Surface potential of ferroelectric thin films investigated by scanning probe microscopy

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.

Imaging mechanism of piezoresponse force microscopy of ferroelectric surfaces

“…[73][74][75][76][77] Clearly, elucidating the charge effects in the PFM requires a reliable way to probe the local piezoresponse and long-range electrostatic forces simultaneously. This is especially important for investigations of dynamic phenomena in which large time intervals between sequential PFM-SSPM images are unacceptable.…”

Potential and Impedance Imaging of Polycrystalline BiFeO3 Ceramics

“…SPM has been successfully applied to semiconductor, 19 organic, 20 and ferroelectric 21,22 surfaces, as well as to defects, 23,24 and photoinduced 25,26 and thermal phenomena 27,28 in these materials. A number of SPM studies on grain boundary related phenomena have also been reported.…”

Dynamics of surface screening charges on domains of BiFeO3 films

“…It is widely believed that an overscreened surface occurs during bias-induced domain switching. 2,3,10 When a positive bias is applied on the ferroelectric films by a SPM tip, the ferroelectric polarization will points to the bottom electrode (downward-polarized). Electrons will be pulled away from the surface, and holes will accumulate and be trapped on the surface.…”

“…So far, adsorption and desorption of the surface screening charges 9 were seemed as a mechanism of SP decay process. Besides, sideways diffusion of screening charges and recombination with the opposite charges on adjacent domains 8,10 has also been proposed to play important roles in the SP decay process. Moreover, charge diffusion along the out-of-plane direction followed by the injection into the bottom electrode, as a possible mechanism, has not been ruled out yet.…”