Acta Phys. -Chim. Sin. ›› 2018, Vol. 34 ›› Issue (12): 1373-1380.doi: 10.3866/PKU.WHXB201804131

Special Issue: Surface Physical Chemistry

• ARTICLE • Previous Articles     Next Articles

Growth of Ordered ZnO Structures on Au(111) and Cu(111)

Xinfei ZHAO1,2,Hao CHEN1,2,Hao WU1,3,Rui WANG4,5,Yi CUI4,Qiang FU1,Fan YANG1,*(),Xinhe BAO1   

  1. 1 State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning Province, P. R. China
    2 University of Chinese Academy of Sciences, Beijing 100049, P. R. China
    3 Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, P. R. China
    4 Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, Jiangsu Province, P. R. China
    5 Nano Science and Technology Institute, University of Science and Technology of China, Suzhou 215123, Jiangsu Province, P. R. China
  • Received:2018-03-15 Published:2018-04-27
  • Contact: Fan YANG E-mail:fyang@dicp.ac.cn
  • Supported by:
    The project was supported by the Ministry of Science and Technology of China(2017YFB0602205);The project was supported by the Ministry of Science and Technology of China(2016YFA0202803);the National Natural Science Foundation of China(21473191);the National Natural Science Foundation of China(91545204);the Thousand Talents Program for Young Scientists

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Abstract:

The growth and structural properties of ZnO thin films on both Au(111) and Cu(111) surfaces were studied using either NO2 or O2 as oxidizing agent. The results indicate that NO2 promotes the formation of well-ordered ZnO thin films on both Au(111) and Cu(111). The stoichiometric ZnO thin films obtained on these two surfaces exhibit a flattened and non-polar ZnO(0001) structure. It is shown that on Au(111), the growth of bilayer ZnO nanostructures (NSs) is favored during the deposition of Zn in presence of NO2 at 300 K, whereas both monolayer and bilayer ZnO NSs could be observed when Zn is deposited at elevated temperatures under a NO2 atmosphere. The growth of bilayer ZnO NSs is caused by the stronger interaction between two ZnO layers than between ZnO and Au(111) surface. In contrast, the growth of monolayer ZnO NSs involves a kinetically controlled process. ZnO thin films covering the Au(111) surface exhibits a multilayer thickness, which is consistent with the growth kinetics of ZnO NSs. Besides, the use of O2 as oxidizing agent could lead to the formation of sub-stoichiometric ZnOx structures. The growth of full layers of ZnO on Cu(111) has been a difficult task, mainly because of the interdiffusion of Zn promoted by the strong interaction between Cu and Zn and the formation of Cu surface oxides by the oxidation of Cu(111). We overcome this problem by using NO2 as oxidizing agent to form well-ordered ZnO thin films covering the Cu(111) surface. The surface of the well-ordered ZnO thin films on Cu(111) displays mainly a moiré pattern, which suggests a (3 × 3) ZnO superlattice supported on a (4 × 4) supercell of Cu(111). The observation of this superstructure provides a direct experimental evidence for the recently proposed structural model of ZnO on Cu(111), which suggests that this superstructure exhibits the minimal strain. Our studies suggested that the surface structures of ZnO thin films could change depending on the oxidation level or the oxidant used. The oxidation of Cu(111) could also become a key factor for the growth of ZnO. When Cu(111) is pre-oxidized to form copper surface oxides, the growth mode of ZnOx is altered and single-site Zn could be confined into the lattice of copper surface oxides. Our studies show that the growth of ZnO is promoted by inhibiting the diffusion of Zn into metal substrates and preventing the formation of sub-stoichiometric ZnOx. In short, the use of an atomic oxygen source is advantageous to the growth of ZnO thin films on Au(111) and Cu(111) surfaces.

Key words: ZnO/Au(111), ZnO/Cu(111), STM, XPS, Model catalysis