Effect of Humidity on the Writing Speed and Domain Wall Dynamics of Ferroelectric Domains

The switching dynamics of ferroelectric polarization under electric fields depends on the availability of screening charges in order to stabilize the switched polarization. In ferroelectrics, thin films with exposed surfaces investigated by piezoresponse force microscopy (PFM), the main source of external screening charges is the atmosphere and the water neck, and therefore relative humidity (RH) plays a major role. Here, it is shown how the dynamic writing of domains in BaTiO3 thin films changes by varying scanning speeds in the range of RH between 2.5% and 60%. The measurements reveal that the critical speed for domain writing, which is defined as the highest speed at which electrical writing of a continuous stripe domain is possible, increases non-monotonically with RH. Additionally, the width of line domains shows a power law dependence on the writing speed, with a growth rate coefficient decreasing with RH. The size of the written domains at a constant speed as well as the creep-factor μ describing the domain wall kinetics follow the behavior of water adsorption represented by the adsorption isotherm, indicating that the screening mechanism dominating the switching dynamics is the thickness and the structure of adsorbed water structure and its associated dielectric constant and ionic mobility.The authors want to acknowledge technical support from I. Gaponenko on the installation of the low-noise humidity controller. Financial support was obtained under projects from the Spanish Ministerio de Ciencia e Innovacion (MICINN) under projects PID2019-108573GB-C21, PID2019-109931GB-I00, and PID2019-110907GB-I00. In addition, this work was partially funded by 2017-SGR-579 from the Generalitat de Catalunya. The ICN2 was funded by the CERCA programme / Generalitat de Catalunya. The ICN2 was supported by the Severo Ochoa Centres of Excellence Programme, funded by the Spanish Research Agency (AEI, Grant no. SEV-2017-0706). The ICMAB was supported by the “Severo Ochoa” Program for Centers of Excellence in R&D (CEX2019-000917-S). I.S. acknowledges support of the Secretaria d'Universitats i Recerca - Departament d'Empresa i Coneixement - Generalitat de Catalunya and the European Social Fund (ESF) (FI grant reference 2020 FI_B2 00157).Peer reviewe