Surface potential of ferroelectric thin films investigated by scanning probe microscopy

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Abstract
Scanning probe microscopy was used to form local polarized domains in ferroelectric thin films by applying a voltage between the gold-coated cantilever and the conductive substrate in contact mode. Two methods of visualizing the poled areas are described. The first is to detect the piezoelectric response of the films by applying a small oscillating voltage between the probe tip and the substrate. This measurement determines the local ferroelectric polarity and domain structure directly. The second method is to measure the surface potential of the poled films using scanning Maxwell stress microscopy. This does not directly address the ferroelectric behavior of the film, but rather the potential due to surface charge. We determined the surface potential dependence on pulse voltage and duration applied to the ferroelectric film. The results demonstrate that the charged area will increase rapidly, but the surface potential will saturate as the pulse voltage and duration are increased. The resultant stable localized surface charge features indicate that lead zirconate titanate thin films are promising candidates for high-density charge storage media.