  We present a phenomenological model and Finite Element simulations to
describe the depth variation of mass density and strain of ion-implanted
single-crystal diamond. Several experiments are employed to validate the
approach: firstly, samples implanted with 180 keV B ions at relatively low
fluences are characterized using high-resolution X-ray diffraction (HR-XRD);
secondly, the mass density variation of a sample implanted with 500 keV He ions
well above its amorphization threshold is characterized with Electron Energy
Loss Spectroscopy (EELS). At high damage densities, the experimental depth
profiles of strain and density display a saturation effect with increasing
damage and a shift of the damage density peak towards greater depth values with
respect to those predicted by TRIM simulations, which are well accounted for in
the model presented here. The model is then further validated by comparing
TEM-measured and simulated thickness values of a buried amorphous carbon layer
formed at different depths by implantation of 500 keV He ions through a
variable-thickness mask to simulate the simultaneous implantation of ions at
different energies.
