Scanning Tunneling Microscopy (STM)
In Scanning Tunneling Microscopy (STM), an electrically-biased tip is scanned very close to a surface (about an atomic diameter away). The current flow between the tip and the sample (due to quantum tunneling) strongly depends on the tip-surface gap; this relationship can be used to generate a surface topography map. Atomic-scale topographic resolution is achievable. All samples for STM must be at least somewhat electrically conductive.