Jinlong Gong

Enhanced electron field emission of carbon nanotubes by Si ion beam irradiation

The electron field emission of carbon nanotubes (CNTs) has been enhanced by Si ion beam irradiation. The defects generated by ion beam irradiation and the absorbed molecules on the CNTs were responsible for the enhancement of electron field emission. This investigation provides a possible way to improve the electron field emission properties of CNTs and understand the mechanism of electron field emission enhancement of CNTs.

FORMATION OF LIMC60 + 2N (M = 1-3, N = -1 TO 4) ENDOHEDRAL FULLERENES IN THE COLLISION OF LI+ ION WITH C60

Abstract The collision-induced reaction of Li + with neutral C 60 vapor was investigated in the energy range of 10–100 eV using laser desorption time-of-flight mass spectrometry (TOFMS). From the positively charged TOF mass spectra, the maximum intensity of [Li@C 60 ] + was determined, which was about 60% of that for the C 60 + . In addition, [Li 2 @C 60 ] + complex was also observable. The negatively charged lithium endohedral fullerene ions of both fragment products (C 58 ) and adductive products were observed in the negatively charged TOF mass spectra for collision energies in the range of 30–50 eV. In addition, it was found that up to three lithium atoms can be trapped into the fullerene cages and the intensity of [Li m C 60+2 n ] − ( m =1,2 and 3, n =0,1,2,3,4) in the mass spectra decreases with the increase of m and n . Li + inserts into the C 60 cage via a “slip-through” mechanism was proposed.

DIAMOND NANORODS FROM CARBON NANOTUBES BY HYDROGEN PLASMA TREATMENT

Single crystalline diamond nanorods with diameters of 4–8 nm and with lengths up to 200 nm have been synthesized by hydrogen plasma post-treatment of multiwalled carbon nanotubes. The diamond nanorods were identified to have a core-sheath structure with inner core being diamond crystal and outer shell being amorphous carbon. A growth mechanism for the diamond nanorods was proposed.

Multi-walled carbon nanotubes under N ion beam irradiation

The multi-walled carbon nanotubes (MWCNTs) irradiated by N ion beams at different temperatures were investigated. At the irradiation dose of 1times1017 ions/cm2, the MWCNTs completely became amorphous at room temperature. The amorphous carbon of the N ion irradiated MWCNTs could be evaporated by 5 KeV focused electron beam irradiation. That is, the irradiated MWCNTs could be modified by the low energy electron beam irradiation. Nevertheless, with increasing the temperature, the radiation damage in MWCNTs that could destroy the structure was minimized. Moreover, at the temperature of 800 K, the interconnection of adjacent parallel MWCNTs could be realized at the irradiation dose of 1.5times1017 ions/cm2. This interconnection was ascribed to the fact that two adjacent MWCNTs shared a common graphene.

Effect of pressure on nanocrystalline diamond films deposition by hot (lament CVD technique from CH 4 /H 2 /Ar gas mixture

The effect of pressure on the deposition of nanocrystalline diamond (NCD) Films in a hot filament chemical vapor deposition (IFCVD) system was investigated using CH4/H2/Ar gas mixture. The reactor pressure was found to have the strongest influence on nucleation of nanocrystalline diamond films. The range of Ar concentration in the CH4/H2/Ar mixture that permits the deposition of nanocrystalline diamond (NCD) Film at 40 torr is 90%, while the Ar concentration needed for the transition into nanocrystalline diamond phase is 50% at 5 torr. Such pressure dependence of the nanocrystalline diamond Film growth is suggested to result from two competing effects of pressure on the concentration of reactive species near the Film growth surface, and the C2 density at lower pressure (5 torr) is higher than that at high pressure (40 torr) at the same Ar concentration.