Active surface geometrical control of noise in nanowire-SAW sensors

ZnO nanowires were grown on equal areas of the active surface of a surface acoustic wave (SAW) sensor, using a range of patterns: parallel lines, perpendicular lines, curved stripes and a fully covered square zone. The sensor's frequency shift proved to be a geometry-independent parameter while noise depended significantly on geometry. A 2.5-fold variation in noise was obtained between the best (parallel stripes) and worst (compact area) patterns. A film deposited over such structures led to a further increase in noise, up to a comparable and pattern-independent value. Correlating the frequency shift increase with the sensor's covered active area, our results suggest that patterns with a filling factor above 40% could enhance SAW sensor performance via efficient noise reduction. (C) 2016 Elsevier B.V. All rights reserved.