Q4. We have used a piezoelectric material sandwiched between two metal electrodes to detect the displacements of a silicon cantilever tip. The cantilever is
250\mu mlong,
20\mu mwide, and
2\mu mthick. The piezoelectric layer is
1\mu mthick and as wide as the cantilever and is extended over the first
10\mu mof the cantilever. For the piezoelectric material:
\epsi _(r)=1500,d_(31)=-44.2\times 10^(-12)(C)/(N)and
d_(33)=117\times 10^(-12)(C)/(N). For silicon,
E=170GPa. Ignore the effects of the metal electrodes and the piezoelectric layer in your mechanical calculations. a) Ignoring charge leakage, what is the produced charge on the top electrode if
\Delta y=1\mu m? b) What is the corresponding voltage difference across the electrodes if
\Delta y=1\mu m? Reminder: The produced voltage when a piezoelectric material is under stress
\sigma _(k)is found from:
V=(d_(3k)\sigma _(k))/(\epsi _(r)\epsi _(0))h_(piezo ), where
k=1or 3 and
h_(piezo )is the thickness of the piezoelectric layer.
