Local surface potential distribution in oriented ferroelectric thin films

Abstract

Using Kelvin force microscopy, the authors have investigated the potential distribution on ferroelectric films. The local distribution of potential was observed on downward, prepoled areas. The polarity of the potential corresponds to the screen charge. It was found that the electrical properties of the grain boundary affect the potential distribution. Most of the grain boundaries show a lower potential than the area inside the grain. The authors identified certain regions at the grain boundary with a very low potential. Such potential pits may act as efficient screen charge draining paths and may lead to important perturbations on the device level.

Origin of surface potential change during ferroelectric switching in epitaxial PbTiO3 thin films studied by scanning force microscopy

“…2,3,9 It is noted that the surfaces of the as-deposited films with the upward polarization as in the monodomain are screened by the negative screen charges being revealed as surface potential of 100-150 mV. As the positive voltage bias increases, the more negative charges, i.e., electrons, are injected and further accumulated as the extra screening charges.…”

“…1 There have been few attempts to observe nanoscale screen charge behaviors on the ferroelectric surfaces. [2][3][4][5] Kalinin and Bonnell 5 discussed the relationship between surface potential polarity and polarization orientation in as-deposited ferroelectric surfaces. Chen et al 2 reported the surface potential dependence on the pulse voltages, duration, and overscreened state of the poled regions in the written ferroelectric domains of Pb͑Zr, Ti͒O 3 thin films.…”

“…Origin of surface potential change during ferroelectric switching in epitaxial PbTiO 3 thin films studied by scanning force microscopy Yunseok Kim,1,2 Changdeuck Bae, 1 Kyunghee Ryu, 1 Hyoungsoo Ko, 3 Yong Kwan Kim, 3 Seungbum Hong, 4 and Hyunjung Shin 1 We investigated the surface potential of the ferroelectric domains of the epitaxial PbTiO 3 ͑PTO͒ films using both Kelvin probe and piezoresponse force microscopy. The surface potential changes as a function of applied biases suggested that the amount and sign of surface potentials depend on the correlation between polarization and screen charges.…”

A new non-destructive readout by using photo-recovered surface potential contrast

“…KPFM was used to study the surface charges dynamics process by imaging surface screening charge distribution 10,11 . Figure 1e displays the KPFM image for the patterned area shown in Fig.…”

“…A clear understanding of the behavior of surface charges after poling is crucial to utilizing ferroelectricity at the nanometer scale. Despite much of the work on the study of the SP of the ferroelectric materials [8][9][10][11][12] , relatively little emphasis has been placed on the readout method by measuring the non-contact SP in a ferroelectric memory, simply because the SP contrast (DSP) between oppositely polarized domains decays and fails to be kept as a memory, which is mainly due to the evolution and recombination of the movable surface charges 7,8,11,13 around the domain walls. So far, the room-temperature stability of DSP has not been succeeded, so the high density memory based on this concept faces critical challenge.…”