Effect Of Domain Boundaries Research Articles

Nanoscale ferroelectric switching behavior at charged domain boundaries studied by angle-resolved piezoresponse force microscopy

We investigated the effect of charged domain boundaries (CDBs) on the coercive voltage (Vc) in polycrystalline Pb(Zr0.25Ti0.75)O3 (PZT) thin films using angle-resolved piezoresponse force microscopy (AR-PFM). By using the AR-PFM technique, we could observe the detailed domain structure with various degrees of CDBs including neutral domain boundaries in the PZT thin films. We found that the Vc increases at CDBs induced by polarization discontinuities. We attribute the change in Vc to the built-in field created by uncompensated polarization charges at the CDBs in the PZT thin films.

Initial Stages of High-Temperature CaF<SUB>2</SUB>/Si(001) Epitaxial Growth Studied by Surface X-Ray Diffraction

Surface X-ray diffraction was applied to study structure of the fluorite-silicon interface forming upon epitaxial growth of CaF2 on Si(001) surface kept at 750 degrees C. Samples with CaF2 coverage of 1.5-4 (110)-monolayers were grown and in-situ characterized using synchrotron radiation. The 3 x 1-like surface reconstruction was observed in agreement with the previous studies by electron diffraction. Interestingly, a well pronounced splitting of the fractional x 1/3 reflections was revealed. This splitting was ascribed to the effect of antiphase domain boundaries in the row-like structure of the interface layer. The in-plane integrated intensities were used to reconstruct two-dimensional atomic structure of the high-temperature CaF2/Si(001) interface.

Effects of the antiferromagnetic anti-phase domain boundary on the magnetization processes in Ni 2Mn(Ga 0.5Al 0.5) Heusler alloy

The effects of anti-phase domain (APD) boundaries on the magnetic properties of Ni2Mn(Ga0.5Al0.5) alloy were studied by magnetic measurements and transmission electron microscopic observations. The growth of APDs at 773 K followed the square root law for annealing time. While the saturation magnetization and the Curie temperature were hardly affected by the APD size, the magnetization curve in the specimen with smaller mean APD size became harder, caused by the pinning effect of the magnetic domain walls due to the APD boundaries.

The interaction between contrast, prosody, and coarticulation in structuring phonetic variability

Russian maintains a contrast between non-palatalized and palatalized trills that has been lost in most Slavic languages. This research investigates the phonetic expression of this contrast in an attempt to understand how the contrast is maintained. One hypothesis is that the contrast is stabilized through resistance to coarticulation between the trill and surrounding vowels and prosodic positional weakening effects—factors expected to weaken the contrast. In order to test this hypothesis, we investigate intrasegmental and intersegmental coarticulation and the effect of domain boundaries on Russian trills. Since trills are highly demanding articulatorily and aerodynamically, and since Russian trills are in contrast, there is an expectation that they will be highly resistant to coarticulation and to prosodic influence. This study shows, however, that phonetic variability due to domain boundaries and coarticulation is systematically present in Russian trills. Implications of the relation between prosodic position and lingual coarticulation for the Degree of Articulatory Constraint (DAC) model, Articulatory Phonology, and the literature on prosodic strength are discussed. Based on the quantitative analysis of phonetic variability in Russian trills, we conjecture a hypothesis on why the contrast in trills is maintained in Russian, but lost in other Slavic languages. Specifically, phonological strategies used by several Slavic languages to deal with the instability of Proto-Slavic palatalized trills are present phonetically in Russian. These phonetic tendencies structure the variability of Russian trills, and could be the source of contrast stabilization.

Intrinsic damping, relaxation processes, and internal friction in vibrating systems.

Vibrations lose energy because of (1) coupling of the system to other systems or to the environment or of (2) intrinsic damping within the system itself. The present paper attempts to survey the current state of understanding for the principal mechanisms of the latter type with explicit physics (rather than purely phenomenological considerations), as simply as practical. Some mechanisms are evidenced in the attenuation of waves in unbounded homogeneous media, others are caused by the presence of boundaries. Some explicitly require quantum-mechanical concepts for their explanation, others can be explained in terms of classical mechanics and thermodynamics. Specific mechanisms that are to be discussed include those associated with thermal conductivity, grain and domain boundary effects, interstitial atom diffusion, relaxation by diffusion, inter-grain diffusion, micro-eddy current losses, hysteresis losses, thermoelastic internal friction, thermal damping associated with transverse vibrations of thin bodies, phonon-phonon interactions, phonon-electron interactions, internal fluids, and dislocations. The concept of relaxation often provides a convenient unified description. Rather than use the local averaged particle displacement as a sole description of the local vibrations, one considers additional local variables, loosely referred to as hidden variables. Each such variable, when disturbed, relaxes to its equilibrium value with a characteristic relaxation time.

Self-assembled monolayer and multilayer formation using redox-active Ru complex with phosphonic acids on silicon oxide surface

The formation of self-assembled monolayer and multilayer using redox-active Ru complex molecules with phosphonic acids on SiO 2 surface has been examined using X-ray photoelectron spectroscopy (XPS), ellipsometry, and time of flight secondary mass-ion spectroscopy (TOF-SIMS). We found that an introduction of a Zr adlayer leads to higher surface molecular density of Ru complex SAMs on the SiO 2 surface, compared to that of obtained from the direct adsorption of Ru complex monolayer on the SiO 2 surface. We further tried to fabricate a multilayer film using this molecule with Zr(IV) ion acting as a chemical glue by a successive immersion process. The XPS data revealed that the molecular densities of the multilayers were also higher for the immobilization with Zr adlayer between Ru complex and SiO 2 surface than those without the Zr adlayer, suggesting that Zr adlayer is effective in forming highly packed molecular layer of phosphonic acids on SiO 2 surface. We found the film growth reached a saturation point after 6 layers on the SiO 2 surface. The film growth saturation can be explained by a molecular domain boundary effect encountered due to the large tilt angle of the molecular layer.

Effect of domain boundaries on the electrical properties of crystalline Gd2O3 thin films

We report on the effect of domain boundaries on the electrical properties of epitaxial Gd2O3 thin films grown on Si(001) substrates with 4° miscut along [110] azimuth. Dedicated preparation of the substrate surfaces can lead to two different microstructures of epitaxial Gd2O3 layers when grown at identical growth conditions. A substrate surface with terraces of biatomic steps height is the key point to achieve single crystalline epitaxial Gd2O3 layer. Such epi-Gd2O3 layers exhibited significantly lower leakage currents compared with the commonly obtained epitaxial layers with two orthogonal domains. However, for capacitance equivalent thickness below 1 nm, this difference disappears, indicating that for ultrathin layers direct tunneling becomes dominating. Additionally, forming gas annealing can reduce the leakage current by a few orders of magnitude. Here, thinner layers of both structural types exhibited similar electrical properties.

DIFFUSION LENGTH AND EFFECTIVE CARRIER LIFETIME IN III-NITRIDES

The results of excess carrier diffusion length investigations in GaN and in the light emitting structures (LES) based on MQW InGaN / GaN with different ordering of mosaic structures are presented. It is confirmed that the diffusion length values in these structures indeed are essentially lower than 1 μm. The Electron Beam Induced Current investigations have shown that the effective diffusion length measured on GaN structures could be determined by the mosaic domain boundary effect on the excess carrier transport. Such nanosize domains could also determine the lateral localization in the MQW light emitting diodes. The mosaic structure ordering effect on the quantum efficiency of LES and high values of the effective carrier lifetime in well-ordered LES are discussed.

Dielectric abnormities in BaTi0.9(Ni1∕2W1∕2)0.1O3 giant dielectric constant ceramics

Ba Ti 0.9 ( Ni 1 ∕ 2 W 1 ∕ 2 ) 0.1 O 3 ceramics were fabricated and their dielectric properties were investigated. With the sintering temperature increasing from 1250to1280°C, the grain size abruptly increases from 1–2to20–40μm, accompanying significant changes in dielectric response. The samples with larger grains exhibit giant dielectric constant characteristics, which are considered to be mainly attributed to the domain boundary effect. The activation energies of the dielectric relaxation Erelax=0.325eV reveal the existence of microdomains in larger grains. The ac conductivity results also give the evidence of the domain boundary effect in the present ceramics.

Mathematical analysis of the optimal habitat configurations for species persistence

We study a reaction–diffusion model in a binary environment made of habitat and non-habitat regions. Environmental heterogeneity is expressed through the species intrinsic growth rate coefficient. It was known that, for a fixed habitat abundance, species survival depends on habitat arrangements. Our goal is to describe the spatial configurations of habitat that maximise the chances of survival. Through numerical computations, we find that they are of two main types – ball-shaped or stripe-shaped. We formally prove that these optimal shapes depend on the habitat abundance and on the amplitude of the growth rate coefficient. We deduce from these observations that the optimal shape of the habitat realises a compromise between reducing the detrimental habitat edge effects and taking advantage of the domain boundary effects. In the case of an infinite-periodic environment, we prove that the optimal habitat shapes can be deduced from those in the case of a bounded domain.

Ac conductivity relaxation processes in CaCu3Ti4O12 ceramics: Grain boundary and domain boundary effects

The ac conductivity of CaCu3Ti4O12 ceramics associated with electrical charge carrier motion (ions or vacancies) was investigated as a function of frequency at different temperatures. The long range migration of charge carriers within the ceramic is restricted by two kinds of insulating barriers, namely, grain boundaries and domain boundaries. The potential barriers associated with these boundaries lead to two anomalies in conductivity response and three frequency-dependent contributions to conductivity: long range diffusion of carriers, carrier migration localized within grains, and carrier migration localized within domains.

Exclusion of a transmembrane-type peptide from ordered-lipid domains (rafts) detected by fluorescence quenching: extension of quenching analysis to account for the effects of domain size and domain boundaries.

Sphingolipid/cholesterol-rich rafts are membrane domains thought to exist in the liquid-ordered state. To understand the rules governing the association of proteins with rafts, the behavior of a model membrane-inserted hydrophobic polypeptide (LW peptide, acetyl-K(2)W(2)L(8)AL(8)W(2)K(2)-amide) was examined. The distribution of LW peptide between coexisting ordered and disordered lipid domains was probed by measuring the amount of LW Trp fluorescence quenched by a nitroxide-labeled phospholipid that concentrated in disordered lipid domains. Strong quenching of the Trp fluorescence (relative to quenching in model membranes lacking domains) showed that LW peptide was concentrated in quencher-rich disordered domains and was largely excluded from ordered domains. Exclusion of LW peptide from the ordered domains was observed both in the absence and in the presence of 25-33 mol % cholesterol, indicating that the peptide is relatively excluded both from gel-state domains (which form in the absence of cholesterol) and from liquid-ordered-state domains (which form at high cholesterol concentrations). Because exclusion was also observed when ordered domains contained sphingomyelin in place of DPPC, or ergosterol in place of cholesterol, it appeared that this behavior was not strongly dependent on lipid structure. In both the absence and the presence of 25 mol % cholesterol, exclusion was also not strongly dependent upon the fraction of the bilayer in the form of ordered domains. To evaluate LW peptide behavior in more detail, an analysis of the effects of domain size and edges upon quenching was formulated. This analysis showed that quenching can be affected both by domain size and by whether a fluorescent molecule localized at domain edges. Its application to the quenching of LW peptide indicated that the peptide did not preferentially reside at the boundaries between ordered and disordered domains.

Quantity estimations by groups and individuals: Effects of known domain boundaries.

Quantity estimations by groups and individuals: Effects of known domain boundaries.

Microstructure of La1–xCaxMnO3 studied by transmission electron microscopy

Microstructures of La1-xCaxMnO3 compounds (x = ⅓ and 0.5) prepared with and without intermediate grinding were studied using transmission electron microscopy. A high density of antiphase boundaries (APBs) with displacement vector 1/2 〈111〉, indexed in orthorhombic unit cell, has been observed in bulk samples with no or minimum intermediate grinding. The nature of this APB is analyzed and found to bedue to the symmetry breaking introduced by the tilting of MnO6 octahedra relative to the ideal perovskite structure. Samples prepared using two intermediate grinds do not show these defects indicating that the microstructure can be controlled through synthesis routes. The effect of domain boundaries on the colossal magnetoresistance effect is discussed.

Prosodic domain effects on noninitial syllables

Previous literature has documented strengthening of segments adjacent to prosodic domain boundaries. This strengthening might be expected to affect only the segment next to the boundary. Yet, Fougeron and Keating [J. Acoust. Soc. Am. 101, 3728–3740 (1997)] found that some noninitial vowels showed strengthening in a domain-initial syllable, as did some onset consonants in final syllables. To test whether effects of prosodic domain boundaries extend beyond the domain-adjacent syllable, consonant and vowel durations were measured for the second, stressed, syllable in the place names Apollo, Atami, and Acosta, comparing utterance-, intonation phrase- and word-initial position. Results for four female and one male speaker indicate that while there is rarely any effect on the consonant, the stressed vowel in the nonboundary adjacent syllable shows domain effects in more than half of the items tested, with longer durations in higher domains, particularly in Atami. These surprising nonlocal effects suggest that: (1) the place of articulation effect may be due to simple distance from the boundary, since [t]s were usually shorter than the other consonants; and (2) domain edge strengthening may involve a change in articulatory setting, the onset of which is controlled more carefully than the offset. [Work supported by NSF SBR9600930.]

Effect of Domain Boundary on Carrier Transport of Calamitic Liquid Crystalline Photoconductive Materials

Smectic mesophases in the calamitic liquid crystalline materials such as 2-phenylnaphthalene derivatives exhibit fast ambipolar carrier transport, whose mobility is up to 10−2 cm2/Vs. For these mesophases, we have investigated the effect of defects in the bulk and at the domain boundary on these carrier transport by measuring transient photocurrents in thick cells up to 120 μm in thickness and in the cells of different domain sizes of 10–100s μm. It was found that non-dispersive carrier transports was observed for all the cells and the carrier transport was affected neither by cell thickness nor by domain sizes. Thus, it was concluded that there are few deep defects in the bulk and that the domain boundary is electrically inactive in these mesophases, demonstrating their high potential for practical application to large-area electronic devices.

Effect of domain boundary on the electrical conductivity of a magnetic nanocontact

The conductivity of a magnetic nanocontact with a spin inhomogeneity in the form of a Ginzburg-Bulaevski\(\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{l}\) domain wall at the center between oppositely magnetized edges is considered. The conductivity of the nanocontact is calculated in the ballistic approximation for Fe, Co, and Ni in the low-temperature limit, with allowance made for the spatial major-minor change in the electron spin energy due to exchange splitting in the edges. The calculations are carried out for the limiting cases of long and short nanocontacts. It is shown that the domain wall formed in a nanocontact causes considerable quantitative and qualitative changes in the dependence of the conductivity on the channel width.

On the Effect of Antiphase Domain Boundaries on ALCHEMI

The effect of antiphase domain boundaries (APB) on ALCHEMI (atomic location by channelling-enhanced microanalysis) is discussed in the context of a two-beam dynamical approach. Appropriate experimental conditions for ALCHEMI in TEM foils with APBs are suggested.

On the Effect of Antiphase Domain Boundaries on ALCHEMI

The effect of antiphase domain boundaries (APB) on ALCHEMI (atomic location by channelling-enhanced microanalysis) is discussed in the context of a two-beam dynamical approach. Appropriate experimental conditions for ALCHEMI in TEM foils with APBs are suggested.

A Monte–Carlo approach to domain boundary precipitation in binary alloys

A Monte–Carlo approach on the second phase precipitation in polycrystalline binary alloys is developed. The approach starts from the kinetic spin-exchange Ising model and the Q-state Potts model, and a coupling algorithm for simulation of both phase precipitation and domain growth is developed. The simulation on a simplified system with slow domain boundary migration reveals precipitation phenomena on the domain boundaries. The effect of domain boundaries on the morphology and kinetics of the second phase precipitates is investigated. It is shown that the scaling concept and the Lifshitz–Slyozov–Wagner law are broken in the present system.