Ripple structures developed on graphite layers during ion‐sputtering

Abstract

AbstractSurface roughness caused by ion bombardment can influence the sputtering yield and deteriorate the depth resolution during depth profiling. In this work, the roughening of an amorphous graphite layer 60 nm thick on a Ta layer 50 nm thick deposited on a smooth silicon substrate was studied by atomic force microscopy (AFM). The AFM measurements were carried out on the surface of the as‐deposited sample, and after ion‐sputtering with a 1 keV ion beam at ion incidence angles of 22°, 49° and 71° in the middle of the carbon layers and at the C/Ta interfaces. Ion bombardment was performed with one and two ion beams on stationary and rotating samples with an initial surface roughness amplitude Ra of 0.13 ± 0.05 nm. On stationary samples, in the graphite layer as well as at the C/Ta interface, ripple formation on the nanometre scale was found at ion incidence angles of 49° and 71°. Depending on the sputtering parameters, the wavelengths of the ripples were found to be between 18.0 ± 4.0 and 31.4 ± 4.0 nm and the amplitude between 1.0 ± 0.2 and 4.9 ± 0.2 nm, yielding a roughness parameter Ra of between 0.4 ± 0.1 and 1.6 ± 0.1 nm measured over a 1 × 1 µm area. Unexpectedly, a stronger ripple formation in the graphite layer was found at a grazing ion incidence angle of 71°. The ripple formation is suppressed by sample rotation. Copyright © 2006 John Wiley & Sons, Ltd.