RESUMEN
We show that blister-based-laser-induced forward-transfer can be used to cleanly desorb and transfer nano- and micro-scale particles between substrates without exposing the particles to the laser radiation or to any chemical treatment that could damage the intrinsic electronic and optical properties of the materials. The technique uses laser pulses to induce the rapid formation of a blister on a thin metal layer deposited on glass via ablation at the metal/glass interface. Femtosecond laser pulses are advantageous for forming beams of molecules or small nanoparticles with well-defined velocity and narrow angular distributions. Both fs and ns laser pulses can be used to cleanly transfer larger nanoparticles including relatively fragile monolayer 2D transition metal dichalcogenide crystals and for direct transfer of nanoparticles from chemical vapour deposition growth substrates, although the mechanisms for inducing blister formation are different.
RESUMEN
Using electron microscopy and in situ Raman spectroscopy we investigate carbon nanotube growth from ethylene on iron catalyst islands patterned on top of Mo electrodes, using a highly localized resistive on-chip-heating technique. A clear transition is observed between multi-walled and single-walled nanotube growth as the local temperature of the heater is increased. This can be rationalized in terms of the balance between incoming carbon flux and diffusion through the catalyst particle. The observed changes in heater performance on exposure to the hydrocarbon gas are explored and related to the formation of molybdenum carbide, leading to a rapid change in resistivity and heating power that increases the local temperature of the heater by up to 100 °C. This provides optimum conditions for nanotube growth after an incubation time that depends on the carbon flux.
RESUMEN
Ambient room temperature growth of aligned multi-walled carbon nanotube arrays on micrometer scale local heaters is demonstrated. High growth rates of up to 8.8 microm per second have been achieved and the growth has been monitored in situ using optical microscopy. The growth starts and ends abruptly over the length of the local heater. The terminal length of the nanotubes shows a clear dependence on growth temperature and small inhomogeneities in temperature across the heater are seen to lead to interesting microstructure of the arrays. The activation energy for growth was seen to be consistent with earlier reports for acetylene growth of nanotubes on iron catalysts.