Structure and interfacial properties investigation for ZnO/graphene interface

https://doi.org/10.1016/j.matchemphys.2019.02.083Get rights and content

Highlights

  • The Interfacial properties of ZnO–graphene is explored.

  • We find the interlayer van der Waals interaction has a big significant influence.

  • We detect some fantastic phenomena ZnO–graphene interface structure.

  • The interfacial configuration of O-graphene is more stable.

  • The ZnO–graphene interface has the potential for electronic device applications.

Abstract

Interfacial properties of ZnO–graphene were studied through first principles based on density functional theory calculations in this paper. Considering Oxygen polar surface (0001¯) and zinc polar surface(0001) along ZnO's preferred growth direction, three types of interfacial configuration of O-graphene and Zn-graphene were constructed respectively. We investigated the interface binding energies, mechanical, interface structure and electronic properties of ZnO–graphene. The interfacial properties all can illustrate the contact between ZnO and graphene held together by van der Waals forces. Moreover, the interface binding energies exhibit the most stable interface structure and confirm the interfacial configuration of O-graphene is more stable. With interface distance ranges from 1 Å to 5 Å, the interface repulsion force is translated into attractive and slowly tends to zero. The interface structures demonstrate that O atoms are more likely to interact with C atoms, the electronic properties show charge transfer occur on graphene surface at the interface distance of 1.8 Å, with interface distance continue to decrease, the Csingle bondO bond become more tightly and charge transfer between surface O atoms and graphene sufficiently.

Introduction

Zinc oxide is an old and novel oxide material because of good properties of mechanical-electrical coupling, photoelectricity and stability etc [[1], [2], [3]]. Recently, with graphene being successfully prepared and popularized [[4], [5], [6]], the ZnO-graphene(Z-G) have been proved to be an interesting nanocomposites for its excellent performance [[7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18]], such as enhanced photocatalytic behavior [7,8], strong UV, visible photoluminescence and enhanced photoconductivity [[9], [10], [11]], highly efficient and stable field emission [12], bio-functionalization [13,14], and applied in many fields. So many researchers studied Z-G nanocomposites in different aspects. Guo X et al. [17] constructed three interface configurations of Z-G using density functional theory to study band gaps of graphene on layered ZnO, the results showed the band gap of graphene improved along with decrease of interfacial spacing. Hu W et al. [18] studied the electronic and optical properties of Z-G based on density functional theory, they found the Z-G combined by van der Waals forces, and there was no charge transfer between Z-G. Yao Q et al. [19] demonstrated the Z-G exhibits better optical properties. Three types of Z-G composites were built using density functional theory and their properties were investigated under the external electric fields [20], the results showed that there was also a strong link between binding energies, charge transfer and electric field, but the band gaps were hardly affected by the external electric field. Larson K et al. [21] used wurtzite ZnO(110), (100), (001) and hydrogenated graphene to design the Z-G interfacial configuration based on density functional theory, the calculation showed the binding strength had sensitive dependence on the surface orientation. So far, some investigations have been conducted about Z-G interfacial properties, however, the graphite like ZnO [[17], [18], [19]] is hard to realize at current stage and future longer period look, and the monolayer is not stable, there have not been any studies on the interfacial structural, mechanical and electronic properties of the contact between zinc oxide and graphene.

In this paper, we constructed six different interface configurations of Z-G, and theoretically investigated the interfacial properties of Z-G using first principles calculations based on density functional theory (DFT), the interfacial properties are as follows: interface binding energies, interfacial structural, mechanical and electronic properties etc. The interface distance of Z-G was separated rigidly ranging from 1 Å to 5 Å and each variable is 0.1 Å. The most stable interface configuration was found by interface binding energy and highest occupied molecular orbital-lowest unoccupied molecular orbital(HOMO-LUMO) gap, the Z-G interactions are obtained according to charge transfer and partial density of states (PDOS).

Section snippets

Model

Due to the hexagonal wurtzite ZnO is the most stable structure at room temperature and atmospheric pressure, and there are oxygen polar surface (0001¯) and zinc polar surface(0001) along c-axis preferred orientation [[22], [23], [24], [25]], so the interfacial contact of oxygen-graphene(OG) and zinc-graphene(ZG) are considered, and the ZnO-graphene interfacial configuration composed of supercell ZnO 3 × 3 × 2 and supercell graphene 4 × 4 × 1 are constructed respectively. Fig. 1 and Fig. 2 show

Interface binding energy

In order to calculate the interfacial binding energy of ZnO-graphene configuration, the interface binding energy is defined asEb=EZnOgrapheneEZnOEgraphenewhere EZnOgraphene, EZnO and Egraphene are the total energy of the ZnO-graphene configuration, ZnO substrate and monolayer graphene, respectively.

Consider that the potential functions of two interatomic interaction can be described by the Lennard-Jones potential [31,32], and the potential function parameters of Csingle bondZn [33] and Csingle bondO [34] also

Conclusions

The interface structure and properties of ZnO-graphene were studied using density functional theory. Three types of interfacial configurations (Znsingle bondC, Osingle bondC, Hsingle bondC) of both OG and ZG were built respectively to represent the contact between ZnO and graphene. The interface binding energies, interface structure and electronic properties all demonstrated that the contact between ZnO and graphene held together by van der Waals forces. Moreover, the interface binding energies showed the HC structure of OG is

Author information

Ping Yang is currently a professor in Jiangsu University in China, also is currently an editorial Member of Microsystem Technologies, an editorial Member of International Journal of Materials and Product Technology, Associate Editor in Chief of International Journal of Materials and Structural Integrity,a Member of IEEE, a director of China Precision Machine Society and a senior member of Chinese Institute of Electronics. He received his Ph.D in mechanical engineering from Huazhong University

Acknowledgements

This work was supported by the National Natural Science of Foundation of China under Grant 51575246 and 61076098, the support of Six talent peaks project in Jiangsu Province(JXQC_006), the support of A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions, the support of Postgraduate Research & Practice Innovation Program of Jiangsu Province(KYCX17_1761), during the course of this work.

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