SCANNING TUNNELING MICROSCOPE INDUCED CRYSTALLIZATION OF FULLERENE-LIKE MOS2

Amorphous precursors, like MoS3 (WS3), were shown before to be an idea l precursor for the growth of inorganic fullerene-like material in a r ather slow crystallization process which lasts anything from 1 h at 80 0-900 degrees C-1,C-2 to a few years at ambient conditions.(3,4) Using a few microsecond short electrical pulses from the tip of a scanning tunneling microscope, crystallization of amorphous MoS3 (a-MoS3) nanop articles, which were electrodeposited on a Au substrate into MoS2 nano crystallites with a fullerene-like structure (IF-MoS2), is demonstrate d. The (outer) shell of each nanocrystallite is complete, which sugges ts that the reaction extinguishes itself upon completion of the crysta llization of the MoS2 layers. A completely different mode of crystalli zation is observed in the case of continuous a-MoS3 films. Here tiny ( 2-3 nm thick) 2H-MoS2 platelets are observed after the electrical puls e, suggesting a very rapid dissipation of the thermal energy through t he gold substrate, in the continuous domain. Since the reaction mechan ism in both cases is believed to be the same, it is likely that the ma in stimulus for the chemical reaction/crystallization of the IF materi al results from the slow heat dissipation from the nanoparticle. The e xothermicity of the chemical reaction may further promote the rate of the process.