Open Access Nano Express

Optimum deposition conditions of ultrasmooth silver nanolayers

Tomasz Stefaniuk1*, Piotr Wróbel1, Ewa Górecka2 and Tomasz Szoplik1

Author Affiliations

1 Faculty of Physics, University of Warsaw, Pasteura 7, Warsaw 02-093, Poland

2 Department of Chemistry, University of Warsaw, Żwirki i Wigury 101, Warsaw 02-089, Poland

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Nanoscale Research Letters 2014, 9:153  doi:10.1186/1556-276X-9-153

Published: 31 March 2014

Abstract

Reduction of surface plasmon-polariton losses due to their scattering on metal surface roughness still remains a challenge in the fabrication of plasmonic devices for nanooptics. To achieve smooth silver films, we study the dependence of surface roughness on the evaporation temperature in a physical vapor deposition process. At the deposition temperature range 90 to 500 K, the mismatch of thermal expansion coefficients of Ag, Ge wetting layer, and sapphire substrate does not deteriorate the metal surface. To avoid ice crystal formation on substrates, the working temperature of the whole physical vapor deposition process should exceed that of the sublimation at the evaporation pressure range. At optimum room temperature, the root-mean-square (RMS) surface roughness was successfully reduced to 0.2 nm for a 10-nm Ag layer on sapphire substrate with a 1-nm germanium wetting interlayer. Silver layers of 10- and 30-nm thickness were examined using an atomic force microscope (AFM), X-ray reflectometry (XRR), and two-dimensional X-ray diffraction (XRD2).

PACS

63.22.Np Layered systems; 68. Surfaces and interfaces; thin films and nanosystems (structure and nonelectronic properties); 81.07.-b Nanoscale materials and structures: fabrication and characterization

Keywords:
Thin films; Plasmonics; Roughness; Physical vapor deposition; Nanooptics