Theory of improved resolution in depth profiling with sample rotation

Abstract

We advance a theory that explains why sample rotation during depth profiling leads to a dramatic improvement in depth resolution. When the sample is rotated, the smoothing effects of viscous flow and surface self-diffusion can prevail over the roughening effect of the curvature-dependent sputter yield and generate a smooth surface. If the sample is not rotated initially and the depth resolution declines, we predict that subsequent rotation leads to improved resolution. This phenomenon has already been observed experimentally.

Numerical analysis of quantum dots on off-normal incidence ion sputtered surfaces

“…For substrate rotation at constant angular velocity ӷ 2 / D ͑D / 2 being the time it takes the ripple amplitude to grow significantly 18 ͒, the surface will be bombarded from all azimuthal directions before a ripple amplitude can become appreciable. 12 This is implemented by irradiating a static substrate 11 and choosing randomly from the interval 0 ഛ Ͻ 2.…”

Theory of ripple topography inhibition in depth profiling with sample rocking

“…16,17 It has been known for many years that sample rocking about a line in the surface orthogonal to the ion flux direction or sample rotation about the surface normal can reduce surface roughening in sample thinning for transmission electron microscopy investigation 18 and both these modes have been modelled analytically 18,19 for large amplitude roughness situations. More recently sample rotation has been successfully employed to inhibit ripple formation 20,21 on sputtering eroded materials and this process has been modeled by Bradley & Cirlin 22 and Bradley. 23 It is the purpose of the present study to develop a similar analysis for the sample rocking mode and, in particular, to consider the role of ballistically motivated surface atomic diffusion.…”

Effect of surface-height derivative processes on ion-bombardment-induced ripple formation

“…Bradley and Cirlin 17 have given a partial assessment of the competition of the terms including the first in Eq. ͑1͒ and with mϭ0 and nϭ1 and 2; their approach is extended here.…”