Diffusion of silver in 6H–SiC and polycrystalline CVD-SiC was investigated using

α-particle channelling spectroscopy and electron microscopy. Fluences of 2 x

1016cm−2 of 109Ag+ were implanted with an energy of 360keV at room temperature,

at 350C and 600C, producing an atomic density of approximately 2% at the

projected range of about 110nm. The broadening of the implantation profile and

the loss of silver through the front surface during vacuum annealing at up to 1600C

was determined. Fairly strong silver diffusion was observed after an initial 10h

annealing period at 1300C in both polycrystalline and single crystalline SiC, which

was mainly due to implant induced radiation damage. After further annealing at

this temperature no additional diffusion took place in the 6H–SiC samples, while it

was considerably reduced in the CVD-SiC. The latter was obviously due to grain

boundary diffusion and could be described by the Fick diffusion equation.

Isochronal annealing of CVD-SiC up to 1400C exhibited an Arrhenius type

temperature dependence, from which a frequency factor of about 4 x 10−12m2/s and

an activation energy of about 4 x 10−19J could be extracted. Annealing of 6H–SiC

above 1400C shifted the silver profile without any broadening towards the surface,

where most of the silver was released at 1600C. Electron microscopy revealed that

this process was accompanied by significant re-structuring of the surface region.

An upper limit of D<10−21m2/s was estimated for 6H–SiC at 1300C.

Study of Silver Diffusion in Silicon Carbide. E.Friedland, J.B.Malherbe, N.G.van

der Berg, T.Hlatshwayo, A.J.Botha, E.Wendler, W.Wesch: Journal of Nuclear

Materials, 2009, 389[2], 326-31