Meyer–Neldel DC conduction in chalcogenide glasses

Meyer–Neldel (MN) formula for DC conductivity (σ _DC) of chalcogenide glasses is obtained using extended pair model and random free energy barriers. The integral equations for DC hopping conductivity and external conductance are solved by iterative procedure. It is found that MN energy (ΔE _MN) originates from temperature-induced configurational and electronic disorders. Single polaron-correlated barrier hopping model is used to calculate σ _DC and the experimental data of Se, As₂S₃, As₂Se₃ and As₂Te₃ are explained. The variation of attempt frequency ν ₀ and ΔE _MN with parameter (r/a), where r is the intersite separation and a is the radius of localized states, is also studied. It is found that ν ₀ and ΔE _MN decrease with increase of (r/a), and ΔE _MN may not be present for low density of defects.     

Pre-exponential factor for the crystallization of glassy Se80Te20 and Se75Te20M5 alloys: applicability of Meyer–Neldel rule

The Meyer–Neldel rule or MN rule (also known as compensation effect) is an empirical law known since 1937. This rule is observed in wide range of phenomena in physics, chemistry, biology and electronics. Many activated phenomena, including solid state diffusion in crystals and polymers, dielectric relaxation, conduction and thermally stimulated processes in polymers, and electronic conduction in amorphous semiconductors obey the MN rule. In the present article, we report the MN rule in the non-isothermal crystallization in glassy Se₈₀Te₂₀ and Se₇₅Te₂₀M₅ (M = Ag, Cd, In, Sb) alloys. We have observed MN rule between pre-exponential factor K _o and activation energy of crystallization E _c in the present case for thermally activated non-isothermal crystallization.     

Meyer–Neldel energy in Se-based binary and ternary chalcogenide glasses

This paper investigates the cluster-modified function projective synchronisation (CMFPS) of a generalised linearly coupled network with asymmetric coupling and nonidentical dynamical nodes. A novel synchronisation scheme is proposed to achieve CMFPS in community networks. We use adaptive control method to derive CMFPS criteria based on Lyapunov stability theory. Each cluster of networks is synchronised with target system by state transformation with scaling function matrix. Numerical simulation results are presented finally to illustrate the effectiveness of this method.     

Correlation between Meyer–Neldel rule and phase separation in Se98−xZn2Inx chalcogenide glasses

The present work reports the observation of Meyer–Neldel rule for the thermally activated crystallization of glassy Se_98−xZn₂In_x (0 ⩽ x ⩽ 10) alloys. We have observed a strong co-relation between the pre-exponential factor K₀ of rate constant K(T) of crystallization and activation energy of crystallization E_c in the present case. This indicates the presence of compensation effect for the non-isothermal crystallization process in the present glassy system, which is explained in terms of phase separation of the present alloys due to flaw bonds of these amorphous solids.     

Spectroscopy of thermally excited acoustic modes using three-mode opto-acoustic interactions in a thermally tuned Fabry–Pérot cavity

Three-mode opto-acoustic interactions can excite acoustic modes of the mirrors of an optical cavity. This was achieved when the frequency difference between the fundamental and higher order optical mode matches the frequency of appropriate acoustic mode of the mirror. The excitation also critically depends on the spatial overlap between acoustic and optical modes. In this Letter, we use a controlled CO₂ laser to thermally change the radius of curvature of one mirror of an 80 m Fabry–Pérot cavity for three-mode interaction. Several acoustic modes of the cavity end mirror were observed with quality factors of ∼10⁵–10⁶$\sim {10}^5\text{–}{10}^6$ at the thermal noise level.     

Room temperature synthesis of an optically and thermally responsive hybrid PNIPAM–gold nanoparticle

Composites of metal nanoparticles and environmentally sensitive polymers are useful as nanoactuators that can be triggered externally using light of a particular wavelength. We demonstrate a synthesis route that is easier than grafting techniques and allows for the in situ formation of individual gold nanoparticles encapsulated by an environmentally sensitive polymer, while also providing a strong interaction between the polymer and the metal particle. We present a one-pot, room-temperature synthesis route for gold metal nanoparticles that uses poly-N-isopropyl acrylamide as the capping and stabilizing agent and ascorbic acid as the reducing agent and achieves size control similar to the most common citric acid synthesis. We show that the composite can be precipitated reversibly by temperature or light using the non-radiative decay and conversion to heat of the surface plasmon resonance of the metal nanoparticle. The precipitation is induced by the collapse of the polymer cocoon surrounding each gold nanoparticle, as can be seen by surface plasmon spectroscopy. The experiments agree with theoretical models for the heat generation in a colloidal suspension that support fast switching with low laser power densities. The synthesized composite is a simple nanosized opto-thermal switch.     

Emitting layer analysis of blue thermally activated delayed fluorescence devices using capacitance–voltage method

In this paper, blue thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs) have been elucidated, with a focus on the degradation characteristics of the emission layer (EML). The operational stability against electrical stress was investigated for two host materials and four doping concentrations, which were used as the EML. The operating stability of the devices was confirmed by comparing the peak capacitance before and after degradation. Devices using bis [2-(diphenyl-phosphino) phenyl] ether oxide (DPEPO) as a host exhibited poor degradation characteristics. However, high stability was confirmed when 3,3-di (9H-carba-zol-9-yl)-biphenyl (mCBP) was used. DPEPO host devices are most resistant against performance degradation when they are doped with 10 wt% 10,10'-(4,4′-sulfonylbis(4,1-phenylene))bis(9,9-dimethyl-9,10-dihydroacridine (DMAC-DPS). We successfully determined the electroluminescence characteristics of the device depending on the host material, as well as the doping concentration, using the capacitance–voltage method.     

Interface resistance dependence of spin transport in a ferromagnet–semiconductor hybrid structure

The spin transport signals from NiFe and Co into two-dimensional electron gas layers are measured for various thicknesses of transmission barriers. A stable and reproducible electrical detection of spin transport was obtained only when the barrier thickness is less than 10 nm. The typical interface resistance to observe spin signals in this experiment is about 0.5–250 Ω, which is a neither transparent nor a severe tunneling limit. The optimal interface resistance depends on the ferromagnetic materials, but severe tunneling barrier is not proper for fully electrical spin transport. Device size is also a critical factor to decide the proper range of interface resistance.     

Reaction-diffusion-induced explosive crystallization in a metal–selenium nanometer film structure

Experimental data for reaction-diffusion-induced explosive crystallization in a nanodimensional metal (Cu, Ag)/selenium structure are presented. It is found that after the metal layer has completely diffused into the amorphous Se film, the electrical potential rises from 0.14 to 1.21 V in the Cu(30 nm)/Se(140 nm) heterolayer and from 0.01 to 1.17 V in the Ag(30 nm)/Se(140 nm) heterolayer. The metals diffusing into the amorphous Se layer interact with Se, forming nuclei of a new phase (CuSe or Ag₂Se). The intense growth of the CuSe and Ag₂Se crystallization centers results in a considerable liberation of latent energy in the form of phase transformation heat and in explosive growth of CuSe and Ag₂Se nanocrystalline particles. The mean size of CuSe and Ag₂Se crystallites equals 25 and 50 nm, respectively.     

Enhancing coupling coefficient in a hybrid nanotoroid–nanowire system

Enhancing light–matter interaction in cavity quantum electrodynamics has aroused widespread interests in on-chip quantum information processing. Here, we propose a hybrid nanotoroid–nanowire system to enhance photon–exciton interaction. A nanoscale gap is formed by placing a dielectric nanowire close to a dielectric nanotoroid, where the coupling coefficient between photon and emitter can achieve 5.55 times of that without nanogap. Meanwhile, the cavity loss and spontaneous emission of the emitter will remain at a small value to guarantee the realization of strong coupling. The method might hold promise for the research of nanophotonics,quantum optics, and novel optical devices.     

Experimental Observation of Kink in a Perfect Bidimensional Granular System

The kink formation in a vertical vibrated granular layer has been widely studied in three-dimensional systems, but there are few if any experimental reports on bidimensional granular layers. We report the kink formation newly found in a perfect bidimensional granular system. We measure the range of the driving frequencies and dimensionless accelerations for kinks. Furthermore, we observe a heaping process, which is caused by co-operative action of the kink-associated convection and the sidewall=associated convection.     

Study of inverse a.c. Josephson effect in Y–Ba–Cu–O and Y–8a–Sr–Cu–O

Microwave induced d.c. voltage due to inverse a.c. Josephson effect has been observed across bulk samples of Y-Ba-Cu-O and Y-Ba-Sr-Cu-O. The d.c. voltage is found to vary with microwave power, frequency and also with small external magnetic fields. Although the resistivity curve of Y-Ba-Cu-O does not show any appreciable resistance drop around 230 K, the microwave induced d.c. voltage due to the inverse a.c. Josephson effect has been found to exist upto 230 K. The resistivity behaviour of Y-Ba-Sr-Cu-O shows a sharp resistivity drop above 230 K. In this sample the inverse Josephson effect is found to exist upto +26 °C, indicating the presence of a phase having a superconducting onset around this temperature.     

Dynamics of a new composite four–Scroll chaotic system

A new three-dimensional autonomous chaotic system is proposed. This new system can generate single-scroll, double-scroll, three-scroll and four-scroll attractors under different system parameters. Particularly, it can generate a four-scroll chaotic attractor composed of a large Chua-like attractor and a small Lorenz-like attractor. And the system can also generate a nested three-scroll attractor and the multi-double-scroll chaotic attractor. In addition, the system possesses the chaotic state transition, and the number of scrolls will change in the state transition process. The formation mechanism of the composite four-scroll chaotic attractor is analyzed in detail. The dynamic analysis methods include time series, 0–1 test chart, phase diagram, bifurcation diagram and Lyapunov exponents are used to describe some basic dynamics behaviors of the proposed system.     

Sol–gel nonhydrolytic synthesis of a hybrid organic–inorganic electrolyte for application in lithium-ion devices

A new inorganic–organic hybrid electrolyte was synthesized by a nonhydrolytic sol–gel simple route without specific treatment of the reagents. The hybrid ion conductor is prepared with citric acid (CA), tetraethyl-orthosilicate (TEOS) and ethylene glycol (EG), forming polyester chains. The time-consuming drying step, required in most of the chemical syntheses, is not necessary for the preparation of the present hybrid electrolyte, pertaining to the polyelectrolyte class because only Li⁺ is mobile in the polymeric chain. The effect of the concentration of Li is investigated in terms of the Li-ionic conductivity. The new hybrid conductor is shown to be fully amorphous at room temperature with the vitreous transition temperature around 228 K (−45 °C). The material is solid, transparent and displays an ionic conductivity above 10⁻⁵ (Ω cm)⁻¹, besides presenting a great reproducibility of all these characteristics.     

Observation of Diffusion Process of a Water Droplet Immersed in Protein Solution in Microgravity

Pure liquid-liquid diffusion driven by concentration gradients is hard to study in a normal gravity environment since convection and sedimentation also contribute to the mass transfer process. We employ a Math Zehnder interferometer to monitor the mass transfer process of a water droplet in EAFP protein solution under micro- gravity condition provided by the Satellite Shi Jian No 8, A series of the evolution charts of mass distribution during the diffusion process of the liquid droplet are presented and the relevant diffusion coefficient is determined.     

Observation of polarized atoms of rubidium isotopes in experiments on optical orientation in a He–Rb mixture under conditions of a pulsed gas discharge

We are the first to have observed magnetic resonance signals from atoms of ⁸⁵Rb and ⁸⁷Rb isotopes when using the indirect optical orientation in conditions of helium–rubidium gas discharge plasma. An anomalously small ratio of magnetic resonance signals from isotopes of rubidium and metastable helium upon optical orientation of ⁴Не atoms has been detected. The experimental results have been considered theoretically, and an explanation of the observed anomaly in the signals is presented.Z     

Investigation of hydrogen storage in MWCNT–TiO2 composite

The hydrogen storage capacity of MWCNT–TiO₂ composite has been evaluated in the present work. The composite has been prepared by means of ultrasonication followed by drop casting on substrates. Morphology, structural and functional group studies of the prepared samples are carried out by transmission electron microscopy (TEM), scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. Then, the samples are hydrogenated in the hydrogenation chamber as a function of time. Hydrogen storage capacity of the composite sample is found to be 0.9 wt% at 100 °C. Hydrogen uptake of the composite is accounted for the spillover mechanism in CNTs–metal oxide composite. Desorption temperature range, activation energy of desorption, binding energy of hydrogen are determined from thermogravimetric (TG) analysis.     

Enhancement of Frster energy transfer from thermally activated delayed fluorophores layer to ultrathin phosphor layer for high color stability in non-doped hybrid white organic light-emitting devices

Fluorescence/phosphorescence hybrid white organic light-emitting devices(WOLEDs) based on double emitting layers(EMLs) with high color stability are fabricated.The simplified EMLs consist of a non-doped blue thermally activated delayed fluorescence(TADF) layer using 9,9-dimethyl-9,10-dihydroacridine-diphenylsulfone(DMAC-DPS) and an ultrathin non-doped yellow phosphorescence layer employing bis[2-(4-tertbutylphenyl)benzothiazolato-N,C2']iridium(acetylacetonate)((tbt)_2Ir(acac)).Two kinds of materials of 4,7-diphenyl-1,10-phenanthroline(Bphen) and 1,3,5-tris(2-Nphenylbenzimidazolyl) benzene(TPBi) are selected as the electron transporting layer(ETL),and the thickness of yellow EML is adjusted to optimize device performance.The device based on a 0.3-nm-thick yellow EML and Bphen exhibits high color stability with a slight Commission International de l'Eclairage(CIE) coordinates variation of(0.017,0.009) at a luminance ranging from 52 cd/m~2 to 6998 cd/m~2.The TPBi-based device yields a high efficiency with a maximum external quantum efficiency(EQE),current efficiency,and power efficiency of 10%,21.1 cd/A,and 21.3 lm/W,respectively.The ultrathin yellow EML suppresses hole trapping and short-radius Dexter energy transfer,so that Forster energy transfer(FRET)from DMAC-DPS to(tbt)_2Ir(acac) is dominant,which is beneficial to keep the color stable.The employment of TPBi with higher triplet excited state effectively alleviates the triplet exciton quenching by ETL to improve device efficiency.