Nitrogen plasma cleaning of Ge(1 0 0) surfaces

We propose a dry method of cleaning Ge(1 0 0) surfaces based on nitrogen plasma treatment. Our in situ Auger electron spectroscopy (AES) and low-energy electron diffraction (LEED) analyses demonstrate that surface contamination remaining after wet treatment was effectively removed by nitrogen radical irradiation at low substrate temperatures. The nitrogen plasma cleaned Ge(1 0 0) surface shows a well-ordered 2 × 1 reconstruction, which indicates the formation of a contamination-free Ge(1 0 0) surface with good crystallinity. We discuss the possible reaction mechanism considering how chemisorbed carbon impurities are removed by selective C–N bond formation and subsequent thermal desorption. These findings imply the advantage of plasma nitridation of Ge surfaces for fabricating nitride gate dielectrics, in which we can expect surface pre-cleaning at the initial stage of the plasma treatment.