![]() In recent works, we have shown that in the Ag/Pd nanocomposite, one can observe both longitudinal and transverse polarization-sensitive photocurrent in a wide spectral range. Conductivity, size, and thickness of the Ag/Pd nanocomposite films may vary in a wide range, while their electronic properties can be controlled in the process the fabrication making these films very suitable for observation of the polarization-sensitive photocurrents. Being a metal-semiconductor nanocomposite, the Ag/Pd films consist of nanocrystallites of Ag-Pd solid solution, palladium oxide, and amorphous phase, including various oxides. The silver-palladium (Ag/Pd) nanocomposite films, which are widely used in electronics, are one of the materials where both SPGE and PDE can be observed. Usually, SPGE is accompanied by the PDE and bulk photogalvanic effect (for example, see references ). Experimentally SPGE has been demonstrated in gallium arsenide, copper crystal, and CuSe films. The theory of the SPGE has been developed in references. ![]() It is worth noting that this photocurrent vanishes if the excitation beam is s-polarized and/or if the reflection of electrons from the surface is specular, i.e., the x-component of the electron velocity does not change. Such an imbalance will result in a directed flow of electrons along the x-axis, i.e., the photocurrent will appear. Although, for the p-polarized beam, the probability of the photoexcitation will be the same for electrons moving toward and outwards the surface, the former will lose their momentum faster because of diffuse scattering on the surface. If the semiconductor bandgap is less than the photon energy, the probability of interband transitions will be proportional to ( E⋅ p) 2∝cos 2 ψ, where E is the electric field strength, p the electron quasimomentum, ψ is the angle between E and p. The microscopic mechanism of the SPGE can be explained by considering photoexcitation of the semiconductor with a p-polarized laser beam at oblique incidence ( Figure 1). The pronounced dependence of the photocurrent on the angle of incidence and polarization of the excitation beam opens avenues toward the development of polarization- and position-sensitive detectors for industrial and space applications. Obtained experimental results are in agreement with the developed phenomenological theory, which describes transverse and longitudinal photocurrents due to SPGE and PDE in terms of relevant second-order nonlinear susceptibilities and allows us to obtain their dependences on the angle of incidence and polarization of the excitation laser beam. Specifically, the irradiation of the film with the s-polarized excitation beam produces a monopolar photoresponse, while at p-polarized excitation, the photoresponse is bipolar, having a short front and long tail. However, the temporal profile of the transverse photocurrent pulse is monopolar at any polarization and angle of incidence, while the temporal profile of the longitudinal photocurrent pulse depends on the polarization of the excitation beam. It is shown that in both the transverse and the longitudinal configuration, the surface photogalvanic (SPGE) and photon drag effects (PDE) contribute to the observed photocurrent. We performed the investigation of the polarization-sensitive photocurrent generated in silver-palladium metal-semiconductor nanocomposite films under irradiation with nanosecond laser pulses at the wavelength of 2600 nm.
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