Comparison of Inorganic and Organic Acid Etching Processes on Germanium(100)

摘要

Ge(100) surfaces were cleaned in aqueous hydrochloric and citric acids. X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry were used to measure the surface composition and film thickness, respectively. Alkanethiolate self-assembled monolayers were formed after each acid treatment to assess oxide removal since sulfur only bonds with elemental Ge. XPS showed that sonication is required to remove citric acid species which remain on the surface after etching. The residual citric acid on the surface inhibits the liquid phase deposition of the alkanethiol layer likely by physically blocking surface sites. Aqueous hydrochloric acid etching removed more oxides from the surface, and the alkanethiol formed a dense monolayer.