Conduction mechanisms during the growth of Pd thin films: Experiment and model

Abstract

The conduction mechanisms in different growth stages of Pd thin films are investigated in detail. Special attention is paid to the transition regions between the different stages of film growth and the dominant conduction mechanisms. Mechanisms of thermally activated tunneling, percolation conduction, and continuous film conduction are considered and a consistent set of model parameters is deduced. This is done by also varying the substrates. Activation energies of tunneling on the order of 50 meV, percolation thresholds p(c)=0.70 +/- 0.01, and conduction exponents mu=2.43 +/- 0.12 were achieved. The physical meaning of the model parameters is discussed and connected mechanisms are proposed. The minimal film thicknesses of continuous RT-sputtered Pd films were found to be on the order of 1.5 nm.