  It was discovered in 2010 that Croconic Acid, in its crystal form, has the
highest polarization among organic ferroelectrics. In the context of
eliminating toxic substances from electronic devices, Croconic Acid has a great
potential as a sublimable lead-free ferroelectric. However, studies on
ferroelectric properties of its thin films are only in their early stages and
its capability to be incorporated in nanoscale devices is unknown. In this
work, we demonstrate, upon ferroelectric switching at the nanoscale, stable and
enduring room temperature polarization with no leakage current in Croconic Acid
thin films. We thus show that it is a promising lead-free organic ferroelectric
toward integration in nanoscale devices. The challenging switching current and
polarization reversal characterization at the nanoscale was done using a unique
combination of piezoresponse force microscopy, polarization switching current
spectroscopy and the concurrent electromechanical strain response. Indeed, this
combination can help to rationalize otherwise asymmetric polarization-voltage
data and distorted hysteresis due to current jumps below the background noise,
which are statistically washed away in macrojunctions but become prevalent at
the nanoscale. These results are valid irrespective of the ferroelectrics'
nature, organic or inorganic. Beyond the potential of Croconic Acid as an
ecological ferroelectric material in devices, our detection of a clear
nanoscopic polarization switching current thus paves the way for a fundamental
understanding and technological applications of the polarization reversal
mechanism at the nanoscale.
