Pavel S. Dorozhkin

Semiconducting B–C–N nanotubes with few layers

Perfectly ordered nanotubes (NTs) displaying a limited number of defect-free B-C-N shells (typically 2-4) were synthesized from CVD C NTs and a mixture of boron oxide and gold oxide placed in a flowing N2 atmosphere at ∼1950 K. The NTs were analyzed using field emission conventional and energy-filtered (Omega filter) high-resolution electron microscopes, and electron energy loss and energy dispersive X-ray spectrometers. NTs with inner diameters of 0.9-4.0 nm were frequently assembled in bundles consisting of several tubes and extending up to 1-2 μm in length. Two-terminal transport measurements on individual B-C-N nanotube bundles were carried out in-situ in a Fresnel projection microscope. The bundles displayed semiconducting behavior with an estimated band gap of ∼1 eV.

Field emission from individual B–C–N nanotube rope

The field-emission characteristics of individual ropes made of B–C–N nanotubes were measured in situ in a low-energy electron point source microscope. The tungsten field emission tip of the microscope was used as a movable electrode, approaching the rope, and acting as an anode during field-emission measurements. The atomic structure and chemical composition of the ropes were analyzed by high-resolution transmission electron microscopy and electron energy-loss spectroscopy. The tubes assembled within the ropes typically revealed open-tip ends, a small number of layers and zigzag chirality. We found that the field-emission properties of the B–C–N nanotube ropes are competitive with conventional C nanotubes, with the expected additional benefit that the B–C–N ropes exhibit higher environmental stability.

Cables of BN-insulated B–C–N nanotubes

BN-covered and insulated multiwalled semiconducting B-C-N nanotubes (NT), assembled in long ropes were produced and electrically tested. The atomic structure and chemical composition of ropes were analyzed by high-resolution transmission and energy-filtered electron microscopy. Individual ropes displayed perfect insulating performance of BN-rich outer layers and excellent field emission.

Charge distribution mapping by low energy electrons

We demonstrate how low energy electron point source microscope can be used for quantitative mapping of linear charge distribution along one-dimensional wires. Imaging of electrically biased carbon nanotube ropes suspended across two electrodes showed different charge distributions for three different experimental situations: (1) ropes having good ohmic contacts to both electrodes, (2) ropes with one good and one poor ohmic contacts, and (3) ropes with one end contacted and the other end free standing. The technique gives a linear charge density resolution below 0.1e per nanometer with a spatial resolution better than 10nm. The resolution can be further improved by the proper modification of experimental setup.

Synthesis, Analysis, Transport and Field emission Measurements of Compound B-C-N Nanotubes

Multiwalled B-C-N nanotubes of various morphologies and chemical compositions were synthesized by reacting C-based nanotube templates with boron oxide and nitrogen at 1573 K-2173 K. The nanotubes were thoroughly analysed using a high-resolution field-emission 300 kV transmission electron microscope (TEM), an energy-filtered field-emission 300 kV electron microscope (Omega filter), an electron energy loss spectrometer and an energy dispersion X-ray detector. Transport and field emission properties of the nanotubes were studied using a low energy electron point source microscope and via in-situ measurements in TEM equipped with a scanning tunnelling microscope (STM) unit.

Synthesis, structural and chemical analysis, and electrical property measurements of compound nanotubes in the B‐C‐N system

Homogeneous or heterogeneous multi‐walled nanotubes composed of B, C and N atoms were prepared through high‐temperature chemical reactions (1700–2000 K) between C (or CNx) nanotubes, boron oxide and nitrogen. Morphology, helicity, chemical composition and atomic species distribution in nanotubes were studied using field emission 300 kV transmission electron microscopes (TEM) JEOL‐3000F equipped with a Gatan 766 Electron energy loss detector and JEOL‐3100FEF equipped with an Omega Filter. Transport and field emission properties of nanotubes were studied using a low energy electron point source microscope.