanostructures.

Plasmonic-based photodetectors are receiving increased attention because simple structural changes can make the photodetectors spectrally sensitive. In this study, asymmetric gold nanostructures are used as simple structures for photodetection the photothermoelectric response. These single metal photodetectors use localized optical absorption from plasmon resonances of gold nanowires at desired wavelengths to generate temperature gradients.

Thermoelectric response from grain boundaries and lattice distortions in crystalline gold devices.

The electronic Seebeck response in a conductor involves the energy-dependent mean free path of the charge carriers and is affected by crystal structure, scattering from boundaries and defects, and strain. Previous photothermoelectric (PTE) studies have suggested that the thermoelectric properties of polycrystalline metal nanowires are related to grain structure, although direct evidence linking crystal microstructure to the PTE response is difficult to elucidate. Here, we show that room temperature scanning PTE measurements are sensitive probes that can detect subtle changes in the local Seebeck coefficient of gold tied to the underlying defects and strain that mediate crystal deformation.

Photothermoelectric Detection of Gold Oxide Nonthermal Decomposition.

A thin coating of gold oxide, metastable at room temperature, can be formed by placing gold in a strongly oxidizing environment such as an oxygen plasma. We report scanning photovoltage measurements of lithographically defined gold nanowires subsequent to oxygen plasma exposure. Photovoltages are detected during the first optical scan of the devices that are several times larger than those mapped on subsequent scans.

Substantial local variation of the Seebeck coefficient in gold nanowires.

Nanoscale structuring holds promise to improve the thermoelectric properties of materials for energy conversion and photodetection. We report a study of the spatial distribution of the photothermoelectric voltage in thin-film nanowire devices fabricated from a single metal. A focused laser beam is used to locally heat the metal nanostructure via a combination of direct absorption and excitation of a plasmon resonance in Au devices.