Ion- irradiation is an established technology to change properties of diamonds in a controlled way  and has been studied as a function of ion species, energy and fluence for many years [2-4]. However, little is known regarding surface effects for irradiations with high energy ions which penetrate deep into the diamond. Irradiation experiments were carried out on various synthetic diamond samples using 14 MeV Au6+ ions and a maximal fluence of 2.4 ×1015 ions/cm2. The penetration depth of such ions in diamond is about 1.7 μm . The surface of the samples was characterized by atomic force microscopy (AFM), Raman spectroscopy and X-ray reflectometry (XRR).
Due to the irradiation, the formerly transparent samples darkened, which suggests partial amorphisation of the material. Raman spectroscopy revealed significant changes in the lattice dynamics and the formation of sp3 bonded amorphous carbon (Fig. 1). XRR experiments performed at beamline P08 @ PETRA III (Hamburg, Germany) revealed the formation of modified layers near the sample surface (Fig. 2). AFM provided information on changes of the surface topography including increased roughness and swelling. The surface roughness deduced from XRR data compared to AFM results will be discussed for the different diamond materials.
Fig. 1: Raman spectra of pristine (black lines) and irradiated (colored lines) diamonds for a single crystal diamond sample irradiated with 14 MeV Au-ions of different fluences.
Fig. 2: XRR curves for the experimental (black lines) and calculated (red lines) data of a single crystal diamond sample irradiated with 14 MeV Au-ions of fluence 2.4 × 1015 ions/cm2.
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