Picometer Scale Research Articles

Atomic-Environment-Dependent Thickness of Ferroelastic Domain Walls

Domain walls are of increasing interest in ferroelectrics because of their unique properties and potential applications in future nanoelectronics. However, the thickness of ferroelastic domain walls remains elusive due to the challenges in experimental characterization. Here, we determine the atomic structure of ferroelastic domain walls and precisely measure the polarization and domain wall thickness at picometer scale using annular bright field imaging in an aberration-corrected scanning transmission electron microscope. We find that the domain wall thickness in PbZr0.2Ti0.8O3 and PbTiO3 thin films is typically about one-unit cell, across which the oxygen octahedron distortion behavior is in excellent agreement with first principles calculations. Remarkably, wider domain walls about two-unit cells in thickness are also observed for those domains walls are coupled with dislocations and underwent a compressive strain. These results suggest that the thickness of ferroelastic domain walls highly depends on their atomic environments. This study can help us to understand the past debatable experimental results and provide further insights into control of domain walls via strain engineering for their possible applications in nanoelectronics.

Tuning LaAlO3 lattice structure by growth rate at the picometer scale in LaAlO3/SrTiO3 heterostructures

Here, we report an abnormal lattice reconstruction of LaAlO3 in the LaAlO3/SrTiO3 two-dimensional electron liquid heterostructure using the layer-by-layer pulsed laser deposition. We found that the lattice structure change of the top LaAlO3 layer is at the picometer level and is mainly controlled by the oxygen vacancies with an abnormal dependence on the oxygen background pressure. The lattice of the LaAlO3 film expands with more oxygen vacancies grown with high oxygen pressure and collapses with less oxygen vacancies grown with low oxygen pressure. The in situ monitoring of reflective high energy electron diffraction shows the lattice change coincident to the layer-by-layer deposition period change, revealing a non-equilibrium correlation between the lattice and the deposition environment, instead of the commonly assumed equilibrium correlation.

Ligand-induced symmetry breaking, size and morphology in colloidal lead sulfide QDs: from classic to thiourea precursors

Colloidal lead chalcogenide quantum dots (CQDs) exhibit promising optoelectronic properties for applications in solar cell devices and as thermoelectrics. Herein, we report and discuss a ferroelectric structural distortion, at the picometer scale resolution, in PbS CQDs prepared using both classic and new synthetic pathways. The investigation was performed using synchrotron X-ray total scattering data and advanced methods of analysis that rely on a homo-core-shell model and evaluate the atomic arrangement, stoichiometry, size and morphology of nanocrystals. The CQDs show comparable size-dependent relative elongation, up to 0.7 % of one body diagonal of the cubic rock-salt structure, which corresponds to a rhombohedral lattice deformation. The findings suggest a joint role for the oleate ligands (which induce surface tensile strain) and the Pb(II) lone pair as the driving forces of the deformation. Pb displacements along the [111] direction, which provoke a ferrolectric distortion related to the lattice change, fall in the 0.0 – 0.1 Å. Overall, the findings suggest the local nature of the metal off-centering, leading to different average displacements which depend on the synthetic conditions.

An analytical model for the detection of levitated nanoparticles in optomechanics.

Interferometric position detection of levitated particles is crucial for the centre-of-mass (CM) motion cooling and manipulation of levitated particles. In combination with balanced detection and feedback cooling, this system has provided picometer scale position sensitivity, zeptonewton force detection, and sub-millikelvin CM temperatures. In this article, we develop an analytical model of this detection system and compare its performance with experimental results allowing us to explain the presence of spurious frequencies in the spectra.

Bending and breaking of stripes in a charge ordered manganite

In charge-ordered phases, broken translational symmetry emerges from couplings between charge, spin, lattice, or orbital degrees of freedom, giving rise to remarkable phenomena such as colossal magnetoresistance and metal–insulator transitions. The role of the lattice in charge-ordered states remains particularly enigmatic, soliciting characterization of the microscopic lattice behavior. Here we directly map picometer scale periodic lattice displacements at individual atomic columns in the room temperature charge-ordered manganite Bi0.35Sr0.18Ca0.47MnO3 using aberration-corrected scanning transmission electron microscopy. We measure transverse, displacive lattice modulations of the cations, distinct from existing manganite charge-order models. We reveal locally unidirectional striped domains as small as ~5 nm, despite apparent bidirectionality over larger length scales. Further, we observe a direct link between disorder in one lattice modulation, in the form of dislocations and shear deformations, and nascent order in the perpendicular modulation. By examining the defects and symmetries of periodic lattice displacements near the charge ordering phase transition, we directly visualize the local competition underpinning spatial heterogeneity in a complex oxide.

Mapping Picometer Scale Periodic Lattice Distortions with Aberration Corrected Scanning Transmission Electron Microscopy

Mapping Picometer Scale Periodic Lattice Distortions with Aberration Corrected Scanning Transmission Electron Microscopy

Multi-band optical bandpass filter with picometer bandwidth in visible spectrum formed by prism pair coupled planar optical waveguide.

An optical bandpass filter structure of multiple bands in the visible spectrum with bandwidths in picometer scale (full width at half maximum, FWHM) is theoretically analyzed. The filter is in a form of prism pair coupled planar optical waveguide. For each individual guided mode, multiple pass-bands are obtainable in violet, green, and red regions of the visible spectrum, respectively. High efficiencies and symmetric band shape with flat null sideband can be obtained with practical material dispersion and loss taken into account. The central wavelength of each band can also be angularly tuned within a certain range with little influence on the efficiency or bandwidth. This kind of ultra-narrow bandpass optical filter can be used in high resolution spectroscopies, laser technologies, optical communications, and optical sensing.

Measuring and imaging nanomechanical motion with laser light

We discuss several techniques based on laser-driven interferometers and cavities to measure nanomechanical motion. With increasing complexity, they achieve sensitivities reaching from thermal displacement amplitudes, typically at the picometer scale, all the way to the quantum regime, in which radiation pressure induces motion correlated with the quantum fluctuations of the probing light. We show that an imaging modality is readily provided by scanning laser interferometry, reaching a sensitivity on the order of 10, {mathrm {fm/Hz^{1/2}}}, and a transverse resolution down to 2,upmu {hbox {m}}. We compare this approach with a less versatile, but faster (single-shot) dark-field imaging technique.

Structure and ordering of oxygen on unreconstructed Ir(100)

The adsorption of oxygen on the unreconstructed Ir(100) surface is investigated by a combination of experimental and theoretical methods comprising low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and density-functional theory (DFT). Apart from the well-known $(2\ifmmode\times\else\texttimes\fi{}1)$-O phase, we find a new $(3\ifmmode\times\else\texttimes\fi{}1)$-O phase for temperatures below 180 K. Our DFT calculations predict these two phases to be the only fundamental ground states of the system in the coverage range up to 0.5 monolayers. An analysis of the phase transitions as a function of coverage reveals extended coexistence ranges between the clean surface and the $3\ifmmode\times\else\texttimes\fi{}1$ phase, or between the $3\ifmmode\times\else\texttimes\fi{}1$ and $2\ifmmode\times\else\texttimes\fi{}1$ phases, respectively. As a function of temperature, both phases undergo order-disorder transitions at about 650 K for the $2\ifmmode\times\else\texttimes\fi{}1$ phase and 180 K for the $3\ifmmode\times\else\texttimes\fi{}1$ phase, the latter being only partially reversible. The complete ordering behavior can be consistently explained by the energetics of model defect structures calculated by DFT. The crystallographic structure of the phases is determined by full-dynamical LEED intensity analyses, yielding excellent agreement between experimental and calculated data sets (Pendry $R$-factors: ${R}_{P}\ensuremath{\approx}0.1$). Oxygen was found to assume bridge sites always inducing significant relaxations within the substrate. The derived structural parameters coincide with the respective predictions from DFT on the picometer scale. It is also shown that remnants and precursor stages of the clean surface's reconstruction can only be detected through the application of real-space methods such as STM. The overarching objective of the present study is to demonstrate how precisely and accurately such an adsorption system can be investigated nowadays by using a concerted experimental and theoretical approach.

X-ray Observation of Novel Nucleation Factor in Protein Supersaturated Solution

Recently, Protein solution and the micro scale structure are receiving a lot of attention in diverse protein study. Protein crystal observation In particular, protein aggregation process is a typical micro scale phenomenon of protein solution. Moreover, it is a one of the unclear mechanism of protein characteristics.In this study, we approached to observe the time resolved micro scale dynamics of protein solution by Diffracted X-ray Tracking (DXT) as known as single molecule measurement method. This method is able to direct observation of local solution dynamics for Target solution by detecting angular rotational displacement of a coexisted and dispersed single gold nanocrystal (approximately 100 nm) with pico-meter scale positional accuracy and micro-second time resolution. For target sample, we choose a crystal precursor metastable state of lysozyme solution.From detailed DXT analysis, we observed as crystal precursor state solution of lysozyme are containing slow and fast dynamics and the fast diffusion corresponded relaxation process of metastable state of nano scale clusters which is a important factor of maintenance of metastable supersaturated condition, driving force of morphology determination of final product from crystallization and nucleation process from supersaturation. From this study, DXT measurement results and detailed analysis process for a protein solution such as crystal precursor metastable state of lysozyme solution are concerned that this technique is a powerful tool for observing nano-scale protein structures and its local dynamics in bulk solution. For next work, we will planning to tackle research in order to observe morphology control factor discovery inhibitation techniques of supersaturated condition, and approaching for elucidation of protein abnormal aggregation process.

On-chip read-out of picomechanical motion under ambient conditions.

Monitoring the nanomechanical movement of suspended cantilever structures has found use in applications ranging from biological/chemical sensing to atomic force microscopy. Interrogating these sensors relies on the ability to accurately determine the sub-nanometre movements of the cantilever. Here we investigate a technique based on the combination of integrated silicon photonics and microelectromechanical systems (MEMS) to create an optically resonant microcavity and demonstrate its use for monitoring of the position of cantilevers on the picometer scale under ambient conditions with dynamic range extending over several microns. The technique is interferometric, and we show it to be sufficiently sensitive to measure both the first and second modes of cantilever Brownian motion. We anticipate that application of this technique will provide a physically robust, picometer precision, integrated cantilever movement read-out technology which can take cantilever sensors from laboratory controlled environments into real world conditions, allowing everyday applications.

Nanostep height measurement via spatial mode projection

We demonstrate an optical scheme for measuring the thickness of thin nanolayers with the use of light beam's spatial modes. The novelty in our scheme is the projection of the beam reflected by the sample onto a properly tailored spatial mode. In the experiment described below, we are able to measure a step height smaller than 10 nm, i.e., one-eightieth (1/80) of the wavelength with a standard error in the picometer scale. Since our scheme enhances the signal-to-noise ratio, which effectively increases the sensitivity of detection, the extension of this technique to the detection of subnanometric layer thicknesses is feasible.

Structural Fluctuations and Aggregations of Tau Proteins from X-Ray Single Molecule Observations

Intrinsically disordered proteins have very important flexible structures. In order to analyze such proteins, we need new methodology for high-accuracy measurements of three- dimensional (3D) intra-molecular motions. The structure of tau proteins in solution resembles that of a random coil. But, tau proteins in Alzheimer paired helical filaments-like fibers have very little secondary structures. Here, we observed the 3D structural motions of tau proteins using Diffracted X-ray Tracking (DXT) as high-speed x-ray single molecule observations. In DXT, we observed Brownian motions of recombinant tau proteins and his-tagged tau proteins, which are adsorbed on the substrate's surface. These adsorbed tau proteins was reacted to many antibodies and was phosphorylated by several kinases. We succeeded in measuring three-dimensional (3D= 2 axes as polar coordinates) micro-second super-high accuracy (pico-meter scale) motion maps of individual single molecule observations at many conditions of the tau proteins. From dynamic DXT data, for example, the tau protein combined with the antibody was confirmed that structure fluctuation had become slightly large compared with that which is not combined. We discuss the aggregation process of tau protein from these dynamic intra-molecular data under many conditions.

Tracking 3D Picometer-Scale Motions of Single Nanoparticles with High-Energy Electron Probes

We observed the high-speed anisotropic motion of an individual gold nanoparticle in 3D at the picometer scale using a high-energy electron probe. Diffracted electron tracking (DET) using the electron back-scattered diffraction (EBSD) patterns of labeled nanoparticles under wet-SEM allowed us to super-accurately measure the time-resolved 3D motion of individual nanoparticles in aqueous conditions. The highly precise DET data corresponded to the 3D anisotropic log-normal Gaussian distributions over time at the millisecond scale.

The neutron and its role in cosmology and particle physics

Experiments with cold and ultracold neutrons have reached a level of precision such that problems far beyond the scale of the present standard model of particle physics become accessible to experimental investigation. Because of the close links between particle physics and cosmology, these studies also permit a deep look into the very first instances of our Universe. First addressed in this article, in both theory and experiment, is the problem of baryogenesis, the mechanism behind the evident dominance of matter over antimatter in the Universe. The question of how baryogenesis could have happened is open to experimental tests, and it turns out that this problem can be curbed by the very stringent limits on an electric dipole moment of the neutron, a quantity that also has deep implications for particle physics. Then the recent spectacular observation of neutron quantization in the Earth's gravitational field and of resonance transitions between such gravitational energy states is discussed. These measurements, together with new evaluations of neutron scattering data, set new constraints on deviations from Newton's gravitational law at the picometer scale. Such deviations are predicted in modern theories with extra dimensions that propose unification of the Planck scale with the scale of the standard model. These experiments start closing the remaining ``axion window'' on new spin-dependent forces in the submillimeter range. Another main topic is the weak-interaction parameters in various fields of physics and astrophysics that must all be derived from measured neutron-decay data. Up until now, about 10 different neutron-decay observables have been measured, much more than needed in the electroweak standard model. This allows various precise tests for new physics beyond the standard model, competing with or surpassing similar tests at high energy. The review ends with a discussion of neutron and nuclear data required in the synthesis of the elements during the ``first three minutes'' and later on in stellar nucleosynthesis.

Picoscale science and nanoscale engineering by electron microscopy

A future scanning/transmission electron microscope is proposed to be a comprehensive machine that is capable of providing picoseconds time-resolved information at sub-nanometer scale and even at picometer scale, spatial resolution. At the same time, physical and chemical properties can be measured in situ from a region as small as a few nanometers by introducing local electric, mechanical, thermal, magnetic and/or optical stimulations/excitations under vacuum or even in a quasi-ambient environment. It is anticipated that nanoscopy and picoscopy will be key tools for studying picoscale science and developing nanoscale technology related to materials science, biology, physics and chemistry.

Shedding Light on Axial Stress Effect on Resonance Frequencies of Nanocantilevers

The detection back-action phenomenon has received little attention in physical, chemical, and biological sensors based on nanomechanical systems. We show that this effect is very significant in ultrathin bimetallic cantilevers, in which the laser beam that probes the picometer scale vibration largely modifies the resonant frequencies of the system. The light back-action effect is nonlinear, and some resonant frequencies can even be reduced to a half with laser power intensities of 2 mW. We demonstrate that this effect arises from the stress and strain generated by the laser heating. The experiments are explained by two-dimensional nonlinear elasticity theory and supported by finite element simulations. The found phenomenology is intimately connected to the old unsolved problem about the effect of surface stress on the resonance frequency of singly clamped beams. The results indicate that to achieve the ultimate detection limits with nanomechanical resonators one must consider the uncertainty due to the detection back-action.

Probing the Out-of-Plane Distortion of Single Point Defects in Atomically Thin Hexagonal Boron Nitride at the Picometer Scale

Crystalline systems often lower their energy by atom displacements from regular high-symmetry lattice sites. We demonstrate that such symmetry lowering distortions can be visualized by ultrahigh resolution transmission electron microscopy even at single point defects. Experimental investigation of structural distortions at the monovacancy defects in suspended bilayers of hexagonal boron nitride (h-BN) accompanied by first-principles calculations reveals a characteristic charge-induced pm symmetry configuration of boron vacancies. This symmetry breaking is caused by interlayer bond reconstruction across the bilayer h-BN at the negatively charged boron vacancy defects and results in local membrane bending at the defect site. This study confirms that boron vacancies are dominantly present in the h-BN membrane.

Controlling the interparticle distance in a 2D molecule–nanoparticle network

Mechanically controllable break junctions allow for an impressive level of control over thedistance between two electrodes, but lack stability at room temperature. On the otherhand, two-dimensional (2D) networks of nanoparticles bridged by molecules form a stabledevice structure for investigating molecular conductance properties. Here, we combine bothtechniques to create a robust platform for molecular charge transport with control over theinter-electrode distance on the picometer scale. The resistance change due to bending ofour structures is dependent on the molecular species present between the nanoparticles.

Strong coupling between on chip notched ring resonator and nanoparticle

We have demonstrated a new photonic structure to achieve strong optical coupling between nanoparticle and photonic molecule by utilizing a notched microring resonators. By creating a notch in the ring resonator and putting a nanoparticle inside the notch, large spectral shifts and splittings at nanometer scale can be achieved, compared to only picometer scale observed by fiber tip evanescently coupled to the surface of microsphere, thereby significantly lowered the quality factor requirement for single nanoparticle detection. The ability for sorting the type of nanoparticles due to very different mode shift and splitting behavior of dielectric and metallic nanoparticles is also emphasized.