title: Imaging Ferroelectric Domains and Domain Walls Using Charge Gradient Microscopy: Role of Screening Charges.
abstract: Advanced scanning probe microscopies (SPMs) open up the possibilities of the next-generation ferroic devices that utilize both domains and domain walls as active elements. However, current SPMs lack the capability of dynamically monitoring the motion of domains and domain walls in conjunction with the transport of the screening charges that lower the total electrostatic energy of both domains and domain walls. Charge gradient microscopy (CGM) is a strong candidate to overcome these shortcomings because it can map domains and domain walls at high speed and mechanically remove the screening charges. Yet the underlying mechanism of the CGM signals is not fully understood due to the complexity of the electrostatic interactions. Here, we designed a semiconductor-metal CGM tip, which can separate and quantify the ferroelectric domain and domain wall signals by simply changing its scanning direction. Our investigation reveals that the domain wall signals are due to the spatial change of polarization charges, while the domain signals are due to continuous removal and supply of screening charges at the CGM tip. In addition, we observed asymmetric CGM domain currents from the up and down domains, which are originated from the different debonding energies and the amount of the screening charges on positive and negative bound charges. We believe that our findings can help design CGM with high spatial resolution and lead to breakthroughs in information storage and energy-harvesting devices.
authors.affiliation: Center for Nanoscale Materials and ‡Materials Science Division, Argonne National Laboratory, Argonne National Laboratory , Lemont, Illinois 60439, United States.
authors.forename: Sheng
authors.initials: S
authors.lastname: Tong
authors.affiliation: Center for Nanoscale Materials and ‡Materials Science Division, Argonne National Laboratory, Argonne National Laboratory , Lemont, Illinois 60439, United States.
authors.forename: Il Woong
authors.initials: IW
authors.lastname: Jung
authors.affiliation: Center for Nanoscale Materials and ‡Materials Science Division, Argonne National Laboratory, Argonne National Laboratory , Lemont, Illinois 60439, United States.
authors.forename: Yoon-Young
authors.initials: YY
authors.lastname: Choi
authors.affiliation: Center for Nanoscale Materials and ‡Materials Science Division, Argonne National Laboratory, Argonne National Laboratory , Lemont, Illinois 60439, United States.
authors.forename: Seungbum
authors.initials: S
authors.lastname: Hong
authors.affiliation: Center for Nanoscale Materials and ‡Materials Science Division, Argonne National Laboratory, Argonne National Laboratory , Lemont, Illinois 60439, United States.
authors.forename: Andreas
authors.initials: A
authors.lastname: Roelofs
keywords: atomic force microscopy; electrostatic force; focused ion beam; periodically poled lithium niobate