Blunted Tungsten Tip Cleaning by Nitrogen Gas Etching at Room Temperature without Tip Heating and Cooling

For a long time, the ultra-sharp tips are used for high resolution microscope, such as scanning tunneling microscope (STM), atomic force microscope (ATM), field emission scanning electron microscope (FE-SEM). In addition, helium ion microscope (HIM), which has sub-nanometer imaging resolution, employs the tip as gas field ionization source (GFIS) in recent years. There are a lot of required vital conditions of tip fabrication and source characterization for the high performance of microscopes. Among them, tip cleanliness and operation temperature are very essential for the stable and high charged particle beam current. The contaminants on the surface of tip will undoubtedly cause instabilities in the tunnel junction between tip and gases and abruptly increases fluctuation of the charged particle beam current, thus affecting the image quality and noise level. Also, its requirements for liquid nitrogen cooling make the microscope system complicated, expensive maintenance cost and price of apparatus. This study presents a simple and efficient way to clean the blunted tungsten tip using a field-assisted nitrogen etching at room temperature without tip heating and cooling methods.