Temperature dependence in sputtering

A result has been obtained on the temperature dependence in sputtering of silver which is contrary to current views by taking steps to eliminate spurious effects due to changes of residual gas pressure and target temperature, and by determining the relevant energy range for thermal sputtering. The result is thought to be due basically to the thermal spike effect, and agreement is shown with a postulated thermal spike model, in which the instantaneous variation of spike temperature against thermal diffusivity is treated on the basis of Carslaw's solution of the normal heat conduction equation. The thermal diffusivity is shown to be proportional to the thermal conductivity subject to a constant metal density in the temperature range 300 to 500K and a heat capacity that obeys the Dulong-Petit law which holds good for most metals at high temperatures. The thermal conductivity versus preheat target temperature curve matches the Makinson electronic thermal conductivity curve for metals. (author)