THE TEMPERATURE-DEPENDENCE OF THE SPUTTERING YIELD OF NOBLE-METALS

Abstract

The temperature-dependent sputtering yield of noble metals has been measured by some investigators as a function of the target temperature, or oppositely as an inverse relationship. One of the present authors has shown theoretically, as well as experimentally, that this dependence on temperature for one of the noble metals, silver, is an inverse relationship. In proving this in our previous report, Carslaw's solution of the heat conduction equation was employed in the theoretical development of the thermal spike model, and an inverse relationship was shown to exist under the assumption that the 'exponential term in the solution is nearly unity'. We have subsequently reconfirmed by calculation that the exponential term is nearly unity. In the present paper, we have added the experimental results showing the tendency of temperature-dependent sputtering phenomenon. It is also confirmed that the surface layer of the silver target is purified during thermal sputtering. This purification increases the electronic thermal conductivity of the layer; hence this effect supports the establishment of the thermal spike model.