Abstract
The cathodic decomposition of 
is studied by cyclic voltammetry and in situ ellipsometry. During the hydrogen evolution, an indium‐rich film grows on the surface of the semiconductor. Afterward, this film undergoes transformations between oxidized and reduced forms following the electrode polarization. A theoretical model based upon a three: "
or indium/electrolyte" or a four:
medium enables one to correctly interpret the ellipsometric data.