Angular Dependences of Silicon Sputtering by Gallium Focused Ion Beam

Angular dependences of the surface layer composition and the sputtering yield of silicon upon irradiation of the surface with a focused beam of gallium ions with an energy of 30 keV are obtained. The surface composition is analyzed by scanning Auger electron spectroscopy (SAES) and secondary ion mass spectrometry (SIMS). The sputtering yields are determined by measuring the volume of sputtering craters and irradiation doses. It is found that the content of gallium in the surface layer is about 30 at % with incidence angles close to the normal. With incidence angles greater than 30°, the concentration of gallium decreases quite sharply. The angular dependence of the sputtering yield of silicon does not correlate with the content of gallium in the surface layer and is rather well described by the cascade sputtering mechanism proposed by P. Sigmund.