The scanning microscope for semiconductor characterization (SMSC) : study of the influence of surface morphology on the photoelectrochemical behavior of an n-MoSe 2 single crystal electrode by photocurrent and electrolyte electroreflectance imaging

Abstract

Photocurrent and electrolyte electroreflectance (EER) measurements have been carried out, on a microscopic scale, in order to characterize the photoelectrochemical behavior of an n-MoSe 2 single crystal as a function of its surface morphology. Digital images of the surface distribution of these photoeffects have been obtained with the help of the scanning microscope for semiconductor characterization (SMSC). From the mathematical expressions describing both photoeffects, it is shown that the corresponding images yield complementary information about the semiconductor (sc)electrolyte interface, which can be related to the semiconductor topology. A comparative study is made on three different types of surface: (1) “as grown”, produced just after growing the single crystal; (2) “aged”, which results from the as-grown surface after working the electrode in the photoelectrochemical cell for some time; and (3) “freshly-peeled”, which is obtained by peeling off the upper sandwich layers of the aged sample. In the case of the aged surface, it is observed that electrochemical corrosion is detrimental for the photoelectrochemical behavior of the semiconductor, except on the sharp defects of its van der Waals surface. An explanation of this aging effect is proposed on the basis of the high anisotropy and structural parameters of this material.From EER images of the sc ¦electrolyte interface, the spatial distribution of the drop of the applied voltage at the Helmholtz layer is shown for the first time.