Smooth Ag film deposited using e-beam evaporated Ge as an intermediate layer for applications in nanoscale devices and optical superlens

Abstract

In this paper, we highlight a new method to obtain smoother silver (Ag) film characterized by much smaller average RMS surface roughness of ∼0.7nm, peak-to-valley separation of ∼4nm and grain-size distribution ∼15nm as compared to conventionally obtainable Ag film characterized by RMS surface roughness of ∼10nm, peak-to-valley separation of ∼20nm and grain-size distribution of ∼100nm. Thin Ag films of ∼15nm (optically thin) were deposited on double-polished borosilicate glass and silicon (100) substrates with 2nm Germanium (Ge) intermediate layers. An optically thick Ag film of 60nm was also prepared with 2nm Ge. The Germanium thicknesses were also varied and similar surface morphology improvements are observable on all the samples. The AFM image analysis shows that having the evaporated Ge intermediate layer drastically changes the Ag surface morphology, namely, the surface roughness, peak-to-valley and grain size distribution. Our smooth Ag results are very promising for applications in molecular electronics interconnect, optical metamaterials, plasmonic superlens and nanophotonics. © 2007 Materials Research Society.