Mechanical-Induced Polarization Switching in Relaxor Ferroelectric Single Crystals

Abstract

Control of coupling between electric and elastic orders in ferroelectric bulks is vital to understand their nature and enrich the multifunctionality of polarization manipulation applied in domain-based electronic devices such as ferroelectric memories and data storage ones. Herein, taking (1 – x%)­Pb­(Mg1/3Nb2/3)­O3–x%PbTiO3 (PMN–x%PT, x = 32, 40) as the prototype, we demonstrate the less-explored mechanical switching in relaxor ferroelectric single crystals using scanning probe microscopy. Low mechanical forces can induce metastable and electrically erasable polarization reversal clearly from electrical-created bipolar domains around the 180° domain wall in monoclinic PMN–32%PT and inside the c+ domain in tetragonal PMN–40%PT. The mechanical switching evolutions show force/time dependence and time-force equivalence. The time-dependent mechanical switching behavior stems from the participation and contribution of polar nanoregions. Flexoelectricity and bulk Vegard strain effect can account for the mechanical switching but notably, the former in the two has very different origins. These investigations exhibit the possibility of mechanical switching as a tool to manipulate polarization states in ferroelectric bulks, and provide the potential of these crystals as substrates in mechanical polarization control of future thin-film devices.

Low‐Pressure Mechanical Switching of Ferroelectric Domains in PbZr0.48Ti0.52O3

“…Mechanical switching has been reported in a range of ferroelectric materials from single crystals (BaTiO 3 , [ 18 ] (1 − x )Pb(Mg 1/3 Nb 2/3 )O 3 − x PbTiO 3 ( x = 0.32, 0.40) [ 19 ] ) to thin films (Pb(Zr 0.2 Ti 0.8 )O 3 , [ 20 , 21 ] BaTiO 3 , [ 1 , 22 ] BiFeO 3 [ 23–25 ] ). Among these, Pb(Zr 0.2 Ti 0.8 )O 3 thin films have shown promising mechanical switching properties with anticipated memory storage capacities of the order of 110 Gb cm −3 reported using atomic force microscope (AFM) tip forces down to 300 nN.…”

Mechanical Manipulation of Nano‐Twinned Ferroelectric Domain Structures for Multilevel Data Storage

“…Since 180° polarization switching was accomplished in 4.8 nm thick tetragonal BaTiO 3 thin films via mechanical manipulation, [ 25 ] considerable effort has been devoted to manipulating the polarization switching in ferroelectric thin films, for example, 3–5 nm thick PbZr 0.2 Ti 0.8 O 3 (001) film, 1.6–45 nm thick BaTiO 3 (001) film, 50 nm thick PbZr 0.1 Ti 0.9 O 3 (001) film, and 10 nm thick PbZr 0.48 Ti 0.52 O 3 (001) film, and flexoelectric effect is proposed to explain the mechanical manipulation of the domain and domain wall structures. [ 25–40 ] It is accepted that using tip force turns to be an effective alternative to electric field for switching ferroelectric domains. [ 32–40 ] However, mechanical manipulation based on flexoelectricity has proved ineffective when going beyond a critical thickness (tens of nanometers), [ 40 ] because tip induced flexoelectricity is usually negligible in thick films due to the small strain gradient, and the flexoelectricity in thin films substantially decreases when the film thickness is above a certain thickness.…”

“…[ 25–40 ] It is accepted that using tip force turns to be an effective alternative to electric field for switching ferroelectric domains. [ 32–40 ] However, mechanical manipulation based on flexoelectricity has proved ineffective when going beyond a critical thickness (tens of nanometers), [ 40 ] because tip induced flexoelectricity is usually negligible in thick films due to the small strain gradient, and the flexoelectricity in thin films substantially decreases when the film thickness is above a certain thickness. [ 40 ] Interestingly, Chen et al.…”

Optomechanical Mapping of Ferroelectric Domains and the Piezo‐Photovoltaic Effect in Ba‐ and Ni‐Doped (K0.5Na0.5)NbO3

“…Nadupalli et al [ 11 ] named it piezo‐photovoltaic effect (ferroelectric analogy of the flexo‐photovoltaic effect where mechanical strain disturbs the material symmetry leading to a temporary or permanent change in the state of polarization) which should not be confused with the piezo‐phototronic effect [ 13 ] (“ change in Schottky barrier height due to generation of piezoelectric charges ” [ 11 ] ). Mechanical force‐induced manipulation of ferroelectric domains has been independently and extensively studied in ferroelectric single crystals, [ 14,15 ] and thin films. [ 16,17 ] The prime reasons for the mechanical switching in ferroelectric domains can either be due to one of the following mechanisms or by the cumulative effect of 1) pure mechanical loading, [ 18 ] 2) flexoelectric effect, [ 17,19 ] and 3) ferroelectric–ferroelastic switching.…”