Ion bombardment of a sinusoidal wave geometry. Ion flux density, J, incident at an angle θ with respect to mean surface plane is shown. Local surface gradient, tan . Sinusoidal wave is described by h = h0 sin(2πx/λ), where λ is the wavelength of the ripples, and h0 is the amplitude.
Basu et al. Nanoscale Research Letters 2013 8:289 doi:10.1186/1556-276X-8-289