Interplay of the photon drag and the surface photogalvanic effects in the metal-semiconductor nanocomposite

G M Mikheev,A S Saushin,Yu P Svirko,V M Styapshin

doi:10.1038/s41598-018-26923-2

Abstract

Photon drag effect (PDE) and surface photogalvanic effect (SPGE) can be observed in centrosymmetric media and manifest themselves in photocurrents, the magnitude and polarity of which depend on wavevector and polarization of the excitation laser beam. PDE photocurrent originates from the transfer of the photon momentum to a free charge carrier, while SPGE photocurrent is due to diffuse scattering of the photoexcited carriers in the subsurface layer. However, despite the different underlying physical mechanisms, these photocurrents have almost indistinguishable dependencies on the polarization and the angle of incidence of the excitation laser beam. In this paper, we observe for the first time a competition between PDE and SPGE in the film containing metal (Ag-Pd) and semiconductor (PdO) nanocrystallites. We show that, depending on the angle of incidence, polarization azimuth and wavelength of the excitation laser beam, the interplay of the PDE and SPGE leads to the generation of either monopolar or bipolar nanosecond current pulses. The experiments performed allow us to visualize the contributions both these effects and obtain light-to-current conversion efficiency in a wide spectral range. Our experimental findings can be employed to control the magnitude and polarity of the light-induced current by polarization of the excitation laser beam.

Highlights

Photon drag effect (PDE)[1,2] and surface photogalvanic effect (SPGE)[3,4] manifest themselves as light-induced currents, magnitude and polarity of which depend on the wavevector and polarization of the excitation laser beam
In the visual and near-IR spectral range, the PDE is due to the transfer of the photon momentum to a charge carrier[1,2,19], while the SPGE originates from interband transitions in the subsurface layer that produce conduction electrons with anisotropic momentum distribution
The PDE and SPGE photocurrents, which are generated in the irradiated film, have opposite polarities

Summary

Introduction

Photon drag effect (PDE)[1,2] and surface photogalvanic effect (SPGE)[3,4] manifest themselves as light-induced currents, magnitude and polarity of which depend on the wavevector and polarization of the excitation laser beam. Having originated from very different mechanisms, SPGE and PDE show very similar dependences on the angle of incidence and polarization of the excitation beam[16,18,23] This makes separating them in metals[18] or semimetals[16,23] a difficult experimental task. Irradiation with intense laser pulses can give rise to the PDE photocurrent in metal constituent, while interband transitions in semiconductor nanoparticles should produce the SPGE photocurrent It is worth noting, that the nanocomposite should be centrosymmetric to avoid linear and circular photogalvanic effects[24,25,26] and should possess relatively low conductivity to suppress shot cut currents

Methods

Results

Conclusion