SrCoO_(3-x)薄膜中氧空位引起的电子结构演变（英文）
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摘要
离子缺陷,比如氧空位,在过渡金属氧化物的磁性和电子结构中起着至关重要的作用.对氧空位进行调控广泛应用于催化和能量转换领域.我们研究了SrCoO_(3-x)的电子结构与氧含量x的关系,发现随着氧空位含量的减少, Co 3d和O 2p之间的杂化增强.SrCoO_(2.5+δ)的价带顶具有明显的O 2p特征.随着氧含量的进一步增加, Co离子从高自旋的Co~(3+)变成了中自旋的Co~(4+),实现了绝缘体到金属的转变.关于SrCoO_(3-x)中氧空位引起电子结构演变的研究不仅展示了Co离子自旋的转变,同时也为其在催化和能源领域的应用提供了理论支持.
Ionic defects, such as oxygen vacancies, play a crucial role in the magnetic and electronic states of transition metal oxides. Control of oxygen vacancy is beneficial to the technological applications, such as catalysis and energy conversion. Here, we investigate the electronic structure of SrCoO_(3-x) as a function of oxygen content(x). We found that the hybridization extent between Co 3d and O 2p increased with the reduction of oxygen vacancies. The valence band maximum of SrCoO_(2.5+δ) has a typical O 2p characteristic. With further increasing oxygen content, the Co ions transform from a high spin Co~(3+) to an intermediate spin Co~(4+), resulting in a transition of SrCoO_(3-x) from insulator to metal. Our results on the electronic structure evolution with the oxygen vacancies in SrCoO_(3-x) not only illustrate a spin state transition of Co ions,but also indicate a perspective application in catalysis and energy field.
Ionic defects, such as oxygen vacancies, play a crucial role in the magnetic and electronic states of transition metal oxides. Control of oxygen vacancy is beneficial to the technological applications, such as catalysis and energy conversion. Here, we investigate the electronic structure of SrCoO_(3-x) as a function of oxygen content(x). We found that the hybridization extent between Co 3d and O 2p increased with the reduction of oxygen vacancies. The valence band maximum of SrCoO_(2.5+δ) has a typical O 2p characteristic. With further increasing oxygen content, the Co ions transform from a high spin Co~(3+) to an intermediate spin Co~(4+), resulting in a transition of SrCoO_(3-x) from insulator to metal. Our results on the electronic structure evolution with the oxygen vacancies in SrCoO_(3-x) not only illustrate a spin state transition of Co ions,but also indicate a perspective application in catalysis and energy field.
引文
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18 Long Y,Kaneko Y,Ishiwata S,et al.Synthesis of cubic SrCoO3single crystal and its anisotropic magnetic and transport properties.J Phys-Condens Matter,2011,23:245601
19 Lee JH,Rabe KM.Coupled magnetic-ferroelectric metal-insulator transition in epitaxially strained SrCoO3from first principles.Phys Rev Lett,2011,107:067601
20 Potze RH,Sawatzky GA,Abbate M.Possibility for an intermediate-spin ground state in the charge-transfer material SrCoO3.Phys Rev B,1995,51:11501-11506
21 Zhuang M,Zhang W,Hu A,et al.Possible magnetic ground state in the perovskite SrCoO3.Phys Rev B,1998,57:13655-13659
22 Karvonen L,Valkeapaa M,Liu RS,et al.O-K and Co-L XANESstudy on oxygen intercalation in perovskite SrCoO3-δ.Chem Mater,2010,22:70-76
2 Lu S,Zhuang Z.Electrocatalysts for hydrogen oxidation and evolution reactions.Sci China Mater,2016,59:217-238
3 Kalinin SV,Spaldin NA.Functional ion defects in transition metal oxides.Science,2013,341:858-859
4 Lan QQ,Zhang XJ,Shen X,et al.Tuning the magnetism of epitaxial cobalt oxide thin films by electron beam irradiation.Phys Rev Mater,2017,1:024403
5 Xie CK,Nie YF,Wells BO,et al.Magnetic phase separation in SrCoOx(2.5≤x≤3).Appl Phys Lett,2011,99:052503
6 Choi WS,Jeen H,Lee JH,et al.Reversal of the lattice structure in SrCoOxepitaxial thin films studied by real-time optical spectroscopy and first-principles calculations.Phys Rev Lett,2013,111:097401
7 Jeen H,Choi WS,Biegalski MD,et al.Reversible redox reactions in an epitaxially stabilized SrCoOxoxygen sponge.Nat Mater,2013,12:1057-1063
8 Jeen H,Choi WS,Freeland JW,et al.Topotactic phase transformation of the brownmillerite SrCoO2.5to the perovskite SrCoO3-δ.Adv Mater,2013,25:3651-3656
9 Lee JH,Choi WS,Jeen H,et al.Strongly coupled magnetic and electronic transitions in multivalent strontium cobaltites.Sci Rep,2017,7:16066
10 Zhu ZH,Rueckert FJ,Budnick JI,et al.Distinct magnetic phases in structurally uniform SrCoO3-y.Phys Rev B,2016,93:224412
11 Hu S,Seidel J.Oxygen content modulation by nanoscale chemical and electrical patterning in epitaxial SrCoO3-δ(0<δ≤0.5)thin films.Nanotechnology,2016,27:325301
12 Zhang KHL,Sushko PV,Colby R,et al.Reversible nano-structuring of SrCrO3-δthrough oxidation and reduction at low temperature.Nat Commun,2014,5:4669
13 Lu N,Zhang P,Zhang Q,et al.Electric-field control of tri-state phase transformation with a selective dual-ion switch.Nature,2017,546:124-128
14 Lu Q,Chen Y,Bluhm H,et al.Electronic structure evolution of SrCoOxduring electrochemically driven phase transition probed by in situ X-ray spectroscopy.J Phys Chem C,2016,120:24148-24157
15 Lim J,Yu J.Role of oxygen vacancy in the spin-state change and magnetic ordering in SrCoO3-δ.Phys Rev B,2018,98:085106
16 Zhao J,Guo H,He X,et al.Manipulating the structural and electronic properties of epitaxial SrCoO2.5thin films by tuning the epitaxial strain.ACS Appl Mater Interfaces,2018,10:10211-10219
17 Zhang Q,He X,Shi J,et al.Atomic-resolution imaging of electrically induced oxygen vacancy migration and phase transformation in SrCoO2.5-σ.Nat Commun,2017,8:104
18 Long Y,Kaneko Y,Ishiwata S,et al.Synthesis of cubic SrCoO3single crystal and its anisotropic magnetic and transport properties.J Phys-Condens Matter,2011,23:245601
19 Lee JH,Rabe KM.Coupled magnetic-ferroelectric metal-insulator transition in epitaxially strained SrCoO3from first principles.Phys Rev Lett,2011,107:067601
20 Potze RH,Sawatzky GA,Abbate M.Possibility for an intermediate-spin ground state in the charge-transfer material SrCoO3.Phys Rev B,1995,51:11501-11506
21 Zhuang M,Zhang W,Hu A,et al.Possible magnetic ground state in the perovskite SrCoO3.Phys Rev B,1998,57:13655-13659
22 Karvonen L,Valkeapaa M,Liu RS,et al.O-K and Co-L XANESstudy on oxygen intercalation in perovskite SrCoO3-δ.Chem Mater,2010,22:70-76