SEM analysis of ion implanted SiC
Malherbe, Johan B.; Van der Berg, Nic (Nicolaas George); Friedland, Erich Karl Helmuth; Hlatshwayo, Thulani Thokozani; Kuhudzai, Remeredzai Joseph; Wendler, E.; Wesch, W.; Chakraborty, P.; Botha, A.J.; Da Silveira, E.F.
SiC is a material used in two future energy production technologies, firstly as a photovoltaic layer to harness
the UV spectrum in high efficient power solar cells, and secondly as a diffusion barrier material for
radioactive fission products in the fuel elements of the next generation of nuclear power plants. For both
applications, there is an interest in the implantation of reactive and non-reactive ions into SiC and their
effects on the properties of the SiC. In this study 360 keV Ag+, I+ and Xe+ ions were separately implanted
into 6H–SiC and in polycrystalline SiC at various substrate temperatures. The implanted samples were
also annealed in vacuum at temperatures ranging from 900 C to 1600 C for various times. In recent
years, there had been significant advances in scanning electron microscopy (SEM) with the introduction
of an in-lens detector combined with field emission electron guns. This allows defects in solids, such as
radiation damage created by the implanted ions, to be detected with SEM. Cross-sectional SEM images of
6H–SiC wafers implanted with 360 keV Ag+ ions at room temperature and at 600 C and then vacuum
annealed at different temperatures revealed the implanted layers and their thicknesses. A similar result
is shown of 360 keV I+ ions implanted at 600 C into 6H–SiC and annealed at 1600 C. The 6H–SiC is not
amorphized but remained crystalline when implanting at 600 C. There are differences in the microstructure
of 6H–SiC implanted with silver at the two temperatures as well as with reactive iodine ions. Voids
(bubbles) are created in the implanted layers into which the precipitation of silver and iodine can occur
after annealing of the samples. The crystallinity of the substrate via implantation temperature caused differences
in the distribution and size of the voids. Implantation of xenon ions in polycrystalline SiC at
350 C does not amorphize the substrate as is the case with room temperature heavy ion bombardment.
Subsequent annealing of the implanted polycrystalline samples leads to increased thermal etching effects
such as grain boundary grooving. Damage due to channelling (or non-channelling) in the different crystallites
resulted also in differences in thermal etching in the crystallites.