Synthesis and Spectroellipsometric Characterization of Y₂O₃-stabilized ZrO₂-Au Nanocomposite Films for Smart Sensor Applications

Abstract

Noble metal nanoparticles exhibit significant potential in all-optical, smart-sensing applications due to their unique optical properties. In particular, gold (Au) nanoparticles exhibit a strong surface plasmon resonance (SPR) band, the spectral position and shape of which depends on the size, shape, and density of the nanoparticles and the physical and chemical properties of surrounding environment. Embedding the nanoparticles in an yttria-stabilized zirconia (YSZ) matrix is believed to expand their range of operation to temperatures above 500 °C. YSZ is a material that has been proven suitable for optical applications due to its high refractive index, low absorption coefficient and high transparency in the visible and infrared regions. Thus, its use as a base platform for nanocomposite thin films is expected to provide significant benefits in the development of harsh environment multifunctional sensors.In this work YSZ-Au nanocomposite films were synthesized from a YSZ and a Au target by the radio frequency magnetron co-sputtering technique in combination with a post-deposition annealing treatment in an argon atmosphere, with the annealing temperature being varied from 500-1000 °C in steps of 100 °C. The microstructure and the optical properties of the resulting films were characterized by x-ray diffraction spectroscopy, scanning electron microscopy and spectroscopic ellipsometry. Results on the effect of the Au particle size on the real and the imaginary part of the refractive index of the nanostructured composites are presented. Future smart sensor systems utilizing these multifunctional material sets for harsh environment sensing applications will likewise be outlined.

Particle Size Sensitivity Dependence of Nanocomposites for Plasmonic-Based All-Optical Sensing Applications

“…γ is a value that simply needs to be set as a constant for the fitting procedure, though the magnitude will not affect the fit if the values are on the order of those expected for LSPR. ε m was set using values determined through spectroscopic ellipsometry measurements of YSZ and [V O •• ] 0 was determined using the Y 2 O 3 doping of the YSZ target used during PVD depositions, assuming that there will be one oxygen ion vacancy created for every two yttrium atoms. The parameters K Ads , K Inc , and [V O(s) × ] 0 were used as fitting constants and the resulting values are also listed in Table along with the χ 2 for each fit.…”