Photothermoelectric Detection of Gold Oxide Nonthermal Decomposition

Abstract

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. The first-scan enhanced photovoltage correlates with a reduction of the electrical resistance of the nanostructure back to preoxygen-exposure levels. Repeating oxygen plasma exposure "reinitializes" the devices. These combined photovoltage and transport measurements imply that the enhanced photovoltage results from the photothermoelectric response of a junction between Au and oxidized Au, with an optically driven decomposition of the oxide. Comparisons with the known temperature-dependent kinetics of AuOx decomposition suggest that the light-driven decomposition is not a purely thermal effect. These experiments demonstrate that combined optical and electronic measurements can provide a window on surface-sensitive photochemical processes.

Remote Excitation of Hot Electrons via Propagating Surface Plasmons

“…This experimental approach is discussed in previous publications. 23,25,41 In a one-dimensional model, the OCPV of a device of length l, with both ends kept at a constant, uniform temperature, while the laser heats the device somewhere in the middle, is =…”

“…The optical chopper time scale (milliseconds) is far longer than the thermal equilibration time scale of the metal nanostructure, so that the measured response is essentially the thermal steady state. This experimental approach is discussed in previous publications. ,, In a one-dimensional model, the OCPV of a device of length l , with both ends kept at a constant, uniform temperature, while the laser heats the device somewhere in the middle, is , where x is the distance along the device, S ( x,T ) is the Seebeck coefficient of the material, which is both temperature- and position-dependent, and T ( x ) is the local temperature. Unless otherwise indicated, measurements were taken with the substrate in vacuum (<1 × 10 –5 mB) and at room temperature (∼298 K).…”

Evaluating the ratio of electron and hole mobilities from a single bulk sample using Photo-Seebeck effect

“…As important as these works are, they lack adequate analysis and interpretation of results, no practical application was demonstrated either. In recent years, the term "photothermoelectric effect" is often used in literature for a related yet different phenomenon: the detection of photocurrent under localized illumination on devices made of graphene [15,16] or other low dimensional materials [17][18][19][20], where the temperature gradients were generated by focused light beams. This is not to be confused with effects discussed here.…”

Single Metal Photodetectors Using Plasmonically-Active Asymmetric Gold Nanostructures

“…As a result, it is possible to make thermocouples with a single conductor. 8−11 Other factors that can tune the Seebeck coefficient include surface chemistry, 12 impurity concentration, 13 strain, 14,15 and modifications to band structure. Photodetectors based on PTE do not require external bias, so their intrinsic noise source is mainly Johnson−Nyquist thermal noise.…”

“…When the conductor dimensions are comparable to the mean free path of carriers, the electrical conductivity and thus S can be manipulated by engineering the geometry. As a result, it is possible to make thermocouples with a single conductor. − Other factors that can tune the Seebeck coefficient include surface chemistry, impurity concentration, strain, , and modifications to band structure.…”