Use of reactive ion sputtering to produce clean germanium surfaces in a carbon rich environment—an ion scattering study

We have used the ion spectroscopic techniques of direct recoil spectroscopy and mass spectroscopy of recoiled ions to demonstrate that low energy reactive ion sputtering of Ge is capable of removing surface impurities such as carbon. The experiments were performed in a vacuum chamber maintained at 3.5×10−7 Torr. At these pressures, physical sputtering using noble gas is not effective for cleaning Ge surfaces as carbon redeposits onto the surface. In this article, we demonstrate that reactive sputtering of Ge using 4.0 keV nitrogen at a Ge surface temperature of ∼740 K and above removes surface carbon and deposits nitrogen on the Ge surface. Heating the nitrogen exposed Ge surface to above ∼880 K results in the desorption of nitrogen and generates an atomically clean Ge surface, under poor vacuum conditions.