Chemical cleaning of iron and nickel single crystal surfaces and the removal of wall contaminants in ultrahigh vacuum systems by nitric oxide

Abstract

In this note we describe chemical cleaning procedures using exposures of NO, O2, and H2 on iron {112} and nickel {110} single crystal specimens which were subsequently used for ultrahigh vacuum (UHV) gas adsorption studies. The rationale for applying chemical cleaning rather than extensive ion etching cycles is to deplete the bulk of the materials of dissolved impurities more efficiently and to avoid or reduce ion induced damaging of the single crystal surfaces. We also describe our procedure to reduce wall contaminants in UHV systems by flowing nitric oxide through the system during bakeout, and the protection of single crystal specimens against bulk contamination by nitriding the samples with ammonia prior to exposure to air.