Raman studies of ferroelectric domain walls in lithium tantalate and niobate

Abstract

PACS 63.20.Dj, 77.84.Dy, 78.30.Hv Using confocal Raman spectroscopy at low temperature we investigated the perturbation of the phonon modes across a domain wall region as a function of sample stoichiometry in lithium tantalate and niobate. For all samples, we found that the Raman spectra were changed. The intensity of the A(LO) phonon modes and most of the E(TO) phonon modes were shifted and changed in their relative intensity over a 20 µm length scale. Our measurements suggest that the intensity of the A(LO) phonon modes change due to local charges induced by pyroelectric effect and/or photoionization, while the observed shifts are due to strains that are not relaxed in the domain wall region.

Influence of ferroelectric domain walls on the Raman scattering process in lithium tantalate and niobate

“…Previous work aimed at studying the properties of domain walls using Raman spectroscopy have shown intensity changes in the Raman spectrum [14-17] and frequency shifts of the bulk crystal Raman peaks in the Raman spectrum [15][16][17][18] near the domain wall. However, most of these effects are associated with intrinsic defects and local charging introduced by the nonstoichiometry of the samples.…”

Microscopic and Raman Spectroscopic Investigation of the Domain Structures in LiNbO3:Y:Mg Crystals

“…It can be assumed that the shift of the E(TO 8 ) band position found in refs. [15] and [16] is related to the growth of the E(TO 9 ) band.…”

“…Micro-Raman spectroscopy is recently applied to the investigation of the domain structure of PPLN or domain inverted crystals [15,16]. It was found that some parameters (e.g.…”

Terahertz plasmonics in ferroelectric-gated graphene

“…15 According to the Raman scattering data, 18,32,33 LiNbO 3 has two fundamental transverse optical-phonon frequencies x To and x Te , corresponding to the ordinary and extraordinary waves, respectively. The main behaviors of the permittivities o and e in the 0.1-10 THz frequency range can be fitted by the Lorentz model, 15,17 For plane waves, we set k y ¼ 0 without loss of generality, and explicitly derive k x as…”

“…In Table I, we list the calculated characteristic quantities at about 100 K. For sensitive THz-photon manipulation, a low temperature is helpful for suppressing the thermal noise or dissipation. 10,11,32,33 In Table I, one can see clearly the huge effective refractive index and ultra-short modal wavelength compared with the free-space wavelength of low-THz photons. Large dissipation occurs at frequencies above 4 THz; whereas below 4 THz, for E F Շ 0:1 eV, the wavelength can indeed be squeezed to 100-200 nm while the confining length is only about 10-20 nm.…”