Ferroelectric Thin Film Capacitors, The Distribution Of Scanning Probe Microscopy Study

Recent progresses in ferroelectric devices necessitate an understanding of local ferroelectric properties on the nanometer level. This has motivated a number of studies of ferroelectric materials with various scanning probe microscopies (SPM). The natures of the probe and formation mechanisms in these techniques are different; therefore, the images of SPM can reflect different properties of sample surface. In this work, related properties of ferroelectric thin film were investigated as followed:The main factors determining the image formation of piezoresponse force microscopy (PFM) and scanning nonlinear dielectric microscopy (SNDM) were studied. To avoid the misreading of the same conductive tip with different state, a new method of polarization distribution mapping with nonconductive tip was proposed, and the result of experiment demonstrated that the polarization distribution of ferroelectric thin films could be characterized well by the new approach.At present, local morphology was used to discriminate ferroelectric phase area and non-ferroelectric phase area, but once morphology variation of phase transformation was tiny, the ferroelectric phase area and non-ferroelectric phase area was hard to discriminate only from morphology view. However, the introduction of SNDM can overcome this limitation, and visualize the investigation of annealing process. Combining X-ray diffraction, atomic force microscopy (AFM) with SNDM, the phase transformation process of PZT thin films with different annealing time and of PLT films with different annealing temperature were studied, respectively.Based on SNDM technique, a method of local capacitance-voltage characteristic characterization of ferroelectric thin films was proposed. The effect of traps at oxide-semiconductor interface on metal-oxide-semiconductor structure capacitance-voltage curve was discussed, and the influence of coercive field to the capacitance-voltage characteristics of ferroelectric thin films was also discussed. The dynamic switching of ferroelectric domain in Ca doping (Pb,La)TiO3 thin film was studied by SNDM from the view of electricity. It is found that the movement...