The electric transport properties of an individual vertical multiwall carbon nanotube (MWCNT) were studied in situ at room temperature in a scanning electron microscope chamber. It was found that the single MWCNT has a large current-carrying capacity, and the maximum current can reach 7.27 mA. At the same time, a very low resistance of about 34.4 ohms and a high conductance of about (460-490)G0 were obtained. The experimental observations imply a multichannel quasiballistic conducting behavior occurring in the MWCNTs with large diameter, which can be attributed to the participation of multiple walls in electrical transport and the large diameter of the MWCNTs.

A uniform diamond nanocone array was formed by plasma etching of diamond film in a hot filament chemical vapor deposition (HFCVD) system. A surface amorphous carbon coating layer, which is formed during CH4/H2 plasma-etching process, was removed by Ar plasma in a reactive ion etching system. The hydrogenation of diamond nanocones was performed in H2 ambience by using the same HFCVD system. The air-diluted NH3 and NO2 gases sensing properties of the diamond cone arrays had been studied by using electric current versus measurement time characteristics at room temperature. The repeatable chemical sensing properties of the hydrogenated diamond cone array sensor are enhanced, in comparison with as-formed diamond film. Surface two-dimensional hole gas structure and greatly increased surface-to-volume ratio both play a key role for the excellent detection performance. As-formed diamond nanocone arrays show a promising prospect for applications as chemical sensor for both reducing (NH3) and oxidizing (NO2) gases.

The nanocrystalline diamond films with different morphologies and roughness were synthesized by a bias-assisted hot filament chemical vapor deposition method. It was found that the nanocrystalline diamond film exhibited low-k dielectric properties with the increase of CH4 concentration during diamond deposition. The low-k nanocrystalline diamond film with grain size of around 40nm and dielectric constant of 2.4 was obtained at the CH4 concentration of 16% and the bias of −140V. The low dielectric constant can be mainly attributed to the decrease of diamond grain sizes and the formation of more nanopores in as-grown nanocrystalline diamond film, both of which were discussed in details based on the grain size determined band gap expansion effect and the two-phase dielectric mixing model, respectively.