A. S. Saushin

Circular photogalvanic effect observed in silver-palladium film resistors

The surface circular photogalvanic effect (CPGE) at a laser wavelength of 1064 nm was observed for the first time in silver-palladium resistors fabricated by a thick-film technology. The CPGE response was detected using the electrodes oriented parallel to the radiation incidence plane, for the laser beam obliquely incident onto the sample surface. The coefficient of the pulsed laser radiation power conversion into light-induced emf (with the polarity depending on the sign of the circular polarization) amounted to about 80 mV/MW for film dimensions of 0.02 × 20 × 20 mm and a load resistance of 50 Ω. The maximum absolute value of the conversion coefficient was observed for the angles of light incidence of ±60°.

Effect of the burning temperature on the phase composition, photovoltaic response, and electrical properties of Ag/Pd resistive films

Silver-palladium (Ag/Pd) films were grown by thick-film technology using a resistive paste consisting of Pd, Ag2O, and glass on ceramic substrates at burning temperatures of 878, 1013, and 1113 K. The effect of the burning temperature and Pd content in the initial paste on the phase composition, resistivity, photovoltaic properties of films, free carrier concentration, and mobility was studied. It was found that the films grown at a burning temperature of 878 K have the greatest factor of conversion of the pulsed laser power to the photovoltaic signal, which depends on the direction of the incident radiation wave vector. Using X-ray diffraction, X-ray photoelectron spectroscopy, and thermodynamic modeling, it was shown that the AgPd alloy and PdO oxide are the main components of the Ag/Pd film with photovoltaic properties.

Spectral dependence of circular photocurrent in silver-palladium resistive films

The exposure of silver-palladium (Ag-Pd) resistive films to obliquely incident nanosecond pulsed laser radiation with wavelengths of 1064, 532, 354.7, and 266 nm leads to the appearance of a photo-current dependent on the sign of the circular polarization of incident radiation (circular photocurrent). The photocurrent was determined by measuring pulsed photo-emf in a longitudinal geometry for which the plane of laser-radiation incidence onto the film was parallel to the electrodes. It is established that the response signal changes its sign with that of the angle of incidence, significantly decreases with the laser-radiation frequency, and consists of linear and circular contributions. The ratio of the circular to linear signal components significantly decreases with decreasing radiation wavelength. The obtained results can be used for the creation and development of a device capable of determining the sign of polarization of laser radiation.

Photon-drag in single-walled carbon nanotube and silver-palladium films: The effect of polarization

Abstract. Polarization influence on the photovoltaic current raised due to the photon-drag effect in the single-walled carbon nanotube (SWNT) films and nanostructured silver-palladium (Ag/Pd) resistive films is examined at the wavelengths of 532 and 1064 nm of nanosecond laser pulses. The SWNT films were synthesized by the aerosol chemical vapor deposition technique. Ag/Pd films, consisting of AgPd alloy and palladium oxide (PdO), were prepared by burning a special paste on a ceramic substrate. The films obtained were characterized by Raman spectroscopy. It is shown that the Ag/Pd films Raman spectra consist of PdO peak that moves from 650  cm−1 to 628  cm−1 as the excitation He-Ne laser power increases. The photocurrent was measured at the oblique incidence of the laser beam on the film in the direction perpendicular to the plane of incidence. It is found that the transverse photocurrent in the SWNT films at circular polarization is absent and does not depend on the direction of the electric field vector rotation (the sign of the circular polarization) of the incident irradiation. The photocurrent in the Ag/Pd films at circular polarized irradiation is significant and depends on the circular polarization sign. The results obtained demonstrate the potential applications of the Ag/Pd resistive films as a sensor of the circular polarization sign of the incident light pulse in a wide wavelength range.

The influence of PdO content on circular photocurrent in resistive Ag/Pd films

We have studied the influence of PdO content in resistive Ag/Pd films (consisting of this oxide and Ag–Pd solid solution) on photocurrent dependent on the sign of circular polarization of the exciting radiation. The photocurrent was excited by nanosecond pulsed laser radiation with a 532 nm wavelength and measured in the direction perpendicular to the plane of laser beam incidence onto the film. The content of PdO in the film was varied by electrolytic reduction of Pd from PdO in sulfuric acid solution. Raman spectroscopy and X-ray diffraction measurements showed that reduced PdO content in the film leads to nonlinear decrease in the magnitude of photocurrent. It is established that photocurrent is also observed when PdO is fully absent on the film surface. The obtained results suggest that the nature of photocurrent in Ag/Pd films is related to the structure of Ag–Pd solid solution.

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

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.

Direct measurement of the circular photocurrent in the Ag/Pd nanocomposites

Abstract. An experimental approach for the direct measurement of the circular photocurrent (CPC) has been developed. The method was tested for the measuring the CPC due to photon drag effect in the Ag/Pd nanocomposites film in a wide spectral range. Measurements were performed at the wavelengths of 266, 532, and 1064 nm. The experimental results were compared with those obtained by the indirect conventional scheme. The obtained results open a new possibility of application of the Ag/Pd nanocomposites film to determine the direction of the electric field vector rotation of elliptically polarized light.

Circular photocurrent in Ag/Pd resistive films upon excitation by femtosecond laser pulses

This paper presents the results of the experimental investigation of the generation of nanosecond photocurrent pulses in silver–palladium (Ag/Pd) resistive films under excitation by laser pulses with a duration of 120 fs at a wavelength of 795 nm. The photocurrent was detected in the direction perpendicular to the plane of incidence of the laser beam on the film. The 20-μm-thick films under investigation were a porous polycrystalline material consisting predominantly of nanocrystallites of the palladium oxide PdO and the Ag–Pd solid solution. The direction of the photocurrent observed in the films depends on the sign of the circular polarization of the incident radiation. It was found that the observed photocurrent depends on the angle of incidence in accordance with the odd law and consists of the circular and linear contributions, which are dependent on and independent of the sign of the circular polarization, respectively. It was shown that the circular photocurrent is significantly higher than the linear photocurrent. It was established that, for both the circular and linear polarizations, the photocurrent is directly proportional to the power of the excitation radiation. For the linearly polarized laser radiation, the photocurrent depends on the polarization angle in accordance with the odd law. The regularities revealed are consistent with the mechanism of the generation of transverse photocurrent with the photon drag effect.

Polarization-sensitive photocurrent in the resistive Ag/Pd films

We report on the observation of helicity dependent photocurrent of the 20 μm thick silver-palladium (Ag/Pd) films manufactured by the thick-film technology. The transverse photocurrent is observed at oblique incidence of laser radiation with different wavelengths in the spectral range of 266 - 2100 nm. At the wavelength range of 532 - 2100 nm the polarity of the transverse photocurrent is positive (negative) for the left- (right-) circular polarized beam. We show that action of high temperature on the films in vacuum results in the decrease of longitudinal photocurrent due to the reduction of PdO content. The photon drag effect is suggested to be the origin of the polarization-sensitive photocurrent in the Ag/Pd films. The obtained results show that the Ag/Pd resistive films may be of interest for polarization- sensitive measurements.