Decrease In Lateral Size Research Articles

Graphitic-carbon nitride nanosheets as a new inorganic filler for improving energy storage density of PVDF-based dielectric composites

Graphitic-phase carbon nitride (g-C3N4) nanosheets with lateral size of 1000 nm, 500 nm, and 100 nm have been fabricated by a one-step thermal condensation method at different thermal treating temperatures and used as filler for poly(vinylidene fluoride) (PVDF)-based dielectric composites. The effects of its size and content on energy storage density of g-C3N4/PVDF composites are discussed. The experimental results show that the energy storage density of the composites containing 3 wt% g-C3N4 increases with the decrease of lateral size and could reach to 11.7 J cm−3 at 522 kV mm−1, much higher than pure PVDF of 5.8 J cm−3 at 386 kV mm−1. A finite element simulation is employed to describe electric field distribution within the composites and reveal further the role of g-C3N4 nanosheets on the energy storage behavior of the composites. This work provides a new inorganic filler for high energy storage density PVDF-based dielectric composites.

Ultrasmall and Monolayered Tungsten Dichalcogenide Quantum Dots with Giant Spin-Valley Coupling and Purple Luminescence.

Monolayered tungsten dichalcogenide quantum dots (WS2 QDs) have various potential applications due to their large spin–valley coupling and excellent photoluminescence (PL) properties. What is expected is that with the decrease in lateral size of QDs, the stronger quantum confinement effect will dramatically strengthen the spin–valley coupling and widen the band gap. However, ultrasmall monolayered WS2 QDs prepared by ion intercalation unavoidably undergo the problem of structural defects, which will create defect levels and significantly change their properties. In this study, we report that by annealing defective monolayered WS2 QDs in sulfur vapor, pristine monolayered WS2 QDs with an ultrasmall lateral size of ca. 1.8–3.8 nm can be obtained. The results show that the ultrasmall monolayered WS2 QDs exhibit a giant spin–valley coupling of ca. 821 meV. Moreover, the pristine ultrasmall monolayered WS2 QDs show purple PL centered at 416 nm, and the defect PL peaks in defective WS2 QDs can be effectively removed by annealing. All of these results afford the ultrasmall monolayered QDs various applications such as in optoelectronics, spintronics, valleytronics, and so on.

Formation mechanism of reverse kebab structure inside hollow nanotubes studied by molecular simulations

Formation of polymer crystals inside a hollow nanotube provides the potential for its interior functionalization. Based on dynamic Monte Carlo simulations, the formation mechanism of crystal lamellae with uniform orientation inside hollow nanotubes in polymer solutions was investigated. In nanotubes with lateral size smaller than the size of chain coils, inside segments prefer to orient along the long axis of the nanotubes, due to the confinement effect exerted by side surfaces. Thus, crystal lamellae with uniform orientation along the long axis of the nanotubes can be formed inside. Further investigations revealed that the formation of these reverse kebabs is codetermined by the degree of confinement and the strength of interfacial interaction. Both the increase of interfacial interaction and the decrease of lateral size can lead to the improvement of segmental orientation of inside segments, thus favoring the formation of the reverse kebabs.

Cathodic Corrosion at the Bismuth–Ionic Liquid Electrolyte Interface under Conditions for CO2 Reduction

Bismuth electrodes undergo distinctive electrochemically induced structural changes in nonaqueous imidazolium ([Im]+)-based ionic liquid solutions under cathodic polarization. In situ X-ray reflectivity (XR) studies have been undertaken to probe well-ordered Bi (001) films which originally contain a native Bi2O3 layer. This oxide layer gets reduced to Bi0 during the first cyclic voltammetry (CV) scan in acetonitrile solutions containing 1-butyl-3-methylimidazolium ([BMIM]+) electrolytes. Approximately 60% of the Bi (001) Bragg peak reflectivity is lost during a potential sweep between −1.5 and −1.9 V vs Ag/AgCl due to a ∼ 4–10% thinning and a ∼40% decrease in lateral size of Bi (001) domains, which are mostly reversed during the anodic scan. Repeated potential cycling enhances the thinning and roughening of the films, suggesting that partial dissolution of Bi ensues during negative polarization. The mechanism of this behavior is understood through molecular dynamics simulations using ReaxFF and density fu...

Controlling the distribution of oxygen functionalities on GO and utilization of PEDOT:PSS-GO composite as hole injection layer of a solution processed blue OLED

Graphene oxide (GO) was synthesis by Tour method. Particle size distribution effects of raw graphite on the resulting structural, morphological, optical and electrical properties of GO samples and their poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) composites are studied for the graphite particle distributions of <150, 45–75 and 25–45 μm. It is determined that particle size of raw graphite have an impact on oxidation degree, the chemical nature of oxygen functional groups on GO and it also affects the lateral size of obtained GO.PEDOT:PSS-GO composites are utilized as hole injection layer (HIL) in a solution process blue organic light emitting diode. Presence of GO caused negative differential resistance (NDR) and NDR intensity was decreased with the decrease in lateral size of GO, increase in the graphite particle size and carboxyl% of obtained GO. All PEDOT:PSS-GO composite based devices presented better performance than the bare PEDOT:PSS based reference device. The maximum luminous and external quantum efficiency values of the device that contain HIL of PEDOT:PSS-GO(150) were more than 40% and 50% higher than that of the reference, respectively. Two folds of increase in these performance values were able to be reached with the concentration optimization of GO/150 in PEDOT:PSS.

Calculation of van der Waals Interaction Energy in Free Liquid Films Accounting for Many-body Contributions

Abstract In our work, we have adopted a coupled fluctuating dipoles method based on a microscopic approach that accounts for many-body interactions to compute the van der Waals forces in free liquid films. We have analyzed the peculiarities of the surface forces in films with thicknesses of a few molecular diameters, where the macroscopic theory is not applicable. The problem addressed in our study is related to the influence of the nanobubble size on the energy of the liquid film formed when two nanobubbles approach each other. It is shown that the decrease in lateral size of the liquid film results in the diminution of the van der Waals specific attraction, a change in the contribution of many-body interactions to the total energy, and variation of the thickness dependence of the free excess energy of the liquid film.

Ferroelectricity in BaTiO3 nanoscopic structures

The ground-state polarization of BaTiO3 nanosized films and cells is studied using an atomic-level simulation approach based on a shell model with parameters obtained from first-principles calculations. We demonstrate that the critical thickness for ferroelectricity in a free-standing BaTiO3 stress-free film is 3.6 nm, and a decrease in lateral size to nanometric dimensions does not spoil the ferroelectric properties of the film. Nanocells with different lateral faces, BaO or TiO2 planes, present a different domain structure and polarization due to a strong surface effect.

Patterning and switching of nano-size ferroelectric memory cells

A “top-down” approach using e-beam lithography and a “bottom-up” one using self-assembly methods were used to fabricate ferroelelectric Pb(Zr,Ti)O3, SrBi2Ta2O9 and BaTiO3 nanostructures with lateral sizes in the range of 30 nm to 100 nm. Switching of single sub-100 nm cells was achieved and piezoelectric hysteresis loops were recorded using a scanning force microscope working in piezoresponse mode. The piezoelectricity and its hysteresis acquired for 100 nm PZT cells demonstrate that a further decrease in lateral size under 100 nm appears to be possible and that the size effects are not fundamentally limiting on increase density of non-volatile ferroelectric memories in the Gbit range.

100-nm lateral size ferroelectric memory cells fabricated by electron-beam direct writing

A fundamental limitation in the recent development of non-volatile ferroelectric memories of 64-Mbit to 4-Gbit densities was found to be the problem to scale ferroelectric capacitor cell sizes down below 1 μm2. In this paper we report on the preparation of ferroelectric memory cells with lateral sizes down to 100 nm using electron-beam direct writing. Switching of single 100-nm cells was achieved and piezoelectric hysteresis loops were recorded using a scanning force microscope working in piezoresponse mode. The piezoelectricity and its hysteresis acquired for 100-nm PZT cells demonstrate that a further decrease in lateral size under 100 nm appears to be possible and that the size effects do not fundamentally limit the increase of the density of non-volatile ferroelectric memories in the Gbit range.