Gao, HengjiaoXiong, YuqingZhang, KaifengWang, Wenxi...
8页查看更多>>摘要:The reaction process of deposition of Iridium coating on Mo (1 1 0) surface by atomic layer deposition (ALD) was studied theoretically by using the density functional theory and periodical slab model. The results indicated that the whole ALD reaction cycle of iridium deposition can be divided into two half-reaction processes, that the half reaction I was the reaction between iridium precursor (Ir(acac)(3)) and oxygen atom on Mo cluster, causing the chemical bond length of Ir-C to stretch and that of Mo-O to shorten, and forming a ring-like skeleton structure of transition state Mo-O-C-Ir, which was approximately a planar structure and presenting a fresh and active surface of (CH3)(2)*Ir-Mo-Ir(CH3)(2)*; In the half-reaction II, the oxygen atoms react with -(CH3)(2)* active group of (CH3)(2)*Ir-Mo-Ir(CH3)(2)* surface, causing the chemical bond length of Ir-C to stretch and that of O-O to shorten, forming a ring-like skeleton structure of transition state O-C-Ir-C, which was also approximately a planar structure and presenting a fresh and active O*-Ir-Mo-Ir-O* surface eventually. Furthermore, the by-products of every surface reaction were released in the form of CO2 and H2O. The experiment result shown that the surface of iridium coating deposited by ALD at 300 degrees C was flat and smooth, and the preferred growth crystal plane was (111). The theoretical conclusion was in good agreement with the experimental results.
原文链接:
NSTL
Elsevier
Yan, X. F.Tian, M. Y.Yan, J.Chen, Q....
5页查看更多>>摘要:The energy spectrum of bismuthene quantum dots in the presence of in-plane electric and exchange fields are investigated by the tight-binding method. In the case of an in-plane exchange field, bismuthine is a second-order topological insulator and supports corner states in triangular and hexagonal quantum dots with zigzag edges. The corner states in hexagonal bismuthene quantum dots are more stable than the corner states in triangular quantum dots. In hexagonal quantum dots, the corner states are degenerate at zero energy as the exchange field h > 0.18 eV. However, the degeneracy of corner states can be destroyed by the electrical fields, and the energy levels of corner states oscillate with respect to the electric field direction. In addition, the on-site disorders will not destroy the corner states but lead to the separation of these states around zero energy.
原文链接:
NSTL
Elsevier
Li, ZebinYang, MaoLi, LianbiTu, Zheyan...
8页查看更多>>摘要:Methylammonium iodo bismuthate (CH3NH3)3Bi2I9 (MBI) is a promising perovskite material to replace organic-inorganic hybrid lead-based perovskites because of its non-toxic and stable. In this paper, both the electronic structure and optical properties of hexagonal MBI was investigated by adopting the LDA-1/2 method and spinorbit coupling (SOC) effect was also taken into account. The calculated results showed that the [Bi2I9]3- anions in MBI forms a face-sharing bi-octahedral structure which form a three-dimensional constrained "quantum dot". The calculated band gap of MBI was 2.10 eV, which is in good agreement with the experimental value. The valence-band maximum (VBM) of MBI is mainly contributed by I-p electrons, while conduction-band minimum (CBM) is mainly contributed by Bi-p electrons. The thickness-dependent solar cell characteristic parameters including short circuit current (Jsc), open circuit voltage (Voc), fill factor (FF) and power conversion efficiency (PCE) of MBI were also calculated. This work predicted PCE of 11.50%, seven times higher than the current experimental value (1.64%), indicating potentials for engineering more efficient MBI-based solar cells.
原文链接:
NSTL
Elsevier
Risva, MariaSiafarika, PanagiotaKalampounias, Angelos G.
8页查看更多>>摘要:In this study, ultrasonic relaxation spectroscopy and molecular orbital calculations have been used to investigate the rotational-isomeric equilibria in isobutyl halide (CH3)(2)CH-CH2X (X = Cl, Br and I) liquids as a function of frequency and temperature under isobaric conditions. The sound absorption in the a/f(2) representation appeared to deviate from straight line with frequency in the MHz region revealing a single Debye-type relaxation process, which is attributed to thermal relaxation of a rotational isomeric equilibrium for all isobutyl halide systems. From the temperature dependence of the relaxation parameters, the associated thermodynamic parameters and the respective volume changes were estimated for each liquid and discussed in view of the outcome of density functional theory electronic structure calculations. The activation enthalpy was found to be strongly dependent on the ionic radius of the halide. Furthermore, the lower energy state of all isobutyl halide systems is two-fold degenerate. The experimental results indicate that a shear viscosity relaxation is questionable in the frequency region covered in this work. The observed-to-classical absorption ratio a/a(cl) and the volume-to-shear viscosity ratio n(V)/n(s) have been evaluated and used as a measure to monitor the strength of the intermolecular bonding. The values and the strong temperature dependence of these ratios are typical of a relaxation process associated to rotational isomers equilibrium. The results have been discussed in the context of inter- and intra-molecular interactions.
原文链接:
NSTL
Elsevier
Gharaibeh, MaenAl-Qawasmeh, AhmadObeidat, AbdallaAbedrabbo, Sufian...
12页查看更多>>摘要:This work implemented Monte Carlo (MC) simulation to study the phase diagrams and magnetic properties of a mixed spin (1-1/2-1) three-layer system with a cubic structure. The effect of the crystal field on the system compensation, critical temperatures, magnetic and thermodynamic properties of the system have been explored. The crystal field was found to have a profound impact on the system compensation and critical temperatures. Our results suggest that the presence of the crystal field will cause the compensation temperature to exist for a short range of negative crystal field values. Furthermore, the threshold values of the crystal field were found to determine the change in both the compensation and critical temperatures with the variation of the crystal field. Moreover, a first-order phase transition presents at the threshold values of D. Finally, the system reveals the presence of two-step hysteresis loops for some temperatures and crystal field values.
原文链接:
NSTL
Elsevier
Raj, S. SanthoshGhosh, NilotpalNavamathavan, R.
5页查看更多>>摘要:Study of normal-state behaviour of YbFe2As2 single crystals has been reported through transport, specific heat and magnetotransport measurements. The YbFe2As2 crystals have been synthesized by using melt growth aided method. It is found that Sommerfeld coefficient (gamma = 213.16 mJ mol(-1)K(-1)) is strongly enhanced suggesting existence of heavy quasiparticles. Analysis of resistivity data at low temperature yields Fermi-liquid co-efficient (A) value of 5.47 x 10(-5) Omega cm K-2. Evaluation of Kadowaki-Woods ratio (A/gamma(2) = 1.204 x 10(-5) mu Omega cm mole(2)mJ(-2)) indicates that the YbFe2As2 crystal is a strongly correlated metal. The scaling analysis of magnetoresistance (MR) has been carried out. We have observed from MR results that YbFe2As2 show quadratic behaviour on magnetic field up to 5 T and beyond that it shows linear nature. Additionally, the verification of Kohler's rule has been explored. The measurement of MR as a function of magnetic field (B) up to 8 T indicates that Kohler's rule is not satisfied in YbFe2As2. However, it is found that YbFe2As2 satisfies an unusual scaling relationship between applied magnetic field and temperature within limited temperature range, which was reported in other iron-based superconductors recently.
原文链接:
NSTL
Elsevier
Wang, LuoshuZhao, ChangjiangZhao, LeranFan, Xiaowei...
7页查看更多>>摘要:SiO2 thin film was deposited on quartz glass substrate with radio frequency (RF) magnetron sputtering. The effects of O2/Ar flow ratio and heat treatment on the O/Si molar ratio, surface morphology and optical properties of the film were investigated. SiO2 film was composed of amorphous nanoparticles. When the O2/Ar flow ratio increased from 30% to 60%, the film's O/Si ratio increased continuously from severe O-deficiency 1.68:1 to 1.93:1, close to the stoichiometric ratio 2:1. Meanwhile, the particles' average size decreased and became more uniform, and the surface roughness decreased with the O2/Ar flow ratio increase. And the film's refractive index and absorptivity decreased continuously, while the coated glass substrate's average transmittance (hereinafter referred to as the film's transmittance) within 300-1100 nm increased from 91.7% to 92.9% continuously. Heat treatment at 550 degrees C resulted in an obvious agglomeration of the nanoparticles, reduced the refractive index of the film and improved its transmittance.
原文链接:
NSTL
Elsevier
Borbon, SusanaLugo, ShadaiPineda, NayelyLopez, Israel...
7页查看更多>>摘要:ZnTiO3 monodispersed nanoparticles have been synthesized by sol-gel method in air atmosphere, room temperature and without templates. The material was characterized by X-ray diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), N2 physisorption analysis, and diffuse reflectance spectroscopy (DRS). Furthermore, the N719 dye loading capacity of ZnTiO3 was determined for the first time, yielding an adsorption comparable to traditional DSSC materials such as TiO2.
原文链接:
NSTL
Elsevier
Nagpal, D.Gajraj, VKumar, A.Gnanasekar, K., I...
10页查看更多>>摘要:Spinel-type novel compositions of mesoporous ternary metal oxides ZnFeNiO4 (ZFNO) and CoFeNiO4 (CFNO) microspheres were synthesized through a facile hydrothermal method with post calcination approach. X-ray powder diffraction and X-ray photoelectron spectroscopy studies reveal the phase pure spinel-type cubic crystal formation. Electron microscopic studies show the mesoporous microspheres were constructed by the porous nano-lamellae which are formed by the nanoparticles. Specific surface area of ZFNO and CFNO is found as 107 and 28 m(2) g(-1) with maximum pore diameter of 4 and 3 nm respectively. The optical Eg of ZFNO and CFNO is found to be 2.21 and 1.98 eV respectively. Impedance spectroscopy is used to study the electrical properties of the samples in the temperature range of 150-600 degrees C. The conductivity of CFNO is higher than that of ZFNO. The activation energy of conductivity is found to be 0.67 and 0.42 eV for ZFNO and CFNO respectively. Isothermal AC conductivity were analysed with Koops theory and Jonscher's power law. Frameworks of various theoretical models are considered in order to explain the frequency and temperature dependent conductivity. It is observed that the quantum mechanical tunnelling mechanism is consistent for conductivity's frequency exponent of ZFNO and only below 330 degrees C for CFNO.
原文链接:
NSTL
Elsevier
Aziz, AsimaAldaghfag, Shatha A.Zahid, MuhammadIqbal, Javed...
9页查看更多>>摘要:The full-potential linearized augmented plane wave (FP-LAPW) method was used to evaluate the structural, optical, electronic, and thermoelectric (TE) characteristics of X2NaIO6 (X = Pb, Sr) cubic double perovskite oxides. Pb2NaIO6 and Sr2NaIO6 revealed the semiconductor behavior with a direct band gap (E-g) of 3.75 eV and 5.48 eV, respectively. Furthermore, the optical parameters like absorption coefficient alpha(omega), reflectivity R(omega), optical conductivity sigma(omega), extinction coefficient k(omega), dielectric constants, and refractive index n(omega) are calculated. Electrical conductivity (sigma), figure of merit (ZT), Seebeck coefficient (S), thermal conductivity (k), and power factor (PF) are investigated for their thermoelectric (TE) features by using the Boltz-Trap package. Sr2NaIO6 attained the maximum value of ZT (0.7728) with PF of 206.3. Results of cubic X2NaIO6(X = Pb,Sr) double perovskite oxides revealed their potential application in TE and optoelectronic devices.
原文链接:
NSTL
Elsevier