Fundamentals of Ion-Solid Interaction - SPIRIT

Collisional Damage – High Fluence
At increasing fluence, newly generated Frenkel pairs may
annihilate with previously generated ones (typical for metals)
c
(assuming that affected depth is ~2·R p)
In materials with covalent binding (e.g., semiconductors), lattice damage might increase
until amorphization. A simple formal estimate for the fluence required for amorphization is
obtained when each atom in the irradiated volume has been displaced once in average,
i.e. the FP concentration becomes equal to the atomic density of the irradiated material
dpa
dpa
eff
E0 , NF
E0
1 cF
a
d
2R
E
F V
am
2nR
N
cF
n
p
eff
F
E0
E
0
p
eff
NF
2nR
E0
E
p
0
n atomic density
0
ion fluence
V a annihilation volume (for metals,
typically 20…50 atomic volumes)
R p mean projected ion range
Correspondingly, in radiation damage studies the fluence is often given in units of
dpa = displacements per atom
Ion Fluence
Institute of Ion Beam Physics and Materials Research Prof. Wolfhard Möller
Frenkel Pair Concentration
V a -1
0