Mechanical properties and structural integrity of devices based on sol–gel mesoporous oxides thin films.

One of the current issues in the development of devices based on porous thin films synthesized by sol gel is the eventual failure of the structural integrity of these systems due to chemical or mechanical stresses. In order to design and build robust systems, it is necessary to evaluate the role that each material forming the device has over its mechanical performance and chemical stability, considering their individual properties, their spatial arrangement, and the interfaces between them. In this work, the structural and mechanical evaluation of multilayers based on silica and titania mesoporous films is presented, and the variables that affect the structural integrity of these multilayered devices are evaluated. In addition, the chemical and mechanical stability of these optical devices against flow stress is assessed, simulating operating conditions of the sensors in a liquid environment. Single layer, bilayers, and multilayered devices were synthesized using the sol–gel method in combination with surfactant self-assembly, and their mechanical and structural properties were evaluated with electron and optical microscopy, X-ray reflectometry, and instrumented indentation. After these studies, improvements to the materials forming the device are proposed to maximize the structural integrity of the system. Highlights: Silica mesoporous films present a ductile behavior while titania mesoporous films are more brittle. The spatial disposition of SiO₂ and TiO₂ layers in bilayer structures modifies the failure mode. The mesoporous SiO₂–TiO₂ multilayer mechanical behavior is modulated by the SiO₂ layers. The optical and mechanical behavior of the photonic device changes after immersion in water at 40 °C. [ABSTRACT FROM AUTHOR]