Surface potential of ferroelectric thin films investigated by scanning probe microscopy

Scanning probe microscopy was used to form local polarized domains in ferro electric thin films by applying a voltage between the gold-coated cantileve r and the conductive substrate in contact mode. Two methods of visualizing the poled areas are described. The first is to detect the piezoelectric res ponse of the films by applying a small oscillating voltage between the prob e tip and the substrate. This measurement determines the local ferroelectri c polarity and domain structure directly. The second method is to measure t he surface potential of the poled films using scanning Maxwell stress micro scopy. This does not directly address the ferroelectric behavior of the fil m, but rather the potential due to surface charge. We determined the surfac e potential dependence on pulse voltage and duration applied to the ferroel ectric him. The results demonstrate that the changed area will increase rap idly, but the surface potential will saturate as the pulse voltage and dura tion an increased. The resultant stable localized surface charge features i ndicate that lead zirconate titanate thin films are promising candidates fo r high-density charge storage media. (C) 1999 American Vacuum Society. [S07 34-211X(99)02405-1].