A study of the secondary-ion yield change on the GaAs surface caused by the O+2 ion-beam-induced rippling

Abstract

The oxygen ion-beam-induced ripples observed during depth profiling of the GaAs surface by secondary-ion mass spectrometry has been studied by scanning tunneling microscopy. Under the O+2 primary-ion bombardment with energy of 10.5 kV at an incident angle of 37°, ripples of wavelength of 230 nm with the ridge lines perpendicular to the beam direction are formed, and they are grown to ∼80 nm in amplitude on the sputtered surface. Secondary-ion intensity changes abruptly in accordance with the development of ripples when they reach an amplitude of 30–50 nm. The phenomenon occurs only when the primary beam direction is perpendicular to the ridge orientation. It suggests that the ion yield enhancement is effected by increase of local concentration of oxygen implanted onto the rippled surface. Dependence of the enhancement on sputtered elements also seems to agree with the proposed mechanism.

Morphology of ion-sputtered surfaces

“…These results were corroborated by Karen et al [8][9][10], who investigated ripple formation on GaAs surfaces under bombardment with 10.5 keV O + 2 ions. They found that ripple formation takes place for angles of incidence between 30…”

“…Furthermore, in Refs. [8][9][10] it was unambiguously shown that the process of ripple formation is not caused by defects or inherited irregularities on the surface, but is determined merely by the primary ion characteristics. These results indicate that ripple formation is independent of microscopic details and the surface chemistry.…”

“…[8][9][10]. The experiments indicate that the ripple wavelength is linear in the energy, following ℓ ∼ ǫ cos θ.…”

Nanostructures on surfaces by ion irradiation

“…These authors conclude from their results [60] that for a full description of the erosion process on single crystal metals it is necessary to introduce in the theoretical models a realistic diffusion term, taking into account the presence of a Schwoebel barrier as it is familiar in film growth. Very well ordered nanostructures have been observed on semiconductor surfaces and the evolution of these features and their dependence on various ion-beam parameters has been studied in considerable detail [69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85]. For a given material, the type of pattern that is created may depend pronouncedly on the ion's energy and incidence angle.…”

Topography effects and monatomic ion sputtering of undulating surfaces, particles and large nanoparticles: Sputtering yields, effective sputter rates and topography evolution

“…Scaling laws for these ripples are described, for example, by Rusponi et al [17] and by Mayer et al [18] Other structures appear as a result of decomposition of compounds. [19] Bradley and Harper's theory was extended by Makeev and co-workers [20,21] and provided an explanation of the ripples induced by O 2 + primary ions on Si surfaces seen, for example, by Wittmaack [22] and later workers [23,24] although, in that case, conversion of the surface layer to an oxide is important. Much of this is described in the clear and recent work of Pahlovy et al [25] In 1983, Yamamura and co-workers [26] analyzed most extant measurements for the angular dependence of the sputtering yield and developed a general model.…”