PNNL

Abstract

Germanium is a small-gap semiconductor that efficiently absorbs visible light, resulting in photoexcited electrons predicted to be sufficiently energetic to reduce H2O and evolve H2 gas. In order to protect the surface from corrosion and prevent surface charge recombination in contact with aqueous pH 7 electrolyte, we grew epitaxial SrTiO3 layers of different thicknesses on p-Ge (001) surfaces. 4 nm SrTiO3 allows photogenerated electrons to reach the surface and evolve H2 gas, while 13 nm SrTiO3 blocks these electrons. Ambient pressure X-ray photoelectron spectroscopy indicates the surface readily dissociates H2O to form OH species, which may impact surface band bending.