Showing papers by "Gyu Tae Kim published in 2001"

Growth and electrical transport of germanium nanowires

Abstract: Single crystalline germanium nanowires have been synthesized from gold nanoparticles based on a vapor–liquid–solid growth mechanism. Germanium powder was evaporated at 950 °C, and deposited onto gold nanoparticles at 500 °C using argon as a carrier gas. The diameter of the germanium nanowires ranged from 20 to 180 nm when gold thin films were utilized as the substrate, while the nanowires grown from 10 nm Au particles showed a narrower diameter distribution centered at 28 nm. The growth direction of germanium nanowires is along the [111] direction, determined by high resolution transmission electron microscopy. Transport measurements on individual Ge nanowires indicate that the wires are heavily doped during growth and that transport data can be explained by the thermal fluctuation tunneling conduction model.

Temperature-induced change from p to n conduction in metallofullerene nanotube peapods

Abstract: Metallofullerene nanotube peapods were prepared by introducing Dy@C82 into the interior space of single-walled carbon nanotubes. Transport measurements show that the Dy@C82 molecules function as electron donors and transfer charge to the carbon nanotube host. The amount of charge transferred varies with the temperature. At room temperature, the doped nanotube shows p-type behavior as seen from the response to a back gate. As the temperature decreases, the conductance becomes n type and at T<215 K metallic behavior is observed, indicating the degenerate state by doping. Below about 75 K, single-electron charging phenomena dominate the transport and show irregular Coulomb blockade oscillation, implying that the insertion of Dy@C82 splits the tube into a series of several quantum dots.

Simple efficient coordinate markers for investigating synthetic nanofibers

Abstract: A system of simple coordinate markers has been developed to facilitate the identification of individual synthetic nanofibers adsorbed on a substrate The markers are deposited by electron beam lithography and allow to locate any spot on an atomic force microscope image and to deposit new structures close to this spot, such as lithographic contacts to nanotubes As a demonstration, current–voltage characteristics of a junction between a metallic carbon nanotube and an n-type V2O5 nanofiber were recorded

Soft Reverse Current-Voltage Characteristics in V2O5 Nanofiber Junctions

Abstract: : V2O5 nanofibers showed the rectifying current-voltage characteristics under an asymmetric contact configuration at room temperature, indicating the formation of a Schottky diode. The ideality factors as a Schottky diode were estimated to be 6.1 at the forward bias and 1.4 at the reverse bias. The larger current at the reverse bias defined by the negative voltage at the metal electrode may originate from the contribution of the tunneling via field emission or thermionic field emission. The ultimate geometric size of nanofibers enhances the influence of the tunneling mechanism and modifies the nano-scale Schottky diode, requiring more understanding in designing the nano-scale electronic devices with the metal contacts.

Role of the metal in contacting Single-Walled Carbon Nanotubes

Abstract: Electrodes have been defined by e-beam lithography on top of Carbon Nanotubes in order to reduce the contact resistance between metal and Nanotube. Individual Single-Walled Carbon Nanotubes or individual thin bundles were contacted with different metals (Au, AuPd, Al, and Co). The electrode material has been varied in order to investigate the Nanotube/metal-contact. The adhesion properties of the metals and the Carbon Nanotubes on the substrates turned out to be crucial.