Near-Field Scanning Microwave Microscopy: An Emerging Research Tool for Nanoscale Metrology

On 29 December 1959 at the annual meeting of the American Physical Society, Richard Feynman gave a lecture at the California Institute of Technology titled "There Is Plenty of Room at the Bottom: An Invitation to Enter a New Field of Physics." This memorable lecture has since become very famous as it predicted and envisioned the current era of nanoscience and nanotechnology. The atomic level represents a totally new world of fresh opportunities for design and engineering due to the new physics available at such a small scale. Feynman mentions this in his lecture, "Atoms on a small scale behave like nothing on a large scale, for they satisfy the laws of quantum mechanics" [1]. This new physics allows the manipulation of matter atom by atom. As Feynman further states, "The principles of physics, as far as I can see, do not speak against the possibility of maneuvering things atom by atom. It is not an attempt to violate any laws; it is something, in principle, that can be done; but in practice, it has not been done because we are too big" [1]. Feynman was right, and quantum mechanics continues to play a crucial role in miniaturization of technology. But advances in nanotechnology are not based purely on knowledge of the theory. Today we are realizing that all this "plenty of room at the bottom" has brought a great need for complex and ingenious metrology tools that accompany our knowledge of quantum mechanics. These metrology tools are necessary for atomic-scale manipulation as well as the characterization of each atom and its interaction with the environment. Feynman's lecture envisioned the need for significantly improved metrology tools. For example, he discussed improving the electron microscope by 100-fold. Today, in addition to the scanning electron microscope (SEM), we have the atomic force microscope (AFM), the scanning tunneling microscope (STM), and the near-field scanning optical microscope (NSOM), among many other metrology tools used for the advancement of nanotechnology [2]-[4], which Feynman did not foresee. These metrology tools also function as a platform for engineering novel atomic- and molecular-scale devices. This means performing logical operations with a single atom or molecule, manipulation of DNA molecules for information storage, or putting together nanomachines [2]-[4].