Scanning Tunneling Spectroscopy

The scanning tunneling microscope (STM) has revolutionized our ability to explore and manipulate atomic-scale solid surfaces. In addition to its unparalleled spatial power, the STM can study dynamical processes, such as molecular conformational changes, by recording current traces as a function of time. It can also be employed to measure the physical properties of molecules or nanostructures down to the atomic scale. Combining STM imaging with measurement of current–voltage (I–V) characteristics [i.e., scanning tunneling spectroscopy (STS)] at similar resolution makes it possible to obtain a detailed map of the electronic structure of a surface. For many years, STM lacked chemical specificity; however, the recent development of STM–IETS (inelastic electron tunneling spectroscopy) has allowed us to measure the vibrational spectrum of a single molecule. This review introduces and illustrates these recent developments with a few simple scholarly examples.