Electro-chemical preparation of fine needles for field ion microscopy to observe biomolecules

Field ion microscope (FIM) is a tool for direct observation of atomic structure at a tip of needle electrode. Fine radius of curvature is required to obtain the images with high resolution. An electro-chemical method has been used to prepare the fine needle tip. Using an ac voltage, a tungsten fine tip was prepared in alkaline solution. It was confirmed that the current associated with the electrolysis was an indicator for the process, and reproducible preparation could be made. With the needle prepared in this way, fine atomic images could be obtained. Attaching other molecule, such as DNA molecules, on the needle gives characteristic images.