Island-to-percolation transition during the room-temperature growth of sputtered nanoscale Pd films on hexagonal SiC

摘要

We have studied the growth of room-temperature sputtered Pd films on 6H-SiC by using the atomic force microscopy technique. In particular, we analyzed the Pd film surface morphology as a function of the film thickness from 3 to 72 nm observing that the Pd grows initially (thickness 2-12 nm) as three-dimensional (3D) islands. Then (thickness 12-36 nm) the Pd film morphology evolves from compact 3D islands to partially coalesced wormlike structures, followed (36-60 nm) by a percolation morphology and finally to a continuous and rough film (at 72 nm). The application of the interrupted coalescence model allowed us to evaluate the critical mean islands diameter R_c ≈ 6.6 nm for the partial coalescence process while the application of the kinetic freezing model allowed us to evaluate the room-temperature Pd surface diffusion coefficient D_s ≈ 1.4 × 10~(-17) m~2/s on 6H-SiC. Finally, the application of the Vincent's model allowed us to evaluate the critical Pd coverage P_c=68% for the percolation transition.