Target 2 current and deposition speed

The substrate was located over target 2 and the deposition rate R and the current of the primary ions, sputtering with controlled ion energy (Wion) had been measured. Copper targets had been sputtered by argon at 10-2 mbar at 80 W.

The currents show no change with acceleration of the primary ions (by U2) and stay constant at an ion energy range between 250 and 800 eV. That means, the number of primary ions is not changed with their energy.

But the deposition speed shows a significant increase with the primary ion energy.

Target currents in dependence from the primary ion energy

Deposition speed in dependence from the primary ion energy

Estimation of the behavior of the Sputter Yield at target 2:
The deposition rate R was measured there with a quartz monitor (--> deposited mass proportional to deposited atom number).
The current at target 2 (I2) is proportional to the number of sputtered ions.  Then the sputter yield is nearly proportional to:
              Yexp(Wion) ~ R/I2
The figure shows good agreement between theoretical [6] and experimental sputter yield for four target materials (ITO, copper, graphite, silicon).

References

[6] https://www2.iap.tuwien.ac.at/www/surface/sputteryield

Estimated sputter yield in dependence from the primary ion energy for several target materials in comparison to the theoretical yield [6]