Volume 113, Issue 7, 21 February 2013
Index of content:
113(2013); http://dx.doi.org/10.1063/1.4792032View Description Hide Description
Understanding charge carrier transport mechanisms in graphene fabricated by chemical vapor deposition (CVD) is important for electronic and thermal applications. We report results of structural, low temperature resistivity, and thermopower measurements in approximately four atomic layer thick centimeter size graphene. A semiconducting temperature dependence of the resistivity and a metallic temperature dependence of the thermopower in the same samples have been observed. The obtained results imply that intergranular charge carrier scattering in CVD graphene plays a major role in the electrical transport and a minor role in the thermal transport.
113(2013); http://dx.doi.org/10.1063/1.4792485View Description Hide Description
Whether or not nanoscale HfO2 has ferromagnetism is a debatable issue. In this study, monoclinic HfO2 nanorods with an average size of about 33.7 ± 3.1 nm in length and 8.9 ± 0.7 nm in width were synthesized via a chemical solution method. In comparison with many HfO2 nanoparticles/nanoclusters synthesized by physical methods, the as-prepared HfO2 nanorods were characterized by their better crystallinity and anisotropic shape. Interestingly, although the pristine HfO2 nanorods showed overall paramagnetic characteristics, when the nanorods were annealed in reducing environment, they exhibited clear room-temperature ferromagnetism (RTFM). The observed RTFM probably resulted from oxygen vacancies generated in the annealing process. In the mean time, it is suggested that factors such as the dimension, specific shape, and crystallinity of the HfO2 materials also should not be ignored when correlating the occurrence of ferromagnetism with defects.