Coil-in-coil carbon nanocoils: 11 gram-scale synthesis, single nanocoil electrical properties, and electrical contact improvement.

Coil-in-coil carbon nanocoils (CNCs) were synthesized by means of acetylene decomposition using nickel nanoparticles as catalysts. The investigations revealed that there are often several CNCs self-assembled in one nanospring. The yield of coil-in-coil CNCs was high up to 11 g in each run at the decomposition temperature of 450 degrees C. CNC nanodevices were fabricated for systematical examinations of charge conduction in the single CNC and in the electrical contacts. A focused laser beam of about 70 mum in diameter was applied for selective annealing CNC nanodevices so as to improve the electrical contacts to the CNC. Our study showed that the selective focused laser annealing technique is an effective route to improve the electrical contacts to the nanodevice. Temperature-dependent CNC resistances are analyzed with the Mott-variable range hopping (VRH) and Efros-Shklovskii VRH model, revealing electron hopping conduction in the disordered CNCs with a characteristic length of about 5-50 nm.