A scanning tunneling microscope (STM) is a nanoscale imaging tool used to observe and manipulate materials at an atomic level. It operates based on the principle of quantum tunneling and employs a sharp metallic tip that scans the surface of a sample. The tip is brought extremely close to the surface, within a few angstroms, and a small bias voltage is applied between the tip and the sample.
As the tip moves across the sample, it occasionally encounters regions of higher electron density. This causes a small number of electrons to "tunnel" from the tip to the sample or vice versa, resulting in a measurable electrical current. The microscope registers these changes in current and maps them into a three-dimensional image, providing detailed information about the sample's topography and electronic properties at the atomic scale.
STM is capable of achieving atomic resolution, making it an essential tool in various scientific disciplines such as material science, nanotechnology, and surface chemistry. It allows researchers to observe the arrangement of individual atoms on a solid surface, study surface defects and impurities, and investigate surface processes, such as adsorption and desorption.
Moreover, the STM can be used for manipulation at the atomic level. By precisely controlling the position of the tip, scientists can push or pull individual atoms, creating nanostructures with desired properties or investigating the fundamental interactions between atoms.
In summary, the scanning tunneling microscope is a powerful instrument that enables imaging, analysis, and manipulation of materials at the atomic level, contributing significantly to the advancement of nanoscience and technology.
