RESUMO
A novel method for synthesis of high quality InN nanowires, at temperatures well above their decomposition temperature, has been demonstrated by utilizing controlled oxygen flow in the growth chamber. Detailed structural and chemical analyses indicate that the nanowires consist of pure InN, with no evidence of In2O3 detected by any of the characterization methods. It is proposed that the oxygen, pre-adsorbed on the Au catalyst surface, assists in accelerating the decomposition of NH3 at the growth temperature by providing high concentration of atomic nitrogen to assist in the growth, and prevent decomposition of the InN nanowires, without getting incorporated in them. The proposed role of oxygen is supported by improved material quality at higher oxygen flow rates.
RESUMO
We report a remarkable phenomenon that electron beam irradiation (EBI) significantly enhances the Young's modulus of zinc tin oxide (ZTO) nanowires (NWs), up to a 40% increase compared with the pristine NWs. In situ uniaxial buckling tests on individual NWs were conducted using a nanomanipulator inside a scanning electron microscope. We propose that EBI results in substantial atomic bond contraction in ZTO NWs, accounting for the observed mechanically stiffening. This argument is supported by our experimental results that EBI also reduces the electrical conductivity of ZTO NWs.
Assuntos
Nanotubos/química , Nanotubos/efeitos da radiação , Compostos de Estanho/química , Compostos de Estanho/efeitos da radiação , Óxido de Zinco/química , Óxido de Zinco/efeitos da radiação , Módulo de Elasticidade/efeitos da radiação , Elétrons , Dureza/efeitos da radiação , Teste de Materiais , Conformação Molecular/efeitos da radiação , Nanotubos/ultraestruturaRESUMO
Diameter-dependent electrical properties of InN nanowires (NWs) grown by chemical vapor deposition have been investigated. The NWs exhibited interesting properties of coplanar deflection at specific angles, either spontaneously, or when induced by other NWs or lithographically patterned barriers. InN NW-based back-gated field effect transistors (FETs) showed excellent gate control and drain current saturation behaviors. Both NW conductance and carrier mobility calculated from the FET characteristics were found to increase regularly with a decrease in NW diameter. The observed mobility and conductivity variations have been modeled by considering NW surface and core conduction paths.
RESUMO
We report the observation of remarkable electrical self-healing in mechanically damaged ZnO nanobelts. Nanoindentation into intrinsically defect-free ZnO nanobelts induces deformation and crack damage, causing a dramatic electrical signal decrease. Two self-healing regimes in the nanoindented ZnO nanobelts are revealed. The physical mechanism for the observed phenomena is analyzed in terms of the nanoindentation-induced dislocations, the short-range atomic diffusion in nanostructures, and the local heating of the dislocation zone in the electrical measurement.
RESUMO
We report on shot noise cross spectrum measurements in a beam splitter configuration. Electrons tunneling through potential barriers are incident on a beam splitter and scattered into two separate channels. Such a partition process introduces correlations between the fluctuations of the two currents. Our work has confirmed that the generally expected negative correlations resulted from sub-Poissonian electron sources. More interestingly, positive cross correlations associated with barriers exhibiting super-Poissonian shot noise have also been observed. We have found that both positive and negative correlations can be related to the noise properties of the electron source.
RESUMO
We report nonlocal spin injection and detection experiments on mesoscopic Co-Al2O3-Cu spin valves. We have observed a temperature-dependent asymmetry in the nonlocal resistance between parallel and antiparallel configurations of the magnetic injector and detector. This strongly supports the existence of a nonequilibrium resistance that depends on the relative orientation of the detector magnetization and the nonequilibrium magnetization in the normal metal providing evidence for increasing interface spin scattering with temperature.
RESUMO
We report measurements of conductance distribution in a set of quasi-one-dimensional gold wires. The distribution includes the second cumulant or the variance which describes the universal conductance fluctuations, and the third cumulant which denotes the leading deviation. We have observed an asymmetric contribution--or, a nonvanishing third cumulant--contrary to the expectation for quasi-one-dimensional systems in the noninteracting theories in the one-parameter scaling framework, which include the perturbative diagrammatic calculations and the random matrix theory.