Bratkovsky AM, Levanyuk AP
Hewlett-Packard Laboratories, 1501 Page Mill Road, Palo Alto, California 94304, USA.
Phys Rev Lett. 2000 Nov 20;85(21):4614-7. doi: 10.1103/PhysRevLett.85.4614.
The actual mechanism of polarization switching in ferroelectrics remains a puzzle for many decades, since the usually estimated barrier for nucleation and growth is insurmountable ("paradox of the coercive field"). To analyze the mechanisms of the nucleation we consider the exactly solvable case of a ferroelectric film with a "dead" layer at the interface with electrodes. The classical nucleation is easier in this case but still impossible, since the calculated barrier is huge. We have found that the interaction between the nuclei is, however, long range, hence one has to study an ensemble of the nuclei. We show that there are ensembles of small (embryonic) nuclei that grow without the barrier. We submit that the interaction between nuclei is the key point for solving the paradox.
几十年来，铁电体中极化切换的实际机制一直是个谜，因为通常估算的成核和生长势垒是无法逾越的（“矫顽场悖论”）。为了分析成核机制，我们考虑了铁电薄膜在与电极界面处存在“死层”这一可精确求解的情况。在这种情况下，经典成核更容易发生，但仍然不可能，因为计算出的势垒非常大。然而，我们发现核之间的相互作用是长程的，因此必须研究核的集合。我们表明，存在一些小（胚胎）核的集合，它们在没有势垒的情况下生长。我们认为核之间的相互作用是解决这一悖论的关键。
