Piezoelectric Pb(Zr-x,Ti1-x)O-3 thin film cantilever and bridge acoustic sensors for miniaturized photoacoustic gas detectors

Novel, highly sensitive piezoelectric acoustic sensors based on partially unclamped Pb(Zr-x, Ti1-x)O-3 (PZT) coated cantilever and bridge have been fabricated by silicon micromachining. High sensitivity at low frequencies (5-100 Hz) has been achieved by patterning very narrow slits (3 to 5 mum) around the structures. A typical response of 100 mV Pa-1 and a noise equivalent pressure of 1.6 mPa Hz(1/2) at 20 Hz have been measured using a 10 pF charge amplifier. Stress compensation, dry etching and integration of high performance piezoelectric thin films were the key issues. PZT/Pt/SiO2 stacks have been patterned by reactive ion etching and stress compensation has been achieved by compensating the PZT film's tensile stress by adjusting the thickness of a thermal SiO2 layer. The integration of sol-gel PZT films with a transverse piezoelectric coefficient e(31,f) of -12.8 C m(-2) has been realized without any degradation of the properties. The microphones were successfully integrated into a miniature photoacoustic detector and tested for CO2 detection. Concentrations down to 330 ppm could be measured with significant signals.

Published in:
Journal of Micromechanics and Microengineering, 14, 12, 1650-1658
Ledermann, N Ecole Polytech Fed Lausanne, Ceram Lab, Mat Inst, Fac Engn, CH-1015 Lausanne, Switzerland Ecole Polytech Fed Lausanne, Ceram Lab, Mat Inst, Fac Engn, CH-1015 Lausanne, Switzerland Hach Ultra Analyt, CH-1222 Vesenaz, Switzerland Siemens Bldg Div, CH-8505 Mannedorf, Switzerland
Times Cited:1
Cited References Count:25
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 Record created 2006-08-21, last modified 2018-03-17

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