The electrochemical etching of (110) n-Si surfaces in aqueous NH 4 F has been studied for the first time by in situ atomic resolution scanning tunneling microscopy. It was found that the degree of interfacial order was profoundly dependent upon applied potential. At potentials near or positive of the open-circuit potential, pit corrosion occurred that resulted in disordered surfaces. At potentials negative of the open-circuit potential, highly anisotropic layer-by-layer dissolution took place that rendered a rough surface atomically flat. The scanning tunneling microscopy images clearly showed an interfacial structure characterized by zigzag chains along the <110> direction. The distance between every other Si atom on the zigzag chain was measured to be 3.8 A, while the chain periodicity was determined to be 5.4 A. These values serve to establish that controlled negative-potential etching resulted in the formation of an ideal H-terminated (110) Si:H -(1 x 1) structure. Time-dependent scanning tunneling microscopy was employed to gain insight into the role of dihydride Si atoms in the anisotropic etching process. High-resolution images allowed the evaluation of absolute etching rates along the <110> direction through an exact numerical count of the Si atoms dissolved per unit time.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.