Hi,

  Piezoelectric thin film deposited on a micro cantilever
is used to activate the cantilever and simultaneously
sense the vibrating by derived piezoelectric charge.
  Because when the cantilever is bending, stress on
the top electrode should be different from the bottom
electrode. [Piezo film:1um thickness,cantilever:3 um]
  So, does piezoelectric charge density of top electrode
differ from that of bottom electrode?
  Have anybody measured different piezo charge density on the
top and bottom electrodes?  [Now I have some difficulty to
carry out such a experiment myself.]

Best wishes.