A simple method for simulating scanning tunneling images

Real-space observation of single atoms and electron surface states lies at the heart of scanning tunneling microscopy. The resolution of atomic structures depends on quantum mechanical features such as three-dimensional tunneling, the Pauli principle, the possibility of electron resonances, and the importance of multiple scattering events, which allow the current carrying electrons to detect single atoms and explore electronic properties of surfaces. We present a simple calculation that leads directly to experimentally observable quantities. The starting point of the calculation is the treatment of the scanning tunneling microscope (STM) as an open quantum system, with the tip being a point-like source (or sink) of electrons. Our STM image simulations of corral-like adsorbate structures bear strong resemblance to the experimental results by Crommie et al. [Science 262, 218–220 (1993); Physica D 83, 98–108 (1995)].