Site-Specific Synthesis of Conductive Graphitic Nanomaterials on a NiFe Thin Film by Localized Laser Irradiation

Abstract

We report on a facile and low-cost method for the site-specific fabrication of carbon microelectrodes on a NiFe thin film-coated substrate by laser-induced heating of the NiFe layer immersed in ethanol. Raman spectroscopy analysis of the carbon materials synthesized confirms that, after optimization of the laser heating conditions (in terms of laser power, irradiation time, and the number of radiation bursts), the G band peak in the Raman spectra is increased and sharpened and the D/G ratio improved. In addition, from the scanning electron microscopy and energy-dispersive X-ray spectroscopy measurements, we find that the laser-irradiated site is rich in particle-like graphitic nanomaterials with nano-sized grains that are densely distributed on the NiFe substrate. Furthermore, conductive atomic force microscopy measurements show that optimized irradiation conditions enable not only the localized formation of low-D/G-Raman-peak-ratio graphitic nanomaterials with good conductivity but also an increase of the current flow in the laser-irradiated area, reaching current values much higher than that of the bare NiFe thin film. From these results, we conjecture that nanocrystalline-like graphitic nanomaterials with fewer structural defects and good conductivity are synthesized in the laser-irradiated area. This laser-induced graphitic nanomaterials synthesis method can potentially be adapted to directly and locally form carbon microelectrodes on magnetic thin films, offering unique advantages for the development of micromagnetic devices.