Switchable thin film

Recently, ferroelectric materials, especially in thin film form, have attracted the attention of many researchers. Their large dielectric constants make them suitable as dielectric layers of microcapacitors in microelectronics. They are also investigated for application in nonvolatile memory using the switchable dielectric polarization of ferroelectric material. To characterize such ferroelectric materials, a high-resolution tool is required for observing the microscopic distribution of remanent (or spontaneous) polarization of ferroelectric materials. 

The methods of synthesis, the spectral and photochromic properties in solution, in polymer film and in vacuum-deposited thin films, and the structural determinations by X-ray diffraction are reviewed as is the electrochemical behavior of this family of switchable materials. 

One of the most important aspects of the discovery of switchable mirrors is the fact that in the form of thin films rare-earth hydrides (REH ) are amenable to a whole series of experiments, which were often impossible with bulk samples since hydrogen absorption resulted in a total disintegration of bulk samples. 

Only at 300 MPa is hep SCH3 formed [244]. Giebels et al. [179] confirmed the formation of SCH3 recently in thin films of Mg-Sc. These films become very transparent when the Mg content is larger than 65 at.%. They behave as Mg-Y and Mg-La switchable mirrors, that is they show a black state and a shift of the band gap with excess Mg. As Sc is a very expensive material, successful attempts have been made to substitute it with Ti, V and Cr [246]. 

The existence of ferroelectric phase in sufficiently thin antiferroelectric films had been revealed experimentally in several works [64-66]. In Ref. [64], the switchable ferroelectric polarization has been observed in PbZrOs antiferroelectric thin film on Si substrate. It has been revealed, that both in the latter film and in one more antiferroelectric BiNb04 one, the ferroelectric phase appears only if the film thickness is smaller then certain threshold value, which depends on material parameters. For instance, the ferroelectric hysteresis loop has been observed [65] in 100 nm thick PbZrOs/Si Alms, while those thicker than 400-500 nm revealed antiferroelectric behavior. Note, that the other primary ferroic demonstrates the same behavior. Namely, the films of antiferromagnetic BiFeOs on SrTiOs substrate reveal the emergence of ferromagnetism at the thicknesses less than 100 nm [67]. 

Colla, E.L., Taylor, D.V., Tagantsev, A.K., and Setter, N. (1998) Discrimination between bulk and interface scenarios for the suppression of the switchable polarization (fatigue) in Pb(Zr,Ti)03 thin film capacitors with Pt electrodes. Appl. Phys. Lett., 72 (19), 2478-2480. 

J. Peng, Y. Xnan, H.F. Wang, Y.M. Yang, B.Y. Li, Y.C. Han, Solvent-induced microphase separation in diblock copolymer thin films with reversibly switchable morphology, Journal of Chemical Physics 120 (2004) 11163-11170. 

G. Caputo, R. Cingolani, P.D. Cozzoli, A. Athanassiou, Wettability conversion of colloidal Ti02 nanocrystal thin films with UV-switchable hydrophilicity. PCCP 11, 3692-3700 (2009)... 

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