Low-temperature scanning tunneling spectroscopy: Kondo effect and surface state lifetimes

We present an overview of the experimental method and physical principles of scanning tunneling microscope (STM) light emission spectroscopy (STM-LES). By this new spectroscopic technique one can obtain the optical emission spectra of specific and individual surface nanostructures that are imaged by the STM. This method has been used to investigate the electronic transitions in surface nanostructures such as the protrusions of porous Si, the quantum wells of a semiconductor, and the rows and valleys of the reconstructed Au(110) surface.