Phase compositions, optical and photovoltaic properties of nanocomposite films based on Se and Cu

Se-Cu nanocomposite films were synthesized on glass substrates in vacuum by sequential evaporation of Se and Cu granules. It is shown that depending on the mass of evaporated Cu and the subsequent thermal treatment of the synthesized films, it is possible to obtain textured film structures consisting of different phases of selenium and copper selenide, including CuSe2, CuSe, Cu3Se2, Cu2Se and also nanosized Cu particles. Spectra of the refractive index, extinction coefficient and absorption index as well as spectra of coefficients of real and imaginary parts of dielectric permittivities of the synthesized films in the wavelength range lambda = 240-2500 nm were determined by spectroscopic ellipsometry. The real dielectric permittivities of the films are negative at lambda > approximate to 1000 nm, which shows that the synthesized films belong to plasmonic materials. It was found that the irradiation of the synthesized films by nanosecond laser pulses in a wide wavelength range of 266-1064 nm leads to generation of the photovoltage pulses sensitive to the direction of the wave vector, polarization, and the sign of the circular polarization of the laser pumping with their amplitude significantly increasing after the thermal treatment of the films. The observed photovoltage pulses are explained by the surface photogalvanic effect and the photon drag effect.