Probing local electromechanical effects in highly conductive electrolytes
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Depending on the ionic concentration of a liquid electrolyte droplet around a biased scanning probe microscopy tip, ferroelectric domains can be excited locally underneath the tip (left) or globally across the liquid droplet (right).
Electromechanical imaging of ferroelectric domains using Scanning Probe Microscopy (SPM) has been achieved in a liquid with high ionic strength. Electromechanical phenomena are characteristic of materials ranging from ferroelectrics to ionic systems such as batteries and supercapacitors, to biological systems that often require a liquid environment for stability and functionality. However, the electrical conductivity of the typically used liquids alters the electrical field applied to the scanning probe and could limit the use of electromechanical charcterization techniques in these liquids. By imaging ferroelectric domains of BiFeO
in Na
SO
solutions with increasing ionic strength and comparing the results to numerical modeling it is shown1 that the electric field around an ac-biased SPM tip is localized for low conductivity liquids and becomes global for higher conductivities. Therefore, the excitation can be tuned from local to global by changing the conductivity of the liquid. At the same time, the detection of the electromechanical signal remains local. This work will open pathways to SPM techniques in liquids with high ionic strength, which is not only important for ferroelectrics but also for battery materials and other electrochemical studies.
Nina Balke, Alexander Tselev, Thomas M. Arruda, Stephen Jesse, Ying-Hao Chu, and Sergei V. Kalinin, “Probing Local Electromechanical Effects in Highly Conductive Electrolytes,” ACS Nano, DOI: 10.1021/nn3038868 (2012).
