Lunhui Guan

Two-bit memory devices based on single-wall carbon nanotubes: demonstration and mechanism

Two-bit memory devices of SWNTs, based on the hysteresis effect, have been demonstrated for the first time. The pertinent memory behaviours seem to originate from the capacitive effect due to polarization of molecules, especially the surface-bound water molecules on SiO2 in close proximity to carbon nanotubes. Our investigations are intimately linked with ultrahigh-density memory applications, and possibly go a long way in broadening the memory applications of SWNTs, for example from nonvolatile to volatile cells.

Super-long continuous Ni nanowires encapsulated in carbon nanotubes

Super-long continuous Ni-filled carbon nanotubes were synthesized by the chemical vapor deposition (CVD) method with cloth-like single-walled carbon nanotube (SWNT) raw soot produced by the arc-discharge method as catalyst; the Ni nanowires inside the carbon nanotubes are single crystals, with an average diameter of 40 nm and up to tens of micrometres in length.

STRUCTURAL AND ELECTRONIC PROPERTIES OF ONE DIMENSIONAL KxC60 CRYSTAL ENCAPSULATED IN CARBON NANOTUBE

The structural and electronic properties of potential one dimensional (1D) superconductor — KxC60 chain encapsulated inside a single-walled carbon nanotube is studied using first principles calculations. The stoichiometry of K to C60 of the 1D KxC60 crystal can reach 9, in contrast to a maximal stoichiometry of 6 found in the K doped bulk fullerides. The K 4s electrons are completely ionized, and fill chiefly the C60-derived bands in a nonrigid way. The density of states at the Fermi level of the encapsulated 1D KxC60 crystal is comparable to that in K doped bulk fullerides.

Field-effect transistors based on single-wall carbon nanotubes bundles

The electric transport properties of single-walled carbon nanotubes (SWNT) bundles array have been measured. We report the fabrications and performances of nanoscale field-effect transistors (FET) based on SWNT bundles array. In addition to p-type FET, we present a new technique by which ambipolar FETs can be fabricated. The I/sub on// I/sub off/ ratio of ambipolar FETs approaches 5 orders of magnitude. The reasons for ambipolar character are also qualitatively discussed. Both p-type and ambipolar FETs exhibit hysteresis in their electrical characteristics.

Gate-controlled rectifying behavior in C 70 @SWNTs networks

We observed gate-controlled current rectification in C 70 @SWNTs networks. The electrical transport characterization can be fitted well with the conventional Schottky diode model. The origin of the rectifying behavior in peapod networks device is also qualitatively discussed. This paper also demonstrates a strategy for diode fabrication based on peapod networks and selective electrical breakdown procedure.

Ambipolar field-effect transistors based on fullerene peapods

The electrical transport properties of C/sub 70/ and C/sub 60/ fullerene peapods are investigated. We report the fabrications and performances of field-effect transistors (FETs) based on C/sub 70/ and C/sub 60/ fullerene peapods. Most of the fullerene peapod-FETs exhibit ambipolar characteristics at room temperature in air. The origin of ambipolar behavior is also qualitatively discussed. The ambipolar FETs based on fullerene peapods exhibit hysteresis effect in their electrical characteristics.