For SEM, Al nanorods are imaged using a FEI Quanta 250 Field Emission Scanning Electron Microscope (FEI, Hillsboro, OR, USA). TEM is performed with Al nanorods that are grown directly onto carbon-coated TEM grids or with Al nanorods drop-coated onto Formvar TEM grids using a FEI Technai operating at 120 KeV. Thermal annealing experiments are performed in air using a resistance heated tube furnace. The annealing temperature is reached before the samples are placed inside the furnace on an alumina crucible. Timing begins when the sample is placed into the furnace and ends when the sample is removed. TEM samples are annealed while attached to

the substrate and are subsequently removed via sonication and drop-coated onto TEM grids. Results and discussion As the first set of experimental results,

Figure  2 contrasts the diameters of Al nanorods grown at different vacuum levels. The only difference in Daporinad order deposition conditions between Figure  2a and Figure  KU-60019 research buy 2b is the vacuum level. All other deposition conditions are the same; the substrate temperature is maintained at 300 K, the nominal deposition rate is 1.0 nm/s, and the incidence angle is 86°. Indeed, as we proposed, the lower vacuum leads to a smaller diameter of nanorods, with an average of ~125 nm; the higher vacuum leads to a larger diameter of nanorods – some areas as large as 500 nm. This set of results experimentally demonstrates the feasibility of the mechanism proposed in Figure  1. We recognize that the nitrogen (N) concentration is also high during growth. However, N loses to O in the reaction with Al. Later on, we will also

show that indeed, O is present and N is absent in the nanorods, using X-ray energy dispersive spectroscopy (EDS). Figure 2 Dependence of nanorod diameter on vacuum level. SEM images of Al nanorods grown at (a) a low vacuum of 10-2 Pa and (b) a high vacuum of 10-5 Pa; all at a substrate temperature of 300 K. Motivated by the technological demand for increased specific surface area and nanorods of the smallest diameter [7] and taking the demonstration of controllable growth one step further, we expect that a lower substrate temperature will further decrease the diameter of the nanorods by decreasing the diffusion of adatoms selleck monoclonal humanized antibody inhibitor from the tops of nanorods even more than with O alone. As shown in Figure  3 the diameter of Al nanorods is reduced to about 50 nm, which is an order of magnitude smaller than that in Figure  2b. In this case, we note that bunching, or bundling, occurs due to the uncontrolled separation of nanorods [11]; in contrast, the nanorods in Figure  2 are well separated. With the focus on the characteristic diameter, the nanorods that remain separate, or have branched out close to the substrate, are about 50 nm in diameter. We also note that a second cold finger is present in the chamber at a lower temperature than the substrate to mitigate the impingement and condensation of water vapor onto the substrate. Figure 3 Low-temperature growth.