At the most basic level, SPM imaging has been used in order to locate areas of interest for coarser resolution micro-Raman measurements, enabling a better understanding of the resulting signal from the qualitative model of the underlying domain structrures 17. Indeed, such multi-technique studies have already been leveraged at varying length scales and with a varying degree of correlation.
Whilst most of these investigations were carried out using a combination of high resolution scanning probe microscopy (SPM) based techniques 11 to explore the electromechanical and electrochemical responses, optical approaches-in particular second harmonic generation (SHG) microscopy with polarimetry analysis-are increasingly being used as a way to non-invasively probe the internal structure, chirality and polarization of domain walls 12, 13, 14, 15, 16.Ĭombining the two felicitously complementary techniques-with sequential SPM and SHG measurements of the same intrinsic or engineered domain structure-provides an opportunity to extract a complete structural and functional portrait of domain walls. Recently, the focus has shifted towards the investigation of ferroelectric domains and domain walls-interfaces separating regions of differing polarization orientation-as their intrinsically nanoscale nature and unique functional properties make them potentially useful for device applications 5, 6.Įver more detailed studies have revealed unusual behaviours such as localized electrical conduction 7, 8, mechanical shear 9 or magnetic ordering closely tied to the distinct structure of domain walls 10. They possess a spontaneous polarization switchable under the application of an electric field, and a wealth of associated functional properties including strong nonlinear electro-optical effects, very high piezo- and pyroelectric responses, and in some cases magnetoelectric coupling 4. Among these materials, ferroelectrics are of particular interest. In the last decades, complex oxide materials have shown promise in photovoltaics applications 1, high efficiency actuation and sensing 2, as well as information storage 3. Technological advances rely heavily on the development of new materials, both in terms of understanding their fundamental properties and through the engineering of their composition and structure.
DIFFERENT DATA ANALYSIS METHODS MANUAL
When applied to a data set containing scanning probe microscopy piezoresponse and second harmonic generation polarimetry measurements, our workflow reveals behaviours that could not be seen by usual manual analysis, and the origin of which is only explainable by using the quantitative correlation between the two data sets.
The method, based on a combination of data stacking, distortion correction, and machine learning, enables a precise mesoscale analysis.
Here, we propose a fast and unbiased analysis method for heterogeneous spatial data sets, enabling quantitative correlative multi-technique studies of functional materials. However, due to the different nature of the characterization methods, only limited and indirect correlation has been achieved between them, even when the same spatial areas were probed. In ferroelectrics, for instance, scanning probe microscopy based techniques have been used in conjunction with advanced optical methods to probe the structure and properties of nanoscale domain walls, revealing complex behaviours such as chirality, electronic conduction or localised modulation of mechanical response. The wealth of properties in functional materials at the nanoscale has attracted tremendous interest over the last decades, spurring the development of ever more precise and ingenious characterization techniques.