Optical Readout of Silica Mesoporous Thin Films Mechanical Properties Using Plasmonic Nanoantennas

HILARIO D. BOGGIANO; JUAN IGNACIO RAMALLO; LIN NAN; ANDRÉS LITWILLER; EMILIANO CORTÉS; STEFAN A. MAIER; GUSTAVO GRINBLAT ; MARÍA CECILIA FUERTES ; PAULA C. ANGELOMÉ; ANDREA V. BRAGAS

ACS Photonics

American Chemical Society

Año: 2023 vol. 10 p. 3998 - 4005

2330-4022

In this work, we apply the recently developed FREquency Shift of nanoAntennas (FRESA) technique to measure the Young’s modulus of ultrathin mesoporous films at GHz frequencies as a function of porosity with local precision. The method measures changes in the mechanical oscillation frequency of optically excited plasmonic nanoantennas when modifying their surrounding medium. The values obtained range from 4 to 10 GPa for porosities extending from 4% to 35%, compatible with reports on films grown in similar conditions. We further find comparable results when using the well-established nanoindentation (NI) technique, validating the new method. By analyzing the nanoresonator´s quality factor, the measurement reveals an excellent interfacial adhesion of the films to the nanoantennas. Different to most other characterization techniques, FRESA provides elastic modulus determination at GHz frequencies, relevant for the operation of current devices. Furthermore, FRESA exhibits, in principle, no limitations in terms of film thickness, in contrast to NI, which is strongly affected by the stiffness of the substrate for ultrathin films.