Love-Wave devices with continuous and discrete nanocrystalline diamond coating for biosensing applications

Abstract The integration of diamond layers brings biocompatibility and enhanced stability of biomolecules to Love wave devices for promising biosensor applications. Love-Wave Surface Acoustic Wave (LW-SAW) devices consisting of an ST-cut quartz substrate with a silicon oxide layer coated by a thin diamond layer have been fabricated. The effect of nucleation and growth of diamond on the properties of LW-SAW devices was studied. The Love-wave phase velocity was shown to be affected by the diamond coating and dependent on its thickness. Experimental results are in a good agreement with simulations carried out with COMSOL Multiphysics software. Deposition of isolated diamond grains results in a reduction in velocity in the Love waves, which is attributed to a mass loading effect. Conversely, coalesced diamond layers increase the stiffness of the surface, which results in faster propagation of the Love waves. Improved entrapment of the Love waves in the guiding layer was observed in the case of isolated diamond grains, which should ensure higher sensitivity for this type of coating. Diamond coated LW-SAW devices can be used for biosensing applications with appropriated functionalization of the diamond surface.