Mechanical investigations of free-standing SiN membranes patterned with one-dimensional photonic crystal structures

Abstract

A detailed investigation of the structural and vibrational properties of various prestressed silicon nitride membranes patterned with one-dimensional photonic crystal structures is presented. The tensile stress related deformation of the structure in the vicinity of the patterned area is determined by atomic force microscopy scans, while the resonance frequencies and quality factors of the out-of-plane membrane vibrations are measured using optical interferometry. We show that these noninvasive measurements, combined with the results of finite element simulations, provide accurate information on the tensile stress, the elasticity modulus, and the density of these nanostructured thin films. The obtained results are interesting in two ways: first, they show that such highly reflective thin membranes already exploited in various photonics applications possess high-mechanical quality, which also makes them attractive for optomechanics and sensing applications. Second, they represent a nondestructive method to determine key material parameters, which can be applicable to a broad range of fragile nanostructured thin films.