Nanoscale ferroelectric materials

Raman spectroscopy with ultraviolet excitation advantages and recent applications for nanoscale ferroelectric materials. 

Y. Rosenwaks, M. Molotski, A. Agronin, P. Urenski, M. Schvebelman, and G. Rosenman, Nanoscale characterization of ferroelectric materials. Scanning force microscopy approach, Eds. M. Alexe, A. Guverman, Springer, 2004. 

Ultraviolet Raman spectroscopy has emerged as a powerful technique for characterization of nanoscale materials, in particular, wide-bandgap semiconductors and dielectrics. The advantages of ultraviolet excitation for Raman measurements of ferroelectric thin films and heterostructures, such as reduced penetration depth and enhanced scattering intensity, are discussed. Recent results of application of ultraviolet Raman spectroscopy for studies of the lattice dynamics and phase transitions in nanoscale ferroelectric structures, such as superlattices based on BaTiOs, SrTiOs, and CaTiOs, as well as ultrathin films of BaTiOs and SrTi03 are reviewed. 

Size effect is another factor that strongly influences the properties of ferroelectric nanostructures, and the issue of a critical size for ferroelectricity has been actively discussed [4, 6, 11-14, 35]. For a long time it was believed that ferroelectricity was suppressed in small particles and thin films [1], and there was a critical size in order of few tens of nanometers below which a spontaneous polarization cannot be sustained in a material. Recent experimental and theoretical smdies [36 8] demonstrated that ferroelectricity exists down to vanishingly small sizes, much smaller than previously thought. These studies revealed that the issue of critical size is very complex, and electrical and mechanical boundary conditions play an essential role in nanoscale ferroelectricity. 

Nanoscale Characterisation of Ferroelectric Materials, Springer, Berlin. 

The major trends in ferroelectric photonic and electronic devices are based on development of materials with nanoscale features. Piezoelectric, electrooptic, nonlinear optical properties of fe are largely determined by the arrangement of ferroelectric domains. A promising way is a modification of these basic properties by means of tailoring nanodomain and refractive index superlattices. 

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