Florian Nitze

On the fabrication of crystalline C 60 nanorod transistors from solution

Flexible and high-aspect-ratio C(60) nanorods are synthesized using a liquid-liquid interfacial precipitation process. As-grown nanorods are shown to exhibit a hexagonal close-packed single-crystal structure, with m-dichlorobenzene solvent molecules incorporated into the crystalline structure in a C(60):m-dichlorobenzene ratio of 3:2. An annealing step at 200 °C transforms the nanorods into a solvent-free face-centred-cubic polycrystalline structure. The nanorods are deposited onto field-effect transistor structures using two solvent-based techniques: drop-casting and dip-coating. We find that dip-coating deposition results in a preferred alignment of non-bundled nanorods and a satisfying transistor performance. The latter is quantified by the attainment of an electron mobility of 0.08 cm (2) V(-1) s(-1) and an on/off ratio of > 10(4) for a single-crystal nanorod transistor, fabricated with a solution-based and low-temperature process that is compatible with flexible substrates.

Water Assisted Growth of C-60 Rods and Tubes by Liquid-Liquid Interfacial Precipitation Method

C60 nanorods with hexagonal cross sections are grown using a static liquid–liquid interfacial precipitation method in a system of C60/m-dichlorobenzene solution and ethanol. Adding water to the ethanol phase leads instead to C60 tubes where both length and diameter of the C60 tubes can be controlled by the water content in the ethanol. Based on our observations we find that the diameter of the rods/tubes strongly depends on the nucleation step. We propose a liquid-liquid interface growth model of C60 rods and tubes based on the diffusion rate of the good C60 containing solvent into the poor solvent as well as on the size of the crystal seeds formed at the interface between the two solvents. The grown rods and tubes exhibit a hexagonal solvate crystal structure with m-dichlorobenzene solvent molecules incorporated into the crystal structure, independent of the water content. An annealing step at 200 °C at a pressure <1 kPa transforms the grown structures into a solvent-free face centered cubic structure. Both the hexagonal and the face centered cubic structures are very stable and neither morphology nor structure shows any signs of degradation after three months of storage.

Electronic properties of Cs-intercalated single-walled carbon nanotubes derived from nuclear magnetic resonance

We report on the electronic properties of Cs-intercalated single- walled carbon nanotubes (SWNTs). A detailed analysis of the 13 C and 133 Cs nuclear magnetic resonance (NMR) spectra reveals an increased metallization of the pristine SWNTs under Cs intercalation. The metallization of CsxC materials where x = 0-0.144 is evidenced from the increased local electronic density of states (DOS) n(EF) at the Fermi level of the SWNTs as determined from spin-lattice relaxation measurements. In particular, there are two distinct electronic phases called and and the transition between these occurs around x = 0.05. The electronic DOS at the Fermi level increases monotonically at low intercalation levels x < 0.05 ( -phase), whereas it reaches a plateau in the range 0.05 6 x 6 0.143 at high intercalation levels ( -phase). The new -phase is accompanied by a hybridization of Cs(6s) orbitals with C(sp 2 )orbitals of the SWNTs. In both phases, two types of metallic nanotubes are found with a low and a high local n(EF), corresponding to different local electronic band structures of the SWNTs.