Micro-PL was used to characterize the optical properties of the LOHN. Results and discussion Figure 1a shows a typical SEM image of the GaN nanowires grown on the substrate using Ni as a catalyst. Ni is a well-known catalyst for the growth of GaN nanowires [24]. However, the nanowires grow randomly on the substrate. buy OSI-027 In fact, the vertical growth of GaN nanowires has rarely been achieved using a Ni catalyst. Figure 1 SEM images of GaN nanowires grown by the vapor–liquid-solid mechanism. (a) SEM images of GaN nanowires grown by Ni BTSA1 supplier catalysts. (b) SEM images

of GaN nanowires grown by Au/Ni catalysts. (c) Cross-sectional SEM images of GaN nanowires grown by Ni catalysts. Inset of (c) shows the end of the nanowires. (d) Cross-sectional SEM images of GaN nanowires grown by Au/Ni catalysts. Inset of (d) shows the end of the nanowires. (e) Schematic illustration of the VLS process for GaN nanowire grown by Ni catalysts. (f) Schematic illustration of the VLS process for GaN nanowire grown by Au/Ni catalysts. Figure 1c is the SEM image of the nanowire-substrate interface. It can be seen that the substrate is covered by an interfacial layer on which GaN nanowires grow randomly. The inset of Figure 1c shows the end of the nanowires. A metal

globule can be observed at the end, which clearly indicates that the nanowires are grown by the VLS mechanism. The diameter and length of nanowires are 80 to 100 nm https://www.selleckchem.com/products/cilengitide-emd-121974-nsc-707544.html and several hundred micrometers, respectively. Because the nanowires grow on the interfacial layer, the interfacial layer is grown prior to the nanowires, though the catalyst for aminophylline the nanowires is coated on the substrate. This means that the VS mechanism of direct deposition of GaN from the vapor for the growth of the interfacial layer works at the early stage, prior to the working of the

VLS mechanism. Previous reports have shown that the initial GaN grows on the interfacial layer after the GaN nanowires are grown using Ni catalyst [23]. It was found that the catalyst does not work in the early stage, in which the interfacial layer instead grows on the substrate due to a VS mechanism. After the catalyst works, the GaN nanowires grow on the interfacial layer due to a VLS mechanism. The Ni catalyst, leading to the VLS process of nanowires in the second step is reassembled from the metal films onto the surface of the interfacial layers [23]. Therefore, the growth of the interfacial layer is expected to be faster than that of the nanowires in the case of the Ni catalyst. This may result from the complexity of the VLS mechanism. The VLS mechanism involves three phases and two interfaces (specifically, vapor–liquid and liquid–solid interfaces). The chemical reactions of dissolution and precipitation are involved in the working of the VLS mechanism, which is not the case with the VS mechanism [25]–[27]. Diffusion in the gas and liquid phases is also involved.