The effect of atmospheric oxide thermodesorption on negative-ion atomic and cluster sputtering of silicon single crystal by cesium ions
Аннотация
The temperature dependences of the sputtering of negative ions of silicon-oxygen clusters were studied for the first time by the method of ultrahigh-vacuum mass spectrometry of secondary ions. In the temperature range of 100–200°C, an increase is observed, then after a maximum at 200°C to 800°C, the yield of negative-ion clusters of suboxide and silicon dioxide decreases exponentially. In this case, the yield of silicon oxide clusters stops, while yields of suboxide are still observed. The yields of negative oxygen ions correlate with the temperature dependences of the yield of silicon–oxygen clusters and show the presence of oxygen adsorbed on the surface and dissolved in the bulk. In this work, for the first time, to assess the contribution of these processes, a signal from negatively charged silicon dimers, which are an adsorbed silicon atom on a silicon atom at a substrate lattice site, was used. We have discovered the temperature dependence of thermal desorption of negatively charged silicon trimers. In our opinion, this signal represents a decay negative cluster ion of a surface defect center, the so-called Pb-center, of an adsorbed silicon tetramer — three silicon atoms on surface, closed at the top by a silicon addition atom.