Datafiles for sputtering yields of impurity atoms implanted
into bulk materials as a function of impact energy, angle
and concentration of impurity atoms into the surface material.
Please note that these data are pure result of Monte Carlo
calculation, and they have not been benchmarked yet against
experimental sputtering yields of impurities implanted in
different bulk materials by different projectiles.    

Available projectiles:
D, He, B, N

Available implanted impurities:
He

Available targets:
W

The tables are calculated with the Monte Carlo program
trim.sp. The program assumes a nearly flat surface, a
statistically roughness in the order of a monolayer is
taken into account. The program assumes the impurity atoms
being uniformly implanted into a layer of surface material
until a given depth, which is reported in the tables.
Additionally the impurity atoms are assumed to have no
surface binding energy to the bulk material, meaning that
they are released as thermal particles.

The files named [projectile]_[impurity]_[target].y contain
the calculated sputtering yield, defined as the mean
number of sputtered impurity atoms per unity of incident
projectile ions.
The tables are arranged in rows providing the sputtering
yield of the implanted impurity (Y_imp) in function of
angle of incidence of the projectile, energy of the
projectile and impurity concentration into the surface
layer of material (C_imp, defined as N_imp/(N_bulk+N_imp)).
On top of the tables the values for the  atomic numbers
(Z) and the masses (m) of the projectile  (index 1) and
the impurity target atoms (index 2) are given, as well
as the depth of the assumed implantation profile.

The files named [projectile]_[impurity]_[target]_fit.y
contain the coefficients derived fitting the calculated
sputtering yield data with the Bohdansky formula
Y(E0)/C_imp = Q*Sn*(1-(Eth/E0)^(2/3))*(1-(Eth/E0))^2
where E0 is the projectile energy, and Q and Eth are
fitting parameters, contained in the tables for each
available value of the projectile incidence angle.
Sn is the nuclear stopping cross section, defined as
Sn = (0.5*log(1+1.2288*epsilon))/
     (epsilon+0.1728*sqrt(epsilon)+0.008*epsilon^0.1504)
epsilon is the reduced energy, defined as epsilon = E0/ETF,
where ETF = ((Z1*Z2*e^2)/(alpha_L))*((m1+m2)/(m2)) is the
Thomas-Fermi energy, in which Z1, Z2 are the nuclear charges,
and m1, m2 are the masses of the projectile and target atoms
respectively, and e is the electron charge. Finally, alpha_L,
defined as alpha_L = 0.4685*(Z1^(2/3)+Z2^(2/3))^(-1/2), in
angstrom, is the Lindhard screening length.
The increase of the calculated sputtering yield with the
impurity concentration in the material is roughly linear,
meaning that one single fit, giving Y(E0)/C_imp, can be
indeed used.

The original data and the fits are produced by K. Schmid,
Garching, September 2022.