Structural Consequences of Ferroelectric Nanolithography

Abstract

Domains of remnant polarization can be written into ferroelectrics with nanoscale precision using scanning probe nanolithography techniques such as piezoresponse force microscopy (PFM). Understanding the structural effects accompanying this process has been challenging due to the lack of appropriate structural characterization tools. Synchrotron X-ray nanodiffraction provides images of the domain structure written by PFM into an epitaxial Pb(Zr,Ti)O(3) thin film and simultaneously reveals structural effects arising from the writing process. A coherent scattering simulation including the superposition of the beams simultaneously diffracted by multiple mosaic blocks provides an excellent fit to the observed diffraction patterns. Domains in which the polarization is reversed from the as-grown state have a strain of up to 0.1% representing the piezoelectric response to unscreened surface charges. An additional X-ray microdiffraction study of the photon-energy dependence of the difference in diffracted intensity between opposite polarization states shows that this contrast has a crystallographic origin. The sign and magnitude of the intensity contrast between domains of opposite polarization are consistent with the polarization expected from PFM images and with the writing of domains through the entire thickness of the ferroelectric layer. The strain induced by writing provides a significant additional contribution to the increased free energy of the written domain state with respect to a uniformly polarized state.

Combining experiment and optical simulation in coherent X-ray nanobeam characterization of Si/SiGe semiconductor heterostructures

“…These methods provide insight into structural parameters of a wider range of heteroepitaxial materials and can be very broadly applied in cases where existing coherent diffraction methods cannot yet be applied. Beyond this Si/SiGe system and the relevant semiconducting materials, the simulation approach described here can be applied to other important heterostructures including complex oxides such as Pb(Zr,Ti)O 3 (PZT), 36 or ferroelectric superlattices 37 where the lattice strain distribution is one among different parameters which lead to the formation of exotic polarization domains. 38 Other coherent diffraction analysis methods, including phase retrieval methods such as coherent diffraction imaging or ptychography, have so far been based on the analysis of well-defined isolated reciprocal-space distributions of the scattered x-ray intensity.…”

Imaging Local Polarization in Ferroelectric Thin Films by Coherent X-Ray Bragg Projection Ptychography

“…3(e) in terms of amplitude |F 002 | and phase ∠F 002 , taking into account energy-dependent anomalous scattering contributions. For oppositely polarized domains with equal polarization magnitudes |P |, the structure factor magnitudes are nearly equivalent at 9.5 keV [32,33], whereas the phases differ by as much as 1.5 radians. Thus, a mostly uniform amplitude is expected in the BPP reconstruction with stripes of alternating phase ∠F 002 .…”

Preface to Special Topic: Selected Papers from the Piezoresponse Force Microscopy Workshop Series: Part of the Joint ISAF-ECAPD-PFM 2012 Conference

“…Guo et al 67 report the detailed studies of temperatureinduced evolution of structure and electromechanical response in ferroelectric polymer, and Shur et al 68 and Rodrigiez et al communicate their findings of light-induced photochemical reactivity on the ferroelectric LiNbO 3 surfaces, 69 providing new insight into physics and electrochemistry of ferroelectric-semiconductors. [33][34][35] The role of surface humidity of surface potential was explored by Verdaguer, 70 complementing earlier data on BaTiO 3 surfaces. [36][37][38][39][40] Several studies combine PFM and other localized characterizations, such as atomic force acoustic microscopy (AFAM) 41,42 by Zhou and Li et al, 71 and confocal Raman microscopy 72 and Raman spectroscopy.…”