Features of the Formation of Ripple Structures on the Surface of Silicon under Irradiation with a Focused Gallium Ion Beam

The processes of microrelief formation on the Si (100) surface under irradiation with a 30-keV Ga+-ion beam with doses of D = 6 x 10(16)-4 x 10(18) cm(-2) at incidence angles of 0 = 0 degrees-50 degrees are studied. It is established that a ripple structure is formed in an angular range of 0 = 25 degrees-35 degrees at D = 2 x 10(17)-2 x 10(18) cm(-2). However, a well reproducible ripple structure is observed at incidence angles of 0 = 30 degrees +/- 2 degrees starting from irradiation doses of 2 x 10(17) cm(-2). As D increases from 2 x 10(17) to 2 x 10(18) cm(-2), the wavelength and the amplitude increase from similar to 150 to similar to 400 nm and from similar to 30 to similar to 70 nm, respectively. At D > 2 x 10(18) cm(-2), the ripple structure is destroyed. The features of the formation of such a Si surface relief using a Ga+-ion beam are a rather narrow angular range in which the relief is formed and the value of the irradiation dose at which its nucleation begins. The reasons for these features can be precipitates of implanted Ga in the Si surface layer and the angular dependences of the sputtering yield and composition of the Si surface layer irradiated with a Ga+ ion beam.