Study on a Novel Peeling of Nano-Particle (PNP) Process for Localized Material Removal on a 4H-SiC Surface by Controllable Magnetic Field.

This study proposes a novel process called peeling of nano-particle (PNP) to remove material locally on a hard material surface, such as silicon carbide (SiC), diamond, and gallium nitride (GaN), using the magnetic nano-particles in an aqueous solution controlled by magnetic fields. By the concept of the PNP process, magnetic fields are generated by two solenoid coils, which are sandwiched between the hard material sample, to pull the magnetic nano-particles to adhere to and then peel the material from the sample surface. In this experiment, iron (II, III) oxide (Fe₃O₄) particles with a diameter size in the range of 50–100 nm were dispersed in water, and the pH value was adjusted to 10 by potassium hydroxide (KOH). The particles were magnetically controlled on the silicon carbide (4H-SiC) surface by the magnetic fields at approximately 17 mT. To confirm the contact phenomenon of the Fe₃O₄ particles on the 4H-SiC surface during the PNP process, an optical system was developed by applying evanescent field microscopy to limit the observation range to approximately 300 nm from the 4H-SiC surface. According to the experimental observed results, the control phenomenon of two examples of Fe₃O₄ particles could be observed through their scattering light, which relates to the magnetic field generating sequence wherein the particles were magnetically pulled in and out of the 4H-SiC surface in the limit range of the evanescent field. During the particle pull to the surface, particles were able to be tracked in the X–Y directions during the approach to the 4H-SiC surface. The Brownian motion ranges in all directions of the particles decreased when the particles approached close to the surface due to the pulling magnetic field. Moreover, the magnetic field enforced the magnetic moment of the particle and limited their rotation. [ABSTRACT FROM AUTHOR]