Preparation of vertically aligned GaN@Ga2O3 core-shell heterostructured nanowire arrays and their photocatalytic activity for degradation of Rhodamine B

doi:10.1016/j.spmi.2020.106556

Superlattices and Microstructures

Volume 143, July 2020, 106556

https://doi.org/10.1016/j.spmi.2020.106556 Get rights and content

Highlights

•
Vertically aligned GaN@Ga₂O₃ NAs have been obtained by thermally oxidizing GaN NAs.
•
The Ga₂O₃ shell thickness can be controlled by oxidizing temperature and time.
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The core-shell NAs showed the best photodegradation efficiency of Rhodamine B.

Abstract

In this paper, vertically aligned GaN@Ga₂O₃ core-shell heterostructured nanowire arrays have been fabricated by thermal oxidation of GaN nanowire arrays. GaN nanowire arrays have been prepared by inductively coupled plasma etching. The GaN@Ga₂O₃ nanowire arrays have the good morphology and the thickness of the Ga₂O₃ shell can be controlled by the oxidation duration and temperature. The photocatalytic activity of vertically aligned GaN@Ga₂O₃ nanowires has been first evaluated by the degradation of Rhodamine B solution. Compared with the original GaN nanowires and the oxidized Ga₂O₃ nanowires, GaN@Ga₂O₃ nanowires exhibit superior photocatalytic activity. This finding suggests that GaN nanowire arrays with enhanced photocatalytic activity could be obtained by construct heterostructured GaN-based nanocomposite, which provides a new possibility for photocatalytic applications.

Graphical abstract

Vertically aligned GaN@Ga₂O₃ NAs have been fabricated by thermally oxidizing GaN NAs and the core-shell NAs exhibited enhanced photodegradation rate of Rhodamine B.

Introduction

Semiconductor nanomaterials have a wide range of applications due to their one-dimension structure, large surface-to-volume ratio and light-trapping ability [[1], [2], [3], [4], [5]]. Among numerous nanomaterials, GaN (E_g = 3.4 eV) and Ga₂O₃ (E_g = 4.8–4.9 eV) have attracted tremendous attention because of their wide bandgap, good chemical and thermal stability, and favorable optical and electric properties [[6], [7], [8], [9], [10]]. Recently, extensive efforts have been made on GaN-Ga₂O₃ nanocomposite materials because the unique heterostructure provides a variety of novel functions not originally available in either GaN or Ga₂O₃ nanostructures [[11], [12], [13], [14], [15], [16], [17], [18]]. GaN@Ga₂O₃ core-shell nanowires (NWs) are a case in point.

On the other hand, both GaN and Ga₂O₃ are promising photocatalytic materials due to their excellent chemical stability and being capable to photo-oxidative destruction of organic dyeing pollutants [[19], [20], [21], [22]]. Similar with other semiconductor nanocomposites, GaN@Ga₂O₃ core-shell nanocomposites are expected to improve photocatalytic activity [[23], [24], [25], [26]]. However, there are few reports of GaN@Ga₂O₃ core-shell nanocomposites to enhance photocatalytic efficiency [11]. In addition, photocatalytic applications of the vertically aligned GaN@Ga₂O₃ core-shell nanowire arrays (NAs) has not been reported so far.

For the preparation of GaN@Ga₂O₃ NWs, current researches have employed two main methods. i) Synthesis of the GaN@Ga₂O₃ core-shell NWs by hetero-epitaxy [12,13]. ii) Introduction of the Ga₂O₃ outer shell via thermal oxidation of the GaN core [[16], [17], [18]]. Among them, thermal oxidation is a preferable method with simple operation and low cost. However, most reported GaN@Ga₂O₃ core-shell nanowires are inclined or planar. As widely known, the inductively coupled plasma (ICP) etching is a simple and feasible approach to fabricate vertically aligned GaN NAs [[27], [28], [29]]. In this paper, we have prepared the vertically aligned GaN@Ga₂O₃ core-shell heterostructured NAs by thermally oxidizing GaN NAs fabricated via ICP etching.

The microstructure feature and the photocatalytic property for degrading Rhodamine B (RhB, C₂₈H₃₁N₂O₃Cl) of the GaN@Ga₂O₃ core-shell NAs have been first investigated. And the possible mechanism of the enhanced catalysis of GaN@Ga₂O₃ core-shell NAs for the photodegradation of RhB has been discussed.

Section snippets

Experimental details

The well-aligned GaN NAs were first fabricated by ICP etching using self-organized nickel nano-mask as the etching masks on GaN/sapphire (the experimental details were described in Ref. [28]). Then the GaN@Ga₂O₃ and Ga₂O₃ NAs were formed from the GaN NAs by controlling the thermal oxidation parameters. The oxidation process was carried out in an O₂ flow of 200 sccm at 850 °C for 15 min and at 1000 °C for 10 min, respectively. The microstructural features of the oxidized NAs were characterized

Material characterization

Fig. 1a shows the schematic diagram for the fabrication of vertically aligned GaN@Ga₂O₃ core-shell heterostructured NAs. Fig. 1b and c show the tilted-view and cross-sectional (the insets) SEM images of the original GaN NAs and the oxidized GaN@Ga₂O₃ NAs at 850 °C. Both the samples exhibit a morphology of vertically aligned nanowires with a density of 6.4 × 10⁸/cm². The average diameter and length of the original GaN NAs are ~0.21 μm and ~2 μm, respectively (Fig. 1b). After the oxidation, the

Conclusions

In conclusion, we have fabricated vertically aligned GaN@Ga₂O₃ core-shell heterostructured NAs by thermal oxidizing GaN NAs prepared by ICP etching. SEM and TEM observations verify that the prepared GaN@Ga₂O₃ nanowire owns uniform core-shell structure. The well-ordered core-shell NAs with controllable shell thickness have been demonstrated. Compared with pure GaN and Ga₂O₃ NAs, GaN@Ga₂O₃ NAs shows the better photocatalytic activity for the degradation of Rhodamine B. These results indicate that

CRediT authorship contribution statement

Liying Zhang: Conceptualization, Investigation, Writing - original draft. Yuewen Li: Resources, Validation. Xiangqian Xiu: Conceptualization, Supervision, Funding acquisition, Writing - review & editing. Guoqing Xin: Resources, Validation. Zili Xie: Resources, Validation. Tao Tao: Resources, Validation. Bin Liu: Resources, Validation. Peng Chen: Resources, Validation. Rong Zhang: Supervision, Funding acquisition. Youdou Zheng: Supervision, Funding acquisition.

Declaration of competing interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work is financially supported by the National Key R&D Program of China (2017YFB0404201), the State Key R&D Program of Jiangsu Province (BE2019103), the Six-Talent Peaks Project of Jiangsu Province (XCL-107), the Fund from the Solid-state Lighting and Energy-saving Electronics Collaborative Innovation Center, PAPD, and the Fund from the State Grid Shandong Electric Power Company.

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Preparation of vertically aligned GaN@Ga2O3 core-shell heterostructured nanowire arrays and their photocatalytic activity for degradation of Rhodamine B

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Experimental details

Material characterization

Conclusions

CRediT authorship contribution statement

Declaration of competing interests

Acknowledgements

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