The other issue in the modulation of nanowires is the fabrication of heterostructure nanowires such as coaxial heterostructure nanowires (COHN) or longitudinal heterostructure

nanowires (LOHN) that can tune and maximize optoelectronic properties. For example, the luminescence from the GaN/InGaN COHN can be tuned for the entire visible light wavelength (1.12 to 3.34 eV) on the basis of the In composition in the InGaN shells [13]. The InGaN shell in the COHN is also helpful selleck in achieving efficient radiative recombination of injected carriers, while confining both carriers and photons in the nanowires. Nanowires are grown by means of a vapor–liquid-solid (VLS) mechanism [14]. This mechanism can be used to grow nanowires TGF-beta inhibitor clinical trial vertically by establishing an epitaxial relationship between the nanowires and substrates [15]–[21]. In the case of GaN nanowires, however,

vertical growth using the VLS mechanism has rarely been reported BI 2536 nmr [22]. This is because an interfacial layer is formed on the substrates by the vapor-solid (VS) mechanism prior to the growth of GaN nanowires by the VLS mechanism, thus preventing the establishment of an epitaxial relationship between nanowires and substrates [23]. It is thus difficult to grow vertically aligned GaN nanowires reliably using the current VLS mechanism. In this report, we present a method to grow GaN nanowires vertically via the VLS mechanism using Au/Ni bi-metal catalysts. We also demonstrate the fabrication of GaN/InGaN COHNs or LOHNs using these vertically grown GaN nanowires and the tunability of the optical properties of the nanowires. Methods GaN nanowires were grown by means of metal organic chemical vapor deposition using trimethylgallium (TMGa) and ammonia (NH3) as group III and V precursors, respectively. Nickel/gold thin films (0.5/2-nm thick) were deposited on the sapphire (c-Al203) substrate coated with a 3-nm-thick GaN film (c-plane). Homemade reactor,

consisted with furnace (Model Blue M, Lindberg Co., Ltd., Asheville, NC, USA) and quartz tube with diameter of 1 inch, was used for the growth of GaN nanowires. The substrates were loaded into a quartz reactor and heated to the growth temperature (800°C) for 25 min under the flow condition of 100 sccm H2 and 100 sccm N2. The GaN nanowire was grown at 800°C for Cobimetinib order 30 min by flowing 0.5 sccm of TMGa and 50 sccm of NH3 and then cooled down to room temperature. The GaN/InGaN COHNs were fabricated on a vertically grown GaN nanowire by further depositing the InGaN and GaN shell on the surface of the nanowire at 600°C to 750°C using TMGa, TMIn, and NH3. InGaN LOHNs were also fabricated on a vertically grown GaN nanowire by further supplying TMGa and TMIn and NH3 to the catalyst. The InGaN layer was grown at 550°C. The nanowires were characterized using scanning emission microscopy (SEM), transmission emission microscopy (TEM), and energy-dispersive spectroscopy (EDS).