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Dear authors, Thank you very much for your contribution to Chinese Physics B. Your paper has been published in Chinese Physics B, 2014, Vol.23, No.2. Attached is the PDF offprint of your published article, which will be convenient and helpful for your communication with peers and coworkers. Readers can download your published article through our website http://www.iop.org/cpb or http://cpb.iphy.ac.cn What follows is a list of related articles published recently in Chinese Physics B.

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Chin. Phys. B Vol. 23, No. 2 (2014) 027305

A strategy of enhancing the photoactivity of TiO2 containing nonmetal and transition metal dopants⇤ Li Wei(李 伟), Wei Shi-Hao(韦世豪), and Duan Xiang-Mei(段香梅)† Faculty of Science, Ningbo University, Ningbo 315211, China (Received 23 July 2013; revised manuscript received 11 September 2013; published online 20 December 2013)

An effective structural codoping approach is proposed to modify the photoelectrochemical (PEC) properties of anatase TiO2 by being doped with nonmetal (N or/and C) and transition metal (Re) elements. The electronic structures and formation energies of different doped systems are investigated using spin-polarized density functional theory. We find that (C, Re) doped TiO2 , with a low formation energy and a large binding energy, reduces the band gap to a large extent, thus it could contribute to the significant enhancement of the photocatalytic activity in the visible-light region. It should be pointed out that, to be successful, the proper proportion of the dopants C and Re should be controlled, so that reasonable PEC properties can be achieved.

Keywords: codoping, photoactivity, density functional theory, formation energy PACS: 73.50.Pz, 61.72.Bb, 71.20.Nr, 84.60.–h

DOI: 10.1088/1674-1056/23/2/027305

1. Introduction TiO2 has become one of the most promising photocatalysts for photoelectrochemical (PEC) water splitting due to its high chemical stability and strong catalytic activity. However, its large band gap of 3.2 eV has hindered its usage as an ideal photoelectrode, because it absorbs only the ultraviolet portion of light, which amounts to ⇠ 4% of solar energy. [1] To reduce the band gap and thus improve its efficiency under visible light, many efforts have been made by using various dopants. [1–6] Ever since Asahi et al. [7] discovered that TiO2 x Nx films and powders exhibited better optical absorption and photocatalytic activity than pure titania under visible light, nonmetal doping, especially N and C, of TiO2 has been investigated widely as a promising photocatalyst. [8–13] It has been demonstrated that the photocatalytic efficiency of non-metal mono-doping TiO2 decreases because strongly isolated empty states in the band gap may trap the photo-excited electron–hole pairs and reduce photo-generated current. [14] On the other hand, transition metal doping can promote photocatalytic efficiency [15,17–20] as well. Choi et al. [15] reported that doping with transition metals, including Re, in TiO2 significantly increases the photo-reactivity for both oxidation and reduction. Actually, the transition metal-doped TiO2 is impeded by the presence of carrier recombination centers and the formation of strongly localized states in the band gap, which is detrimental to carrier mobility. [16] To improve the photocatalytic efficiency of TiO2 , the challenge is to place its band edges at proper positions, thus shifting its absorption edge toward the visible light region. [21–26] Recently, using first-principles calculations, Gai et al. [6] have investigated the photocatalytic activity in compensated donor-acceptor, (Mo + ⇤ Project

C), codoping TiO2 and found enhanced visible-light photocatalytic efficiency. According to the extensive density functional theory (DFT) band structure calculations, Yin et al. [5] predicted that (Ta, N) and (Nb, N) pairs are the optimal codoping combinations in the high-concentration regime, and (Mo, 2N) and (W, 2N) complexes are good candidates in the lowconcentration regime for engineering TiO2 . To the best of our knowledge, there is no theoretical study regarding the comparison of the photocatalytic activity between the nonmental N (or/and C) and Re codoped TiO2 . In the present work, we investigate structural and optical properties of various codoped TiO2 by N (or/and C) and Re using spin-polarized DFT. We find that codoping results in a more effective band gap narrowing than monodoping, especially (C, Re), (CN, Re), and (3N, Re)-Re codopings obviously reduce the band gap further than other doped cases. Combining their formation and binding energies, we predict that (C, Re) may play an important role in developing the efficient photocatalysts.

2. Computational details All of the spin-polarized DFT calculations were performed by the PWSCF code based on the plane-wave method. [27] Exchange–correlation effect is treated in the generalized gradient approximation (GGA), and the interaction between the valence electrons and the ionic core is described by the Perdew–Burke–Ernzerhof gradient-corrected functional and ultrasoft pseudopotentials. The k space integration was done with the Monkhorst–Pack grid with 2 ⇥ 2 ⇥ 2 k-points for geometry optimization and 4 ⇥ 4 ⇥ 4 k-points for

supported by the National Natural Science Foundation of China (Grant No. 11074135). author. E-mail: [email protected] © 2014 Chinese Physical Society and IOP Publishing Ltd † Corresponding

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http://iopscience.iop.org/cpb   http://cpb.iphy.ac.cn

Chin. Phys. B Vol. 23, No. 2 (2014) 027305 electronic property calculations in the Brillouin zone of the supercell, and the wave functions are expanded with kinetic energy cutoff of 30 Rydberg. [28–31] The optimized lattice pa˚ and rameters for pure anatase were found to be a = 3.798 A ˚ c = 9.511 A, which are consistent with other experimental and theoretical results, [32,33] indicating that our method is reasonable. The supercell consists of 48 atoms with 2 ⇥ 2 ⇥ 1 repetition of the unit bulk anatase primitive cell. For monodoping, we consider that the N or C atom substitutes for O atoms and the Re atom substitutes for Ti atoms. For codoping, acceptor and donor codoped TiO2 is modeled by taking into account the different possibilities. The most stable geometries are double checked with the larger 3 ⇥ 3 ⇥ 1 supercell with 108 atoms. To see whether the defect pairs can form, we calculate the binding energy of defect pairs in the host lattice. The binding energy Eb of the dopants, such as NO and ReTi , is defined as Eb = E(pure) + E(N, Re)

E(NO )

E(ReTi ),

 ni µi +q(Ev +EF +DV ),

3.1. Structural properties The optimized local structures of (C, Re) (CN, Re), and (3N, Re) codoped in TiO2 are shown in Fig. 1. Due to the difference in atomic radius between the dopants and host atoms, it can be seen that dopants induce local lattice distortion in their neighbourhood, otherwise the host lattice remains almost unchanged. The change of the C–Re or N–Re bond length is calculated to be around 1%, corresponding to a small contraction relative to O–Ti distance, and the distance between O and Re along the c axis is extended by ⇠ 2%.

(1)

where E(pure) is the total energy of the pure TiO2 , and E(N, Re), E(NO ), and E(ReTi ) are the total energies for supercells containing defects (N, Re), NO , and ReTi , respectively. A negative value of Eb corresponds to a metastable or a stable bound dopant pair when both are present in the system. Extension of Eq. (1) to charged states is straightforward. The formation energies of substitutional dopant defects are defined by Ef = E(defect, q) E(pure)

3. Results and discussion

(2)

i

where E(defect, q) is the total energy of the system containing the impurity, E(pure) is the total energy of the pure host supercell, ni and µi are the number and chemical potential of the atoms added to (positive ni ), or taken from (negative ni ), the bulk reference supercell in order to create the defect. EF is the Fermi level, with respect to the valence band maximum (VBM), Ev is the bulk VBM, and DV is a correction term, which can be obtained by aligning the reference potential in the defect supercell to that in the bulk. [34] The atom chemical potential, µi , depends on the experimental condition under which the material is grown. For a Ti-rich condition, µTi = ETi (bulk), and for an oxygen-rich condition, µO = 1/2E(O2 ), where ETi (bulk) and E(O2 ) are the total energy of a Ti atom in bulk Ti and the energy of an oxygen molecule, respectively. The chemical potential for oxygen (titanium) under Ti-rich (O-rich) conditions can be determined from the assumption of thermal equilibrium: µTi + 2µO = µTiO2 , where µTiO2 is the chemical potential of TiO2 , the total energy of a bulk TiO2 stoichiometric unit. The chemical potentials of µN , µC , and µRe are determined by µN = µTiN µTi , µC = µTiC µTi , and µRe = µReO3 3µO , respectively.

Ti

O

C

N

Re

Fig. 1. (color online) Optimized geometries of (C, Re), (CN, Re), and (3N, Re) doped in TiO2 .

The calculated binding energies of considered defect pairs are shown in Table 1. Negative values of Eb indicate that the defect pairs are preferable with respect to the isolated impurities in the host. For the codoped systems, the (C, Re) and (N, Re) complexes each have a tendency to attract an N atom on the nearest-neighbour O sites, forming (CN, Re) and (2N, Re) combinations. The formation of the (3N, Re) complex is also stable. Table 1. Binding energies, Eb , (in eV) for codoped TiO2 . Eb

(N, Re) –2.20

(2N, Re) –4.63

(3N, Re) –6.59

(C, Re) –3.51

(CN, Re) —5.78

The formation energy describes the relative difficulty for different ions to be incorporated into the host lattice and is a widely accepted gauge of energetic stability. In Fig. 2 we present the calculated formation energies for the considered defects, each as a function of the Fermi level, EF , under O-rich (a) and Ti-rich (b) conditions. Under oxygen-rich conditions, Re donor has a low formation energy and thus contributes to the n-type conductivity. Note that, in reality, CO , NO , (2N, Re), (CN, Re), and (3N, Re) codoped TiO2 could be incorporated under a Ti-rich condition, where (N, Re), (2N, Re), and (C, Re) codoping have lower formation energies than the (CN, Re) and (3N, Re) codoping. For (CN, Re) and (3N, Re) codoping, it is clearly a high formation energy indicating that the concentration of such a structure under thermal equilibrium will be low. It is possible that these structures may form under nonequilibrium growth conditions.

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Chin. Phys. B Vol. 23, No. 2 (2014) 027305 3.2. Electronic and optical properties 4 Formation energy/eV

(a)

The calculated band gap of pure anatase TiO2 is 2.10 eV, which is consistent with other theoretical results, but underestimates the experimental value of 3.2 eV due to well-known limitations in density functional theory. In this study, we focus on the change of the band gap upon doping, and the generalized gradient approximation method is expected to largely cancel the band gap error between different systems. Recent theoretical work of nonmetal codoping with transition metals has shown that standard density functional theory methods can deal fully with these doped systems. [5,26] As shown in Fig. 3(a), the valence band maximum (VBM) of pure TiO2 is dominated by O-2p states while the conduction band minimum (CBM) consists mainly of Ti-3d states. The substitutional NO introduces acceptor states, contributed by N-2p orbital, above the valence band maximum [see Fig. 3(b)]. The empty N2p states may act as traps for excited electrons, which could promote an electron–hole recombination rate. For the carbon mono-doped case, CO , the 2p states of carbon are localized in the band gap without changing the valence band maximum relative to the undoped case, while its conduction band minimum shifts down [Fig. 3(c)]. The electron in the valence band can be excited into gap states and then subsequently to the conduction band by visible-light absorption. For the Re-doped TiO2 as shown in Fig. 3(d), the donor states below the conduction band minimum lead to the down shift of the conduction band minimum.

ReTi

2 CO

(C, Re)

0

(N, Re) NO

-2 (CN, Re)

Re) (2N,

-4

(3N, Re) -6

2 1 Fermi energy/eV

0

3

6 NO

Formation energy/eV

4

(3N, Re)

2 (CN, Re) 0

e) (2N, R

e) (C, R

-2

CO

Re) (N,

-4 ReTi

-6 -8

0

(b)

2 1 Fermi energy/eV

3

Fig. 2. (color online) Formation energies each as a function of the Fermi level for defects and complexes in TiO2 for O-rich conditions (a) and for Ti-rich conditions (b). The zero of the Fermi level is at the top of the valence band maximum. Kinks in the curves indicate transitions between different charge states.

O2p

2

(a)

0

0 Partial density of states/arb. units

(e)

O2p

2

Ti3d

-2

N2p

2

-2

Ti3d

2

N2p

(b)

0 Re5d

-2

0

C2p

(g)

N2p

2

-2 2

(f)

0

(c)

Re5d

-2

0

(h)

C2p

2 0

-2 Re5d

2

(d)

Re5d

-2 2

0

N2p

(i)

C2p

0

-2

Re5d

-2 -4

-2

0 2 Energy/eV

4

-6

-4

-2 0 Energy/eV

2

4

Fig. 3. (color online) Partial densities of states for (a) pure anatase; (b)–(d): monodoping NO , CO , and ReTi , respectively, (e)–(i): (N, Re), (2N, Re), (3N, Re), (C, Re), (CN, Re)-codoped cases. In all cases, the vertical dashed line indicates the VBM of pure TiO2 .

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Chin. Phys. B Vol. 23, No. 2 (2014) 027305

I(w) = 21/2 w[e12 (w) + ie22 (w)]1/4

21/2 we1 (w)1/2 .

(3)

The optical coefficients for (C, Re), (CN, Re), and (3N, Re)codoped TiO2 are compared with that of bulk TiO2 as shown in Fig. 4. An electron is taken away from the system to ensure that the system is neutral, and to enable the calculating of the optical absorption spectrum of (C, Re) doping. Obviously, these codopings would lead to much better absorption edges under sunlight. As is well-known, PEC water splitting for hydrogen production using TiO2 must simultaneously meet three requirements: it must be stable, efficient and energy favorable. [6,25] By comparison, the (C, Re)-codoped anatase TiO2 has the potential to fit these requirements. Therefore this

type of codoped TiO2 is expected to significantly improve the PEC water-splitting efficiency. 8 Optical absorption

Considering that the defect states of C and N are mainly located at the edge of the valence band, and the Re-5d states only contribute to the lowering of the CBM, it is expected that their codoping would enhance the mixing of N (or C)2p and O-2p states in the valence band. We find that for the (N, Re)-doped case, the empty minority band of nitrogen vanishes completely from the gap [see Fig. 3(e)]. A small shift of the VBM (relative to the vertical dashed line) (0.18 eV) indicates that (N, Re) doping contributes less to the improvement of photocatalytic efficiency. For the (2N, Re)-doped case [see Fig. 3(f)], similarly, no impurity state exists within the band gap, and the VBM moves further towards a higher energy compared with that of (N, Re) combination. Doping N further to form complex (3N, Re), the non-equivalent N atoms induce VBM to significantly shift up (0.74 eV) as shown in Fig. 3(g). For (C, Re)- and (CN, Re)-doped systems, the VBM increases greatly. There are strongly mixed characteristics from the dopants in the valence band, indicating strong coupling between the dopants. The hybridized states, located mainly at the edge of the valence band, are composed of anionic dopants 2p states and Re-5d states, while other Ti-3d states are at the edge of the conduction band. Particularly, for (C, Re) pair [see Fig. 3(h)], a large upshift (0.67 eV) of VBM and a tiny downshift of CBM are observed. The net band gap reduction is 0.82 eV relative to that of pure TiO2 . Band-gap narrowing is a highly important factor for the enhancement of optical absorption under visible light irradiation. Since (C, Re), (CN, Re), and (3N, Re)-codoped TiO2 reduce the band gap to a larger extent than the other codoped systems, we calculate their optical properties by the frequency dependence of the dielectric function e(w) = e1 (w) + ie2 (w), which is mainly a function of electronic structure. The imaginary part of the dielectric function, e2 (w), can be calculated from the momentum matrix elements between the occupied and unoccupied wave functions. The real part e1 (w) can be evaluated from the imaginary part e2 (w) by the famous Kramer–Kronig relationship. The corresponding absorption spectrum is estimated using the following equation:

pure TiO2 (C, Re) (CN, Re) (3N, Re)

6 4 2 0

0

1

2 Energy/eV

3

Fig. 4. (color online) Calculated optical adsorption spectra of TiO2 with a complexes of (C, Re), (NC, Re), and (3N, Re), respectively. The optical adsorption spectrum of TiO2 is included for comparison.

4. Conclusion In this paper, according to the first-principles calculations and analysis of electronic structures, we have proposed that the codopings with nonmetal (C or/and N) and transition metal (Re) impurities are used to improve photocatalytic limitation of anatase TiO2 . We find that (C, Re), (CN, Re), and (3N, Re)-codoped systems each could induce a larger band gap reduction than other doped systems. However, for (CN, Re) and (3N, Re) combinations, their high formation energies limit their concentrations under thermal equilibrium. With a relatively low formation energy and a large binding energy, (C, Re) codoping is predicted to be a good candidate for the considerable enhancement of the photocatalytic activity of anatase TiO2 in the visible-light region.

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Chinese Physics B Volume 23

Number 2

February 2014

TOPICAL REVIEW — Magnetism, magnetic materials, and interdisciplinary research 027503

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026801

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027303

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Resonant interaction scheme for GHZ state preparation and quantum phase gate with superconducting qubits in a cavity Liu Xin, Liao Qing-Hong, Fang Guang-Yu, Wang Yue-Yuan and Liu Shu-Tian

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A modified equation of state for Xe at high pressures by molecular dynamics simulation Xiao Hong-Xing and Long Chong-Sheng

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An improved car-following model with consideration of the lateral effect and its feedback control research Zheng Ya-Zhou, Zheng Peng-Jun and Ge Hong-Xia

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Employment of Jacobian elliptic functions for solving problems in nonlinear dynamics of microtubules Slobodan Zekovi´c, Annamalai Muniyappan, Slobodan Zdravkovi´c and Louis Kavitha

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Theoretical study on K , L, and M X-ray transition energies and rates of neptunium and its ions Ismail Abdalla Saber, Dong Chen-Zhong, Wang Xiang-Li, Zhou Wei-Dong and Wu Zhong-Wen

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Control of the photodetachment of H near a metallic sphere surface by an elastic interface Li Shao-Sheng and Wang De-Hua ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS

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Role of shape of hole in transmission and negative refractive index of sandwiched metamaterials Zhong Min and Ye Yong-Hong

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Effects of self-fields on gain in two-stream free electron laser with helical wiggler and an axial guiding magnetic field Saviz S, Lashani E and Ashkarran A

024103

Effect of normalized plasma frequency on electron phase-space orbits in a free-electron laser Ji Yu-Pin, Wang Shi-Jian, Xu Jing-Yue, Xu Yong-Gen, Liu Xiao-Xu, Lu Hong, Huang Xiao-Li and Zhang Shi-Chang

024104

Amplifying device created with isotropic dielectric layer Wang Shen-Yun and Liu Shao-Bin

024201

Design of a tunable frequency selective surface absorber as a loaded receiving antenna array Lin Bao-Qin, Zhao Shang-Hong, Wei Wei, Da Xin-Yu, Zheng Qiu-Rong, Zhang Heng-Yang and Zhu Meng

024202

Single photon transport properties in coupled cavity arrays nonlocally coupled to a two-level atom in the presence of dissipation Hai Lian, Tan Lei, Feng Jin-Shan, Xu Wen-Bin and Wang Bin (Continued on the Bookbinding Inside Back Cover)

024203

Investigation on the intensity noise characteristics of the semiconductor ring laser Kang Ze-Xin, Cai Xin-Lun, Wen Xiao-Dong, Liu Chao, Jian Shui-Sheng and Yu Si-Yuan

024204

Effects of water and ice clouds on cloud microphysical budget: An equilibrium modeling study Gao Shou-Ting, Li Xiao-Fan and Zhou Yu-Shu

024205

Spectroscopic properties and mechanism of Tm3+ /Er3+ /Yb3+ co-doped oxyfluorogermanate glass ceramics containing BaF2 nanocrystals Hu Yue-Bo, Qiu Jian-Bei, Zhou Da-Cheng, Song Zhi-Guo, Yang Zheng-Wen, Wang Rong-Fei, Jiao Qing and

024206

Zhou Da-Li Photon statistical properties of photon-added two-mode squeezed coherent states Xu Xue-Fen, Wang Shuai and Tang Bin

024207

Applications of quantum Fourier transform in photon-added coherent state Ren Gang, Du Jian-Ming and Yu Hai-Jun

024208

Maximal entanglement from photon-added nonlinear coherent states via unitary beam splitters

024209

K. Berrada A compact graphene Q-switched erbium-doped fiber laser using optical circulator and tunable fiber Bragg grating Li He-Ping, Xia Han-Ding, Wang Ze-Gao, Zhang Xiao-Xia, Chen Yuan-Fu, Zhang Shang-Jian, Tang XiongGui and Liu Yong

024210

Evolution of modes in double-clad Raman fiber amplifier Wang Wen-Liang, Huang Liang-Jin, Leng Jin-Yong, Guo Shao-Feng and Jiang Zong-Fu

024211

Beam control in tri-core photonic lattices Ye Zhuo-Yi, Xia Shi-Qiang, Song Dao-Hong, Tang Li-Qin and Lou Ci-Bo

024212

Nonlinear optical properties of an azobenzene polymer Zeng Yi, Pan Zhi-Hua, Zhao Fu-Li, Qin Mu, Zhou Yan and Wang Chang-Shun

024501

On the modeling of synchronized flow in cellular automaton models Jin Cheng-Jie, Wang Wei and Jiang Rui

024701

Heat transfer for boundary layers with cross flow Krishnendu Bhattacharyya and Ioan Pop PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

025201

A thin radar-infrared stealth-compatible structure: Design, fabrication, and characterization Tian Hao, Liu Hai-Tao and Cheng Hai-Feng

025202

Parametric instabilities in single-walled carbon nanotubes He Cai-Xia, Jian Yue, Qi Xiu-Ying and Xue Ju-Kui

025203

Out-of-plane shear flow effects on fast magnetic reconnection in a two-dimensional hybrid simulation model Wang Lin, Wang Xian-Qu, Wang Xiao-Gang and Liu Yue

025204

Mechanical properties of Al/a-C nanocomposite thin films synthesized using a plasma focus device Z. A. Umar, R. S. Rawat, R. Ahmad, A. K. Kumar, Y. Wang, T. Hussain, Z. Chen, L. Shen and Z. Zhang (Continued on the Bookbinding Inside Back Cover)

025205

The combined effect of optical laser and microwave radiations on a metal surface Anatoli P Gavrilyuk and Nikolai Ya Shaparev CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

026101

Effects of annealing process on characteristics of fully transparent zinc tin oxide thin-film transistor Chen Yong-Yue, Wang Xiong, Cai Xi-Kun, Yuan Zi-Jian, Zhu Xia-Ming, Qiu Dong-Jiang and Wu Hui-Zhen

026102

Dielectric and infrared properties of SrTiO3 single crystal doped by 3d (V, Mn, Fe, Ni) and 4f (Nd, Sm, Er) ions S. Maletic, D. Maletic, I. Petronijevic, J. Dojcilovic and D. M. Popovic

026103

New observations on hydrogen bonding in ice by density functional theory simulations Zhang Peng, Liu Yang, Yu Hui, Han Sheng-Hao, L¨u Ying-Bo, L¨u Mao-Shui and Cong Wei-Yan

026104

Effects of cold rolling deformation on microstructure, hardness, and creep behavior of high nitrogen austenitic stainless steel Sun Shi-Cheng, Sun Gui-Xun, Jiang Zhong-Hao, Ji Chang-Tao, Liu Jia-An and Lian Jian-She

026201

Elastic and thermodynamic properties of vanadium nitride under pressure and the effect of metallic bonding on its hardness Pu Chun-Ying, Zhou Da-Wei, Bao Dai-Xiao, Lu Cheng, Jin Xi-Lian, Su Tai-Chao and Zhang Fei-Wu

026301

First-principles study of the structural, elastic, and optical properties for Sr0.5 Ca0.5 TiO3 Yang Chun-Yan and Zhang Rong

026401

Phase transition of Bose–Einstein condensate under decoherence Zheng Qiang, Yi Shan-Feng and Hu Chang-Gang

026402

Subsolidus phase relation in the Bi2 O3 –Fe2 O3 –La2 O3 system Hu Qi-Chang, Chen Ye-Qing, L¨u Pei-Wen, Huang Feng and Wang Xian

026601

Subcooled pool boiling heat transfer in fractal nanofluids: A novel analytical model Xiao Bo-Qi, Yang Yi and Xu Xiao-Fu

026701

Condensation of Fermions in the double-well potential Chen Xin-Wei, Liu Zhong-Qiang and Kong Xiang-Mu

026802

AA bilayer graphene on Si-terminated SiO2 under electric field Liu Hai-Long, Liu Yan, Wang Tao and Ao Zhi-Min CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

027101

Comparison of electrical characteristic between AlN/GaN and AlGaN/GaN heterostructure Schottky diodes L¨u Yuan-Jie, Feng Zhi-Hong, Lin Zhao-Jun, Gu Guo-Dong, Dun Shao-Bo, Yin Jia-Yun, Han Ting-Ting and Cai Shu-Jun (Continued on the Bookbinding Inside Back Cover)

027102

Different influences of Schottky metal on the strain and relative permittivity of barrier layer between AlN/GaN and AlGaN/GaN heterostructure Schottky diodes L¨u Yuan-Jie, Feng Zhi-Hong, Gu Guo-Dong, Dun Shao-Bo, Yin Jia-Yun, Wang Yuan-Gang, Xu Peng, Han Ting-Ting, Song Xu-Bo, Cai Shu-Jun, Luan Chong-Biao and Lin Zhao-Jun

027103

Damage mechanism of hydroxyl radicals toward adenine–thymine base pair Tan Rong-Ri, Wang Dong-Qi and Zhang Feng-Shou

027201

The effect of k -cubic Dresselhaus spin orbit coupling on the decay time of persistent spin helix states in semiconductor two-dimensional electron gases Chai Zheng, Hu Mao-Jin, Wang Rui-Qiang and Hu Liang-Bin

027202

Electronic band gap and transport in graphene superlattice with a Gaussian profile potential voltage Zhang Yu-Ping, Yin Yi-Heng, L¨u Huan-Huan and Zhang Hui-Yun

027301

AlOx prepared by atomic layer deposition for high efficiency-type crystalline silicon solar cell Qiu Hong-Bo, Li Hui-Qi, Liu Bang-Wu, Zhang Xiang and Shen Ze-Nan

027302

Kink effect in current–voltage characteristics of a GaN-based high electron mobility transistor with an AlGaN back barrier Ma Xiao-Hua, L¨u Min, Pang Lei, Jiang Yuan-Qi, Yang Jing-Zhi, Chen Wei-Wei and Liu Xin-Yu

027304

Investigation of the mode splitting induced by electro-optic birefringence in a vertical-cavity surfaceemitting laser bypolarized electroluminescence Zhang Jie, Yu Jin-Ling, Cheng Shu-Ying, Lai Yun-Feng and Chen Yong-Hai

027305

A strategy of enhancing the photoactivity of TiO2 containing nonmetal and transition metal dopants Li Wei, Wei Shi-Hao and Duan Xiang-Mei

027501

Effect of magnetic properties of soft magnetic phase on the energy product of an exchange-spring magnet Jia Li-Ying, Yin Jin-Hua and Ma Xing-Qiao

027502

Ferrimagnetism and metal insulator transition in an organic polymer chain Ding Lin-Jie, Zhong Yuan and Fan Shuai-Wei

027601

High contrast atomic magnetometer based on coherent population trapping Yang Ai-Lin, Yang Guo-Qing, Xu Yun-Fei and Lin Qiang

027701

Resonance-mode effect on piezoelectric microcantilever performance in air, with a focus on the torsional modes Qiu Hua-Cheng, Dara Feili, Wu Xue-Zhong and Helmut Seidel

027702

Asymmetric reversible diode-like resistive switching behaviors in ferroelectric BaTiO3 thin films Zhang Fei, Lin Yuan-Bin, Wu Hao, Miao Qing, Gong Ji-Jun, Chen Ji-Pei, Wu Su-Juan, Zeng Min, Gao XingSen and Liu Jun-Ming

027703

Microscopic degradation mechanism of polyimide film caused by surface discharge under bipolar continuous square impulse voltage Luo Yang, Wu Guang-Ning, Liu Ji-Wu, Peng Jia, Gao Guo-Qiang, Zhu Guang-Ya, Wang Peng and Cao KaiJiang (Continued on the Bookbinding Inside Back Cover)

027801

Red-shift law of intense laser-induced electro-absorption in solids Deng Hong-Xiang, Zu Hao-Yue, Wu Shao-Yi, Sun Kai and Zu Xiao-Tao

027802

A generalized method of converting CT image to PET linear attenuation coefficient distribution in PET/CT imaging Wang Lu, Wu Li-Wei, Wei Le, Gao Juan, Sun Cui-Li, Chai Pei and Li Dao-Wu

027803

Optimization of InAs/GaAs quantum-dot structures and application to 1.3-µm mode-locked laser diodes Li Mi-Feng, Ni Hai-Qiao, Ding Ying, Bajek David, Kong Liang, Cataluna Maria Ana and Niu Zhi-Chuan

027804

Numerical demonstration of three-dimensional terahertz metamaterials based on the causality principle Saeid Jamilan, Javad Nourinia and Mohammad Naghi Azarmanesh INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

028101

Occurrence and elimination of in-plane misoriented crystals in AlN epilayers on sapphire via pretreatment control Wang Hu, Xiong Hui, Wu Zhi-Hao, Yu Chen-Hui, Tian Yu, Dai Jiang-Nan, Fang Yan-Yan, Zhang Jian-Bao and Chen Chang-Qing

028102

Controlled construction of nanostructures in graphene Li Zhong-Jun, Li Qiang, Cheng Zeng-Guang, Li Hong-Bian and Fang Ying

028103

Transparent conductive graphene films prepared by hydroiodic acid and thermal reduction Qin Meng-Meng, Ji Wei, Feng Yi-Yu and Feng Wei

028201

Microstructure and its influence on CH4 adsorption behavior of deep coal Feng Yan-Yan, Jiang Cheng-Fa, Liu Dai-Jun and Chu Wei

028401

Study of a millimeter-wave squint indirect holographic algorithm suitable for imaging with large fieldof-view Gao Xiang, Li Chao and Fang Guang-You

028501

Impact of multiplexed reading scheme on nanocrossbar memristor memory’s scalability Zhu Xuan, Tang Yu-Hua, Wu Chun-Qing, Wu Jun-Jie and Yi Xun

028502

Performance improvement of GaN-based light-emitting diode with a p-InAlGaN hole injection layer Yu Xiao-Peng, Fan Guang-Han, Ding Bin-Bin, Xiong Jian-Yong, Xiao Yao, Zhang Tao and Zheng Shu-Wen

028503

Influences of polarization effect and p-region doping concentration on the photocurrent response of solar-blind p i n avalanche photodiodes Li Xiao-Jing, Zhao De-Gang, Jiang De-Sheng, Liu Zong-Shun, Chen Ping, Wu Liang-Liang, Li Liang, Le Ling-Cong, Yang Jing, He Xiao-Guang, Wang Hui, Zhu Jian-Jun, Zhang Shu-Ming, Zhang Bao-Shun and Yang Hui

028504

Large-scale SiO2 photonic crystal for high efficiency GaN LEDs by nanospherical-lens lithography Wu Kui, Wei Tong-Bo, Lan Ding, Zheng Hai-Yang, Wang Jun-Xi, Luo Yi and Li Jin-Min

028505

A novel strong green phosphor: K3 Gd(PO4 )2 :Ce3+ , Tb3+ for a UV-excited white light-emitting-diode Jiang Ting-Ming, Yu Xue, Xu Xu-Hui, Zhou Da-Cheng, Yu Hong-Ling, Yang Peng-Hui and Qiu Jian-Bei (Continued on the Bookbinding Inside Back Cover)

028701

Bifurcation diagram globally underpinning neuronal firing behaviors modified by SK conductance Chen Meng-Jiao, Ling Heng-Li, Liu Yi-Hui, Qu Shi-Xian and Ren Wei

028702

Application of radial basis functions to evolution equations arising in image segmentation Li Shu-Ling and Li Xiao-Lin

028703

Multi-objective optimization of gradient coil for benchtop magnetic resonance imaging system with highresolution Wang Long-Qing and Wang Wei-Min

028801

Analysis of each branch current of serial solar cells by using an equivalent circuit model Yi Shi-Guang, Zhang Wan-Hui, Ai Bin, Song Jing-Wei and Shen Hui

028802

Hybrid solar cell based on polythiophene and GaN nanoparticles composite Feng Qian, Shi Peng, Li Yu-Kun, Du Kai, Wang Qiang, Feng Qing and Hao Yue

028803

Modified-DBR-based semi-omnidirectional multilayer anti-reflection coating for tandem solar cells Ali Bahrami, Shahram Mohammadnejad and Nima Jouyandeh Abkenar

028901

Generation of minimally persistent circle formation for a multi-agent system Luo Xiao-Yuan, Shao Shi-Kai, Zhang Yu-Yan, Li Shao-Bao, Guan Xin-Ping and Liu Zhi-Xin

028902

Optimal network structure to induce the maximal small-world effect Zhang Zheng-Zhen, Xu Wen-Jun, Zeng Shang-You and Lin Jia-Ru

028903

MDSLB: A new static load balancing method for parallel molecular dynamics simulations Wu Yun-Long, Xu Xin-Hai, Yang Xue-Jun, Zou Shun and Ren Xiao-Guang

028904

Analyzing the causation of a railway accident based on a complex network Ma Xin, Li Ke-Ping, Luo Zi-Yan and Zhou Jin GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS

029201

Improvement of surface flux calculation: A study based on measurements over alpine meadow in the eastern Tibet Plateau in summer Li Sen and Zhong Zhong

029202

Vertical structure of predictability and information transport over the Northern Hemisphere Feng Ai-Xia, Wang Qi-Gang, Gong Zhi-Qiang and Feng Guo-Lin