Ion-induced pattern formation on Co surfaces: An x-ray scattering and kinetic Monte Carlo study

Abstract

We report time-resolved grazing incidence small-angle x-ray scattering and atomic force microscope studies of the evolution of the surface morphology of the Co͑0001͒ surface during low-energy Ar ϩ ion sputtering. At temperatures greater than 573 K, the surface is smooth, erosion proceeding in either a layer-by-layer mode or a step retraction mode. In contrast, at temperatures below 573 K, the surface develops a correlated pattern of mounds and/or pits with a characteristic length scale,. At room temperature, the surface morphology is dominated by mounds, and coarsens as time progresses. The characteristic length scale obeys the apparent power law, ϭAϫt n with nϭ0.20Ϯ0.02. The rms roughness of the surface increases in time according to a similar power law with a slightly larger exponent ␤ϭ0.28Ϯ0.02. Kinetic Monte Carlo simulations of a simple model of Cu͑111͒ were also performed. These simulations suggest that mound formation and coarsening at low temperatures is due to the slow diffusion of sputter-created adatoms on step edges. The morphological transition from mounds to pits is associated with activation of kink diffusion. These simple simulations produce values for the scaling exponents that agree with the experimental measurements.

Ion-induced roughening and ripple formation on polycrystalline metallic films

“…Metallic surfaces can be further divided to polycrystalline (PC) and single-crystalline (SC) ones. Multiple studies on SC metals indicate that the role of the crystallinity in these systems is associated with the presence of the Ehrlich-Schwoebel (ES) barrier [3,[19][20][21][22][23][24].…”

Effect of Crystal Orientation on Self-Assembly Nanocones Formed on Tungsten Surface Induced by Helium Ion Irradiation and Annealing

“…In fact, when an ion beam is used to irradiate materials, the surface roughness is usually measured as a function of time and other system parameters. In addition, the results are used to obtain the exponents of the power-law function that are dependent on these experimental parameters [31,32]. …”

Mechanisms of pattern formation in grazing-incidence ion bombardment of Pt(111)

“…This change in the character of the ripple pattern with temperature is similar to the observed change from dot to pit patterns at normal incidence ion bombardment. 10,12,20 ͑vi͒ Finally, the ripple wavelength apparently stays roughly constant up to 450 K and then rapidly increases with temperature. This finding is corroborated by the quantitative analysis of Fig.…”

“…[9][10][11][12][13][14][15][16][17][18][19] At sufficiently high temperatures, the formation of pit patterns can be attributed to the creation of mobile surface vacancies and vacancy clusters, their aggregation to islands, and the action of a step edge barrier for surface vacancies. 10,[12][13][14][15][16][17][18][19][20] Coarsening behavior could be linked to material transport along step edges and the high temperature breakdown of pattern formation to the onset of step atom detachment. 13 Toward lower temperatures, a transition from pit to dot patterns is observed, which is linked to the mobility of adatoms and adatom clusters generated during bombardment, whereas surface and subsurface vacancy and vacancy cluster mobility ceases.…”

“…13 Toward lower temperatures, a transition from pit to dot patterns is observed, which is linked to the mobility of adatoms and adatom clusters generated during bombardment, whereas surface and subsurface vacancy and vacancy cluster mobility ceases. 10,12,20 Dot patterns on amorphous or ion beam amorphized surfaces ͑e.g., semiconductor surfaces͒ are usually described in terms of continuum theory. 5,21 This holds as well for the dot pattern created at off-normal incidence, but with sample rotation.…”