An Update on Scanning Force Microscopies

摘要

Scanning probe microscopies are quickly becoming routine methods in many laboratories. The ability to probe the microscopic and nanoscopic structure of surfaces in a variety of ambient conditions with a low-maintenance instrument that sits on a benchtop has contributed to the popularity of these techniques. Scanning tunneling microscopy (STM), invented in 1982, was the first technique capable of directly imaging surface atoms in real space. Although this instrument has been miniaturized, multiplexed, and adapted to many environments, there have been few major innovations since its invention. The same cannot be said of atomic force microscopy (AFM), invented in 1986. Whereas the scanning tunneling microscope functions by scanning a sharp metal tip over the surface of a conducting or semiconducting sample, a force microscope does not require a tip or a sample to be conductive. Therefore, virtually all materials can be imaged using variations of force microscopy. Instead of using a tunneling current to sense the proximity of the scanning tip to the surface, force microscopies take advantage of the variety of short- and long-range forces between two masses (e.g., van der Waals, magnetic, and electrostatic forces). Force microscopes image a sample by scanning a probe mounted on a cantilever across a sample surface and then detecting the changes in the forces between the tip and the surface by measuring the deflections of the cantilever. In this article we will describe the evolution of the atomic force microscope and its many variations, and survey applications in chemistry, physics, and biology.