Defect–Domain Wall Interactions in Trigonal Ferroelectrics

Gopalan, Venkatraman; Dierolf, Volkmar; Scrymgeour, David

doi:10.1146/annurev.matsci.37.052506.084247

Cited by 241 publications

(184 citation statements)

References 111 publications

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“…Furthermore, a linear thickness dependence of the voltage required for stable polarization switching from "up" to "down" state, V down , was measured while the voltage for polarization reversal to the original state, V up , remained approximately constant, which can be ascribed to large frozen defect fields. 38,60 In Mg:LN above buried PE phases, stable polarization reversal is prevented, which is in contrast to the observations in undoped LN. This effect is ascribed to the strong remaining frozen polarization in the PE phase of Mg:LN that counteracts switching and is greatly reduced in undoped LN.…”

Section: Discussioncontrasting

confidence: 79%

“…LN and the origin of frozen defect fields that favor the initial polarization orientation. 37,38 The strength of this defect field is estimated from the asymmetry in E up and E down as depicted in Figure 5(b) to be 2.34 6 0.47 kV/mm and shows no thickness dependence. While in undoped congruent LN, internal defect fields of this order of magnitude are expected, fields of only %0.5 kV/mm are reported for Mg:LN as high concentration doping leads to a reduction in vacancies.…”

Section: B Thickness Dependence Of Ferroelectric Switchingmentioning

confidence: 99%

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Interface and thickness dependent domain switching and stability in Mg doped lithium niobate

Neumayer

Ivanov

Manzo

et al. 2015

Journal of Applied Physics

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Controlling ferroelectric switching in Mg doped lithium niobate (Mg:LN) is of fundamental importance for optical device and domain wall electronics applications that require precise domain patterns. Stable ferroelectric switching has been previously observed in undoped LN layers above proton exchanged (PE) phases that exhibit reduced polarization, whereas PE layers have been found to inhibit lateral domain growth. Here, Mg doping, which is known to significantly alter ferroelectric switching properties including coercive field and switching currents, is shown to inhibit domain nucleation and stability in Mg:LN above buried PE phases that allow for precise ferroelectric patterning via domain growth control. Furthermore, piezoresponse force microscopy (PFM) and switching spectroscopy PFM reveal that the voltage at which polarization switches from the "up" to the "down" state increases with increasing thickness in pure Mg:LN, whereas the voltage required for stable back switching to the original "up" state does not exhibit this thickness dependence. This behavior is consistent with the presence of an internal frozen defect field. The inhibition of domain nucleation above PE interfaces, observed in this study, is a phenomenon that occurs in Mg:LN but not in undoped samples and is mainly ascribed to a remaining frozen polarization in the PE phase that opposes polarization reversal. This reduced frozen depolarization field in the PE phase also influences the depolarization field of the Mg:LN layer above due to the presence of uncompensated polarization charge at the PE-Mg:LN boundary. These alterations in internal electric fields within the sample cause long-range lattice distortions in Mg:LN via electromechanical coupling, which were corroborated with complimentary Raman measurements. V C 2015 AIP Publishing LLC. [http://dx

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Section: Discussioncontrasting

confidence: 79%

Section: B Thickness Dependence Of Ferroelectric Switchingmentioning

confidence: 99%

Interface and thickness dependent domain switching and stability in Mg doped lithium niobate

Neumayer

Ivanov

Manzo

et al. 2015

Journal of Applied Physics

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“…30 As described by Gopalan et al, upon poling, the Nb Li antisites show the same behavior as Li ions and move through the oxygen plane to the second thermodynamically stable position in the neighboring octahedron. 31 However, due to the low mobility of Li þ at room temperature, 32 the positions of the V Li remain the same, leaving the polar orientation of the defect cluster in the poled region in a frustrated state. There is, therefore, an asymmetry in the internal electric fields for oppositely poled domains, whereby the parallel depolarization and defect fields in the a)…”

Section: Introductionmentioning

confidence: 99%

Influence of annealing on the photodeposition of silver on periodically poled lithium niobate

Carville

Neumayer

Manzo

et al. 2016

Journal of Applied Physics

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The preferential deposition of metal nanoparticles onto periodically poled lithium niobate surfaces, whereby photogenerated electrons accumulate in accordance with local electric fields and reduce metal ions from solution, is known to depend on the intensity and wavelength of the illumination and the concentration of the solution used. Here, it is shown that for identical deposition conditions (wavelength, intensity, concentration), post-poling annealing for 10 h at 200 C modifies the surface reactivity through the reorientation of internal defect fields. Whereas silver nanoparticles deposit preferentially on the þz domains on unannealed crystals, the deposition occurs preferentially along 180 domain walls for annealed crystals. In neither case is the deposition selective; limited deposition occurs also on the unannealed -z domain surface and on both annealed domain surfaces. The observed behavior is attributed to a relaxation of the poling-induced defect frustration mediated by Li þ ion mobility during annealing, which affects the accumulation of electrons, thereby changing the surface reactivity. The evolution of the defect field with temperature is corroborated using Raman spectroscopy. V C 2016 AIP Publishing LLC. [http://dx

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“…An explanation for the experimentally observed enhancement of the RI contrast can be provided by a RI discontinuity which occurs on the domain boundary as reported in Ref. 15. According to this report the RI changes abruptly in the vicinity of the domain boundary.…”

mentioning

confidence: 54%

Poling-inhibited ridge waveguides in lithium niobate crystals

Sones

Ganguly

Ying

et al. 2010

Applied Physics Letters

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Ultraviolet laser irradiation of a lithium niobate +z polar surface enables the production of ridge waveguides. Ultraviolet laser induced inhibition of poling is used to define an inverted domain pattern which transforms into a ridge structure by differential etching in Hydrofluoric acid. The laser irradiation step also induces a refractive index change that provides the vertical confinement within the ridge structure. Furthermore, it was observed that poling-inhibition results in a significant enhancement of the refractive index contrast between the bulk crystal and the ultraviolet irradiated tracks.Lithium niobate (LN) because of its distinctive combination of inherent physical properties; has always been recognised as an appropriate platform for implementation of integrated optical circuits 1 . One of the suggested approaches which is quite regularly implemented to further improve the efficiency and compactness of such integrated optical circuits based on components such as modulators and resonators, is the use of ridge waveguides instead of conventional diffused 2 or proton-exchanged 3 waveguides. Such ridge waveguide superstructures provide better lateral confinement of the optical mode due to the much higher index contrast as compared to their conventional counterparts. Several different methods have been investigated for the production of ridge waveguides in LN. Most of them utilize an etching step that defines the ridge geometry and a separate waveguide fabrication step 4-6 such as the commonly used ionindiffusion or proton-exchange processes. Delineation of the ridge is achieved either via wet etching in an acid mixture containing hydrofluoric acid (HF) or through dry etching processes such as ion beam milling 7 or plasma etching 8 . Domain-selective acid-based wet etching has also been reported as an alternative approach for defining ridges in domain engineered LN 9 . Interestingly, ridge waveguides have also been fabricated by mechanical dicing of planar MgO:LN bonded on to LN 10 . The mandatory step required to induce the vertical refractive index (RI) contrast either precedes or succeeds the wet or dry etching process. In all of these approaches, a clean-room based photolithographic step is incorporated to define the ridge on an already produced planar waveguide or to define the waveguide on a prestructured ridge. Any alternative process that reduces the complexity of fabrication would be extremely well-suited for the implementation of the dense compact photonic circuits envisaged for future optoelectronic integration technologies. In this contribution we report on such an alternative method for the fabrication of ridge waveguides in z-cut LN. The method utilizes a continuous wave (c.w.) UV laser direct writing procedure that provides both the definition of the ridge pattern and the production of the necessary RI contrast for vertical confinement in a single step. Direct writing (DW) of waveguides in congruent LN has been demonstrated using c.w. UV laser light with writing wavelengths within the ran...

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Defect–Domain Wall Interactions in Trigonal Ferroelectrics

Cited by 241 publications

References 111 publications

Interface and thickness dependent domain switching and stability in Mg doped lithium niobate

Interface and thickness dependent domain switching and stability in Mg doped lithium niobate

Influence of annealing on the photodeposition of silver on periodically poled lithium niobate

Poling-inhibited ridge waveguides in lithium niobate crystals

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