Wavelength‐Dependent Photocurrent Generation Efficiency in the Carbon Nanowall Films

Abstract

Herein, the efficiency of generation of unipolar photocurrent pulses under action of obliquely incident nanosecond laser pulses is studied in carbon nanowall (CNW) films on silicon substrate depending on the direction of the wave vector and polarization of the laser radiation. The films consist of flake‐like graphite crystallites of nanometer thickness. Each of the crystallites comprises stacked graphene atomic sheets oriented mostly perpendicular to the substrate surface with random orientation in other directions. The angular and polarization dependencies of the longitudinal and transverse photocurrents at wavelengths of 266, 354.7, 532, and 1064 nm are measured. The longitudinal and transverse photocurrents are odd functions of the incidence angle, and, for a given angle of incidence, they are even and odd functions of the polarization azimuth, respectively. It is noteworthy that with the decrease in exciting radiation wavelength, the conversion coefficients of laser pulse power into longitudinal and transverse photocurrents increase and decrease, respectively. At wavelength of 266 nm, the transverse photocurrent changes its polarity, and the longitudinal photocurrent generated by s‐polarized radiation exceeds the p‐polarized radiation photocurrent. The obtained results are explained by morphology peculiarities of the CNW films and the surface photogalvanic effect photocurrent generation.