Elsevier

Journal of Alloys and Compounds

Volume 613, 15 November 2014, Pages 37-41
Journal of Alloys and Compounds

Growth of ZnO nanorods on graphite substrate and its application for Schottky diode

https://doi.org/10.1016/j.jallcom.2014.05.110Get rights and content

Highlights

  • All solution process for growth of ZnO nanorods on graphite is investigated.

  • Characteristics of the ZnO nanorods on graphite were compared that on silicon substrate.

  • ZnO nanorods/graphite showed Schottky diode behavior with asymmetric photoresponse.

Abstract

We report on the growth of ZnO nanorods (NRs) grown on graphite and silicon substrates via an all-solution process and also studied the characteristics of their heterojunctions. Structural investigations indicated that morphological and crystalline properties were not significantly different for the ZnO NRs on both substrates. However, optical properties from photoluminescence spectra showed that the ZnO NRs on graphite substrate contained more point defects than that on Si substrate. The ZnO NRs on both substrates showed typical rectification properties exhibiting successful diode formation. The heterojunction between the ZnO NRs and the graphite substrate showed a Schottky diode characteristic and photoresponse under ultraviolet illumination at a small reverse bias of −0.1 V. The results showed that the graphite substrate could be a good candidate for a Schottky contact electrode as well as a conducting substrate for electronic and optoelectronic applications of ZnO NRs.

Introduction

ZnO nanorods (NRs) have received much attention due to their direct wide band gap of 3.37 eV, high exciton binding energy of 60 meV, and large piezoelectric coefficient [1], [2]. In particular, a preferred directional growth along the c-direction of the wurtzite crystal structure enables the ZnO crystals to be a promising constituent of various novel device applications, such as transistors, sensors, and piezoelectric, thermoelectric, electrochemical and optoelectronic devices [1], [2]. The fabrication of ZnO NRs has been demonstrated on a variety of substrates including metals, semiconductors, insulators, and polymers [1], [2], [3], [4]. Recently, accompanying with active research on the heterostructures between graphene and semiconductors [5], [6], graphite also has received much attention as a potential substrate for the growth of semiconductors owing to its excellent mechanical and chemical stability, and high thermal and electrical conductivity [7]. Furthermore, graphite has a potential advantage for transferable substrate since it consists of a multi-layer system with nearly decoupled two dimensional (2-D) graphene planes [8]. There are some reports about the deposition of ZnO nanostructures on graphite substrate by the vapor phase method [9], electrochemical deposition [10], and hydrothermal growth combined with the thin film deposition method [11]. However, there are only a few investigations reporting the growth of ZnO NRs on graphite substrate by the all-solution-process method, especially using the hydrothermal method, even though this method has many advantages including a low temperature process which make it applicable to the integration and in situ fabrication of various devices [12], [13]. For a compatible application of ZnO NRs to other devices, all-solution process method at a low temperature on graphite substrate should be possible, and its performance could be compared with conventional substrate, silicon (Si). In this paper, we report on the growth of ZnO NRs on graphite substrate, and on comparative study of the growth of ZnO NRs on Si substrate by using the all-solution process two-step hydrothermal method.

Section snippets

Experimental

The ZnO NRs were grown on highly-oriented pyrolytic graphite and p-type Si (1 0 0) substrates using an all-solution process two-step hydrothermal method involving the formation of a ZnO seed and main ZnO NR layers. Prior to growth, the substrates were rinsed sequentially in acetone, ethanol, and deionized (DI) water to remove contamination. A seed layer for the ZnO NRs was formed by dipping both substrates into 40 mM zinc acetate dihydrate [Zn(CH3COO)2⋅2H2O] dissolved in ethanol solution, followed

Results and discussion

Fig. 1 shows FE-SEM images of the ZnO NRs grown on the p-type Si (1 0 0) and graphite substrates. Without the seed layer, no deposit was observed on both substrates, even for a longer growth time. This indicates that the seed layer plays a critical role in the growth of ZnO NRs on the substrates. The diameter of the ZnO NRs on Si and graphite substrates are 70 nm and 50 nm, respectively. The diameter of the ZnO NRs grown on graphite substrate was slightly smaller than those on Si substrate. And the

Conclusion

In conclusion, we compared the properties of ZnO NRs on graphite and Si substrates grown by using a two-step hydrothermal method. Structural investigations using FE-SEM and XRD showed no significant differences in the morphologies and crystalline quality. Optical investigations using PL measurements showed that the ZnO NRs on graphite contained more lattice point defects than on Si substrate. The IV characteristics for both samples showed typical rectification properties, exhibiting successful

Acknowledgements

The authors thank Mr. Jae-Min Park (Yeungnam University) for assistance with the experiments. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (2012R1A1A1001711) and by DGIST (13-EN-03).

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