With the use of O as a surfactant, the Al nanorods are likely covered with a layer of Al oxide, which may protect the nanorod morphology from degradation at high temperatures. As the inset of Figure  4a shows, annealing the Al nanorods, which are deposited at room temperature under low vacuum,

in air at 475 K for 1 day leads to no visible change in morphology (in comparison to the image in Figure  2a). Our annealing of the same Al nanorods in air at room temperature for 30 days leads to no visible change of morphology, either. The EDS spectra confirm that the nanorods contain Al and O atoms, but no N or other atoms that exist in air or low vacuum. This EDS analysis acts as further evidence to support learn more that O is indeed the dominating chemical element. The accompanying TEM image shows a crystalline core and an amorphous shell of ~2 nm in thickness. Here, the samples are taken immediately from the fabrication chamber to the Staurosporine price microscope while under vacuum to prevent oxide formation. Electron diffraction, not shown here, confirms that the core is crystalline aluminum

and the shell is amorphous aluminum oxide. Further, TEM images show that the core and shell thicknesses do not change through annealing at 475 K, indicating that the crystalline or amorphous structures remain unchanged (Figure  4b). Pushing the limit of annealing temperature to 875 K (and in air for 30 min), our SEM images do not reveal any visible changes in morphology, but the TEM image in Figure  3b does reveal a marked increase in oxide shell thickness and loss of crystalline core. In passing, we note that annealing at 1,475 K in air for 30 min results in the total conversion of the nanorod into Al2O3. Figure 4 Analysis of annealed Al nanorods. (a) EDS spectra of Al nanorods as grown and after annealing at 475 K for 1 day in air, with the SEM image of the annealed Al nanorods as an inset and (b) TEM images of Al nanorods before (left) and after the annealing at 475 K (middle) and 875 K (right). In passing, we remark on the impact of the oxide shell. To realize the structures

in previous literature studies [6, 10], surface oxide formation is necessary. Even with this oxide layer, Al nanorods from PVD perform well in technological applications [6, 10]. A level of control of Al nanorod diameter is find protocol possible mTOR inhibitor through only substrate temperature control, for the growth of ultra-pure Al nanorods without an oxide shell, but at the expense of extremely low substrate temperatures. Conclusions To summarize, we propose and experimentally demonstrate a mechanism of the controllable growth of Al nanorods using PVD, for the first time, through the use of O as a surfactant. Based on this mechanism, we have achieved the control of Al nanorod diameter from ~50 to 500 nm by varying the amount of O, the vacuum level, and the substrate temperature. The Al nanorods are thermally stable.