The role of electrochemical phenomena in scanning probe microscopy of ferroelectric thin films.

Applications of piezoresponse force microscopy and conductive atomic force microscopy to ferroelectric thin films necessitate understanding of the possible bias-induced electrochemical reactivity of oxide surfaces. These range from reversible ionic surface charging (possibly coupled to polarization) and vacancy and proton injection to partially reversible vacancy ordering, to irreversible electrochemical degradation of the film and bottom electrode. Here, the electrochemical phenomena induced by a biased tip are analyzed and both theoretical and experimental criteria for their identification are summarized.