Configuration control of carbon nanotube probe in atomic force microscopy

To precisely control the nanotube probe's length and orientation, focused ion beam (FIB) milling and irradiation processes are utilized in the study. The carbon nanotube (CNT) probes' length is optimized by FIB milling and the end of the CNT probe after FIB processing is found to be a round end with a fullerenelike cap. Using ion beam irradiations method, the carbon nanotube probes are bended and aligned to the desired orientation due to the strain introduced by the ion beam and CNT's excellent plastic ability as well. The evaluation of carbon nanotube probe's metrology performance is also made by correlating CNT probe structures with the probe's atomic force microscopy (AFM) images resolution. It is found that the CNT probe can well overcome the bending response effect on the image resolution if its lateral force constant is larger than 0.086 N/m and CNT probe's angle is less than 30 degrees. The nanotube probe after FIB alignment shows high image resolution, and it can detect an edge with vertical angle of 88.374 degrees, which a common pyramid-shaped AFM probe is not capable of doing. It is also confirmed that the probes with fullerenelike cap end show higher imaging resolution than those with an open end.