Growth of MgO nanowires assisted by the annealing treatment of Au-coated substrates
Introduction
Since the discovery of carbon nanotubes (CNTs), much technological and scientific excitement has been raised by the discovery of various forms of nanostructures [1], [2], [3], [4]. Among them, one-dimensional (1D) structures including nanowires, nanobelts and nanowires are supposed to have potential applications to nanoelectronics and optoelectronics, owing to their novel physical properties. Magnesium oxide (MgO) is a typical wide-band-gap insulator, having found many applications as catalysis, additives in refractory, paint and superconductor products, and as substrates for thin film growth [5], [6]. Accordingly, many research groups have reported on the synthesis of 1D MgO nanostructures [7], [8], [9], [10], [11], [12], [13], however, they generally studied from the viewpoint of the preparation method and characterization.
The CNT growth is known to depend strongly on the characteristics of metal catalyst, although the complete mechanism has not been determined. Therefore, we need to investigate the effect of the substrate material on the growth behavior of MgO nanostructures.
In the present communication, we applied thermal annealing treatment to the Au-coated substrates before we grow the MgO structures by a thermal evaporation of MgB2 powders. Obtaining the MgO nanowires by controlling the predeposition annealing temperature, we have investigated the structural and photoluminescence (PL) properties of the as-prepared MgO nanowires.
Section snippets
Experimental
We employed Au-coated Si substrates. In order to fabricate the Au-coated Si substrates, we used Si as the starting material onto which a Au layer of about 3 nm thick was deposited by ion sputtering (Emitech, K757X). Since our objective was to investigate the effect of Au-coated substrate with respect to its morphology, we have preformed the thermal annealing treatment prior to MgO deposition, in which temperatures were in the range of 300–700 °C for 0.5 h in a flow of nitrogen (N2) gas (flow rate;
Results and discussion
Fig. 1a–c shows the SEM images of the Au (3 nm-thick)-coated substrates prior to MgO deposition with the annealing temperature of 300, 500, and 700 °C, respectively. From the SEM images of the sample with the predeposition annealing at a temperature of 700 °C, we observe the relatively wide island-like structures, while we observe the relatively narrow particle-like structures in the pre-annealed samples in the range of 300–500 °C. We reveal that not only the width of Au structures but also the
Conclusion
We have successfully fabricated MgO nanowires via a thermal evaporation method of heating MgB2 powders. SEM images reveal that the formation of Au islands on substrates, by carrying out the predeposition annealing on Au-coated Si substrate, plays a crucial role in subsequently growing the MgO nanowires. XRD, HRTEM and SAED analyses coincidentally indicate that the nanowire is crystalline. The PL measurement with the Gaussian fitting shows apparent visible light emission bands centered at 438 nm
Acknowledgement
This work was supported by Inha University Research Grant.
References (21)
- et al.
Chem. Phys. Lett.
(2003) - et al.
Chem. Phys. Lett.
(2001) - et al.
Chem. Phys. Lett.
(2002) - et al.
Chem. Phys. Lett.
(2003) - et al.
Chem. Phys. Lett.
(2006) - et al.
Mater. Res. Bull.
(2005) - et al.
Chem. Phys. Lett.
(2002) Nature
(1991)- et al.
Science
(1995) - et al.
Acc. Chem. Res.
(1999)