ZnO(0001) 极性面的第一性原理计算研究

表面性质对理解表面化学反应具有关键性的作用，尤其是二维材料的表面性
质受到格外关注。部分这类材料具有“极性面”的结构，对于具有这类结构的材
料，通常会伴随着重构现象的发现，探索重构结构和理解相关机理具有一定的科学研究意义。一个典型的具有极性面特征的材料是宽带隙透明导电氧化物材料 ZnO，此材料在光电、发光器件、催化和气体传感器等众多领域有广泛应用。尽管目前对 ZnO 极性面的稳定重构模型的研究较为成熟，但已有报道中对于这一类问题尚未有统一自洽的解释。为寻找稳定的 ZnO(0001) 面重构结构和稳定机制，本论文采用第一性原理计算方法，在电荷补偿机制下系统研究 ZnO(0001) 面不同结构模型的表面能，寻找稳定的极性面重构结构并分析稳定机制。
ZnO(0001) 面的研究从单层重构开始，研究分析表面形成不同数量的 Zn 空位
和 O 吸附的时候表面能的变化及原因，解释 Zn 空位和 O 吸附的稳定构型是局部
有序的亚稳态结构；分析三角空腔形成是静电马德隆力驱动主导，构建存在三角空腔和 O 吸附的 ADC 结构模型。因静电马德隆力不是唯一的三角空腔驱动力，并且吸附原子的过程具有随机性，发现如 n3(+6O)，2n3(+3O)，2n2(+5O) 等结构比 ADC结构相对表面能更低。此外我们另辟蹊径，研究 ZnO(0001) 面的多层重构，研究双层三角空腔结构和 n7 结构，发现新的稳定结构模型，如 n6n3(201)，n7n3(101)，n7n3(011)，n7n3(020) 等结构，尤其 n7n3(011)、n7n3(020) 和 n7(05) 等结构比同 slab大小的 ADC 结构的相对能量低了约 1eV 以上。这些结构的发现，证明极性面结构中，表面欠配位 Zn 离子浓度对其结构稳定性起主要作用，此外内层重构也会影响极性面的稳定性。在贫 H 富 O 条件下，得到大范围内稳定存在的结构是 n7(05) 结构。
 

A key factor which influences the surface chemical reactions, especially the ones occur at two-dimensional materials is the surface proper. Some of these materials have ”polarsurface”structures. Formaterialswithsuchstructures, thediscoveryofreconstruc-
tion phenomenon isusuallyaccompanied. It is of certain scientific significance to explore the reconstruction structure and understand the relevant mechanism. A typical material with polar surface characteristics is ZnO, a wide-gap transparent conductive oxide mate-rial, which is widely used in many fields such as optoelectronics, light-emitting devices,
catalysis and gas sensors. Although the research on the stable reconstruction model of ZnO polarity plane is relatively mature, there is no unified self-consistent explanation for this kind of problem in the existing reports. In order to find the stable ZnO(0001) sur-face reconstruction structure and stabilization mechanism, the surface energy of different
ZnO(0001) surface structure models under charge compensation mechanism is system-atically studied by first-principles calculation method. The stable polar surface recon-struction structure of ZnO(0001) surface is searched and the stabilization mechanism is analyzed.
The study of ZnO(0001) surface began with monolayer reconstruction, and analyzed the changes of surface energy and the reasons for the formation of different number of Zn vacancies and O adsorption on the surface, explaining that the stable configuration of Zn vacancies and O adsorption is a locally ordered metastable structure. The formation of
triangular cavity was analyzed to be driven by electrostatic Madelung force, and the ADC structural model with triangular cavity and O adsorption was constructed. Because the electrostatic Madelung force is not the only driving force of the triangular cavity, and the
process of absorbing atoms is random, it is found that the relative surface energy of struc-tures such as n3(+6O), 2n3(+3O) and 2n2(+5O) is lower than that of the ADC model. In addition, we tried to study the multilayer reconstruction of ZnO(0001) plane, study the double-layer triangular cavity structure and n7 structure, and find new stable structure
models, such as n6n3(201), n7n3(101), n7n3(011), n7n3(020), etc. In particular, the rel-ative energy of n7n3(011), n7n3(020) and n7(05) structures is more than 1eV lower than that of ADC structures of the same slab size. The discovery of these structures proves that
the surface undercoordination concentration of Zn ions plays a major role in the stability of polar plane structures, and the inner layer reconstruction also affects the stability of polar plane structures. The n7(05) structure is stable in a wide range under H - poor and O - rich conditions.
 

[1] LI C C, ZHOU H G, YANG S C, et al. pre-adsorption of O2 on the exposed (001) facets ofzno nanostructures for enhanced sensing of gaseous acetone[J]. ACS Applied Nano Materials,2019, 2(10):6144-6151.
[2] YUMS,WANGGC,ZHAORR,etal. ImprovedinterfacialwetabilityinCu/ZnOanditsroleinZnO/Cu/ZnO sandwiched transparent electrodes[J]. Journal of Materials Science Technology,2020, 37:123-127.
[3] LI B J , WEI S, LIAO C H, et al. High-mobility ZnVxOy/ZnO conduction path in ZnO/V/ZnOmultilayer structure[J]. Journal of Applied Physics, 2020, 130:075302.
[4] NIE M, SUN H, CAI H L, et al. Study on electrocatalytic property of ZnO and Ag/ZnO[J].Materials Letters, 2020, 271:127785.
[5] RABELL H O, ALFAROCRUZ M R, RAMIREZ J, I. Hydrogen production of ZnO andZnO/Ag films by photocatalysis and photoelectrocatalysis[J]. Materials Science in Semicon-ductor Processing, 2021, 134:105985.
[6] BARADARAN M, GHODSI F E, BITTENCOURT C, et al. The role of Al concentration onimproving the photocatalytic performance of nanostructured ZnO/ZnO:Al/ZnO multilayer thinfilms[J]. Journal of Alloys and Compounds, 2019, 788:289-301.
[7] OU R Z, ZENG Z X, NING X T, et al. Improved photocatalytic performance of N-doped ZnO/graphene/ZnO sandwich composites[J]. Applied Surface Science, 2021, 577:151856.
[8] GOKTAS A, MODANLI S, TUMBUL A, et al. Facile synthesis and characterization of ZnO,ZnO:Co, and ZnO/ZnO:Co nano rod-like homojunction thin films: Role of crystallite/grain sizeandmicrostraininphotocatalyticperformance[J]. JournalofAlloysandCompounds,2021,893:162334.
[9] NAZ F, SAEED K. Investigation of photocatalytic behavior of undoped ZnO and Cr-dopedZnO nanoparticles for the degradation of dye[J]. Inorganic and Nano-Metal Chemistry, 2020,51(25):1-11.
[10] TSAI Y S, CHEN J R, LEE C H, et al. Morphologies and material properties of ZnO nanotubes,ZnO/ZnS core-shell nanorods, and ZnO/ZnS core-shell nanotubes[J]. Ceramics International,2021, 48(5):7232-7239.
[11] SUDHEER V R, SARATHKUMAR S R, SANKARARAMAN S. Nanostructured ZnO andZnO: Pd with MXene overlayer SPR biosensors[J]. Optical and Quantum Electronics, 2021, 53(6):340.
[12] QUE M L, LIN C, SUN J W, et al. Progress in ZnO nanosensors[J]. Sensors, 2021, 21(16):5502.
[13] SON D, MOON B, LEE A, et al. Polarity effects of ZnO on charge recombination at CsPbBr3nanoparticles/ZnO interfaces[J]. Applied Surface Science, 2019, 483:165-169.
[14] SIKAM P, THIRAYATORN R, MOONTRAGOON P, et al. The quantum confined stark effectin N-doped ZnO/ZnO/N-doped ZnO nanostructures for infrared and terahertz applications[J].Nanotechnology, 2020, 31(44):445207.
[15] YANGL, DINGR,ZHUW, et al. ZnOdefectsinvolved in energytransferfor ZnO:Tb nanopar-ticles[J]. Journal of Physics and Chemistry of Solids, 2021, 157:110158.
[16] SARMA B, SARMA B K. Role of residual stress and texture of ZnO nanocrystals on electro-optical properties of ZnO/Ag/ZnO multilayer transparent conductors[J]. Journal of Alloys andCompounds, 2018, 734:210-219.
[17] CHEN Z, YAN Q, ZHAO Y, et al. The structure and the optical-electrical properties of theZnO films and the Al:ZnO/N: ZnO homojunction photodiode[J]. Journal of Sol-Gel Scienceand Technology, 2019, 91:101-110.
[18] GOZEH B A, KARABULUT A, AMEEN M M, et al. Synthesis and characterization of La-doped ZnO (La:ZnO) films for photodetectors[J]. Surface Review and Letters (SRL), 2020, 27(07):1950173.
[19] LI L, YAO C, WU L, et al. ZnS covering of ZnO nanorods for enhancing UV emission fromZnO[J]. The Journal of Physical Chemistry C, 2021, 125:13732-13740.
[20] KIM H W, BAEK S H, LEE S N. Surface plasmon‐enhanced high‐performance ZnO/Ni/ZnOultravioletphotodetectors[J]. PhysicalStatusSolidi-RapidResearchLetters,2021, 14:1900685.
[21] LUPAN O, GUERIN V M, TIGINYANU I M, et al. Well-aligned arrays of vertically orientedZnO nanowires electrodeposited on ITO-coated glass and their integration in dye sensitizedsolar cells[J]. Journal of Photochemistry and Photobiology A: Chemistry, 2010, 211(1):65-73.
[22] SUN X W, WANG L D, KWOK H S. Improved ITO thin films with a thin ZnO buffer layer bysputtering[J]. Thin Solid Films, 2000, 360(1):75-81.
[23] CHANG J, KUO H H, LEU I C, et al. The effects of thickness and operation temperature onZnO:Al thin film CO gas sensor[J]. Sensors and Actuators B: Chemical, 2002, 84(2):258-264.
[24] MITRA P, CHATTERJEE A P, MAITI H S. ZnO thin film sensor[J]. Materials Letters, 1998,35(1):33-38.
[25] LOOK D C. Recent advances in ZnO materials and devices[J]. Materials Science and Engi-neering: B, 2001, 80(1):383-387.
[26] SHAIKH S K, INAMDAR S I, GANBAVLE V V, et al. Chemical bath deposited ZnO thin filmbased UV photoconductive detector[J]. Journal of Alloys Compounds, 2015, 664:242-249.
[27] BORUAHBD,MUKHERJEEA,MISRAA. SandwichedassemblyofZnOnanowiresbetweengraphene layers for a self-powered and fast responsive ultraviolet photodetector[J]. Nanotech-nology, 2016, 27(9):095205.
[28] WU B, WEI S Z, CHI C, et al. The growth of ZnO on stainless steel foils by MOCVD andits application in light emitting devices[J]. Physical Chemistry Chemical Physics, 2016, 18(7):5614-5621.
[29] SOCI C, ZHANG A, XIANG B, et al. ZnO nanowire UV photodetectors with high internalgain.[J]. Nano Letters, 2007, 74(4):1003-1009.
[30] HUANG M H, MAO S, FEICK H, et al. Room-temperature ultraviolet nanowire nanolasers[J].Science, 2001, 292(5523):1897-1899.
[31] WANG W Z, ZENG B Q, YANG J, et al. Aligned ultralong ZnO nanobelts and their enhancedfield emission[J]. Advanced Materials, 2006, 18(24):3275-3278.
[32] YANG Q, GUO X, WANG W, et al. Enhancing sensitivity of a single ZnO Micro-/Nanowirephotodetector by piezo-phototronic effect[J]. ACS Nano, 2010, 4(10):6285-6291.
[33] WAHL R, LAURITSEN J V, BESENBACHER F, et al. Stabilization mechanism for the polarZnO (000-1)-O surface[J]. Physical review. B, 2013, 87(8):085313.
[34] REEBER R R. Lattice parameters of ZnO from 4.2 to 296 K[J]. Journal of Applied Physics,1970, 41(13):5063-5066.
[35] DULUB O, DIEBOLD U, KRESSE G. Novel stabilization mechanism on polar surfaces:ZnO(0001)-Zn[J]. Physical Review Letters, 2003, 90(1):016102.
[36] LAURITSEN J V, PORSGAARD S, KRESSE G. Stabilization principles for polar surfaces ofZnO[J]. ACS Nano, 2011, 5(7):5987-5994.
[37] OEZGUER U, ALIVOV Y I, LIU C, et al. A comprehensive review of ZnO materials anddevices[J]. Journal of Applied Physics, 2005, 98(4):041301.
[38] PEARTON S. Recent progress in processing and properties of ZnO[J]. Progress in MaterialsScience, 2005, 50(3):293-340.
[39] NOGUERA C. Polar oxide surfaces[J]. Journal of Physics: Condensed Matter, 2000, 12(31):R367.
[40] LI Y Y, YU H, YANG Y, et al. Fabrication of 3D ordered mesoporous ball-flower structuresZnO material with the excellent gas sensitive property[J]. Sensors and Actuators B: Chemical,2019, 300:127050.
[41] TASKER P W. The stability of ionic crystal surfaces[J]. Journal of Physics C:Solid StatePhysics, 1979, 12:4977-4984.
[42] NOSKER R W, MARK P, LEVINE J D. Polar surfaces of wurtzite and zincblende lattices[J].Surface Science, 1970, 19:291-317.
[43] STAEMMLER V, FINK K, MEYER B, et al. Stabilization of polar ZnO surfaces: Validatingmicroscopic models by using CO as a probe molecule[J]. Physical Review Letters, 2003, 90(10):106102.
[44] PASHLEY M D. Electron counting model and its application to island structures on molecular-beam epitaxy grown GaAs(001) and ZnSe(001)[J]. Physical Review B, 1989, 40(15):10481-10487.
[45] DU M H, ZHANG S B, NORTHRUP J E, et al. Stabilization mechanisms of polar surfaces:ZnO surfaces[J]. Physical Review B, 2008, 78:155424.
[46] XU H, DONG L, SHI X Q, et al. Stabilizing forces acting on ZnO polar surfaces: STM, LEED,and DFT[J]. Physical Review B, 2014, 89(23):235403.
[47] ZHENGH,GRUYTERSM,PEHLKEE,etal. ”magic”vicinalzincoxidesurfaces[J]. PhysicalReview Letters, 2013, 111(8):086101.
[48] MEYER B, MARX D. Density-functional study of the structure and stability of ZnO surfaces[J]. Physical Review B, 2003, 67(3):035403.
[49] TORBRUGGE S, OSTENDORF F, REICHLING M. Stabilization of zinc-terminatedZnO(0001) by a modified surface stoichiometry[J]. The Journal of Physical Chemistry C, 2009,113(12):4909–4914.
[50] KRESSE G, DULUB O, DIEBOLD U. Competing stabilization mechanism for the polarZnO(0001)-Zn surface[J]. Physical Review B, 2003, 68(24):245409.
[51] XU H, DONG L, SHI X, et al. Observation and analysis of ordered and disordered structureson the ZnO(0001) polar surface[J]. Journal of Physical Chemistry C, 2016, 120:26915-26921.
[52] LIU Y, XU W, SHAN Y, et al. High reactivity of the ZnO(0001) polar surface: The role ofoxygen adatoms[J]. J. Phys. Chem. C, 2017, 121(29):15711-15718.
[53] VALTINER M, TODOROVA M, GRUNDMEIER G, et al. Temperature stabilized surfacereconstructions at polar ZnO(0001)[J]. Physical Review Letters, 2009, 103(6):065502.
[54] YOO S H, TODOROVA M, NEUGEBAUER J. Selective solvent-induced stabilization of po-lar oxide surfaces in an electrochemical environment[J]. Physical Review Letters, 2018, 120:066101.
[55] MEYER B. First-principles study of the polar O-terminated ZnO surface in thermodynamicequilibrium with oxygen and hydrogen[J]. Physical Review B, 2004, 69(4):045416.
[56] PRUZAN P, LIEBENBERG D H, MILLS R L. Approach to melting in ammonia as a criticaltransition[J]. Physical Review Letters, 1982, 48:1200-1203.
[57] BORNM,OPPENHEIMERR. Zurquantentheoriedermolekeln[J]. AnnalenDerPhysik,1985,389(20):457-484.
[58] KOHN W, SHAM L J. Quantum density oscillations in an inhomogeneous electron gas[J].Physical Review, 1965, 137(6A):1697.
[59] FOCK V. Naherungsmethode zur losung des quantenmechanischen mehrkorperproblems[J].Zeitschrift Fur Physik, 1930, 61(1-2):126-148.
[60] KOHN W, SHAM L J. Self-consistentequations including exchange and correlation effects,DFT[J]. Physical Review, 1965, 140(4A):1133.
[61] CEPERLEY D M, ALDER B J. Ground state of the electron gas by a stochastic method[J].Physical Review Letters, 1980, 45:566–569.
[62] BURKE K, PERDEW J P, YUE W. Derivation of a generalized gradient approximation: ThePW91 density functional[J]. Springer US, 1998.
[63] PERDEW J P, BURKE K, ERNZERHOF M. Generalized gradient approximation made simple[J]. Physical Review Letters, 1996, 77(18):3865-3868.
[64] VANDERBILT D. Soft self-consistent pseudopotentials in a generalized eigenvalue formalism[J]. Physical Review B, 1990, 41(11):7892-7895.
[65] SUN G, KüRTI J, RAJCZY P, et al. Performance of the vienna ab initio simulation package(VASP) in chemical applications[J]. Journal of Molecular Structure Theochem, 2015, 624(1-3):37-45.
[66] HENKELMAN G, UBERUAGA B P, JONSSON H. A climbing image nudged elastic bandmethod for finding saddle points and minimum energy paths[J]. The Journal of ChemicalPhysics, 2000, 113(22):9901-9904.
[67] CHANG S C, MARK P. The crystallography of the polar (0001) Zn and (0001)O surfaces ofzinc oxide[J]. Surface Science, 1974, 46:293-300.
[68] BECKER T, HöVEL S, KUNAT M, et al. Interaction of hydrogen with metal oxides: the caseof the polar ZnO(0001) surface[J]. Surface Science, 2001, 486(3):L502-L506.
[69] VALTINER M, BORODIN S, GRUNDMEIER G. Stabilization and acidic dissolution mecha-nism of single-crystalline ZnO(0001) surfaces in electrolytes studied by in-situ AFM imagingand ex-situ LEED[J]. Langmuir, 2008, 24(10):5350-5358.