Transition-metal doped zinc oxide nanowires.

The introduction of impurity atoms into semiconducting materials is the primary method for controlling the properties of the semiconductor, such as band gap or electrical conductivity. This practice is routinely performed with bulk semiconductors and, more recently, has been extended to nanoscale semiconductors as well. In particular, II–VI and III–V semiconductors that have been doped with transition metals are currently generating much research interest, principally for their novel magnetic properties. These semiconductors are commonly called dilute magnetic semiconductors and are envisioned to be potential building blocks for spintronic devices. One such material is transition-metal doped zinc oxide (Zn1 xMxO), which has been theoretically predicted to be ferromagnetic at room temperature. 2] Although this system has been under experimental study for some time, the vast majority of research conducted on this material has been done on bulk crystals or thin films. There are very few reports on the fabrication of one-dimensional nanostructures of Zn1 xMxO, and high-temperature, vapor-phase methods are employed in the syntheses. Although this approach has proven quite effective for the production of a multitude of nanoscale semiconductors, gas-phase syntheses are considerably limited in regards to homogeneous doping and alloying because of high-growth temperatures. Solution-based synthetic schemes possess inherent advantages in the above areas over vapor-phase routes, in addition to ecological benefits. Whereas there have been several reports on the synthesis of pure ZnO nanowires from the solution phase, the only solution-based methods for the production of Zn1 xMxO yield isotropic quantum dots, such as those reported by Gamelin et al. To date, no reports of anisotropic, transition-metal doped ZnO nanowires grown from the solution phase exist. We present herein the synthesis and characterization of cobalt-doped zinc oxide (Zn1 xCoxO) nanowires grown by a solution-phase synthesis. The synthetic process presented herein also allows for the doping of different transition metals (e.g., Mn, Fe, Cu); however, this report is limited to the cobalt-doped system. The nanowires were synthesized by the thermal decomposition of zinc acetate and cobalt(ii) acetate in refluxing trioctylamine (see the Experimental Section). Figure 1 shows