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Gravimetric sensors operating at 1.1 GHz based on inclined c-axis ZnO grown on textured Al electrodes

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Rughoobur, G 
DeMiguel-Ramos, M 
Escolano, J-M 
Iborra, E 
Flewitt, AJ 


Shear mode solidly mounted resonators (SMRs) are fabricated using an inclined c-axis ZnO grown on a rough Al electrode. The roughness of the Al surface is controlled by changing the substrate temperature during the deposition process to promote the growth of inclined ZnO microcrystals. The optimum substrate temperature to obtain homogeneously inclined c-axis grains in ZnO films is achieved by depositing Al at 100 °C with a surface roughness ~9.2 nm, which caused an inclination angle of ~25° of the ZnO c-axis with respect to the surface normal. Shear mode devices with quality-factors at resonance, Q r and effective electromechanical coupling factors, [Formula: see text], as high as 180 and 3.4% are respectively measured. Mass sensitivities, S m of (4.9 ± 0.1) kHz · cm(2)/ng and temperature coefficient of frequency (TCF) of ~-67 ppm/K are obtained using this shear mode. The performance of the devices as viscosity sensors and biosensors is demonstrated by determining the frequency shifts of water-ethanol mixtures and detection of Rabbit immunoglobin G (IgG) whole molecule (H&L) respectively.



0306 Physical Chemistry (incl. Structural)

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Scientific Reports

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Nature Publishing Group
The research leading to these results has received funding from the European Community’s Horizon 2020 Programme under Grant Agreement No. SPIRE-01-2014-636820, the IC1208 Cost action, and from the Ministerio de Economía y Competitividad del Gobierno de España through the project MAT2013-45957-R. Financial support from these institutions is therefore gratefully acknowledged. G.R. also wishes to acknowledge funding from the Cambridge Commonwealth, European and International Trust.