The scanning tunneling microscope (STM) is a powerful tool that allows scientists to observe and manipulate individual atoms and molecules on surfaces. While the STM can manipulate atoms, it does not typically "cut" atoms from a source material in the conventional sense. However, it can be used to dislodge atoms from a surface and move them to a desired location. Here's a general process of how this can be achieved:
Preparation: The STM operates under ultra-high vacuum conditions to minimize any interference from the environment. The sample, which contains the atoms of interest, is prepared by depositing it on a conductive substrate.
Scanning: The STM consists of a sharp tip made of a conductive material, which is brought close to the surface of the sample. The tip is attached to a piezoelectric scanner, allowing for precise movement in the x, y, and z directions. A small voltage is applied between the tip and the surface.
Tunneling Current: When the tip is brought close enough to the surface, the quantum tunneling effect occurs. A small electrical current, known as the tunneling current, flows between the tip and the surface. The magnitude of this current is exponentially dependent on the distance between the tip and the surface.
Feedback Mechanism: The STM maintains a constant tunneling current by using a feedback mechanism. As the tip scans across the surface, the height variations of the atoms cause the tunneling current to change. The feedback mechanism adjusts the tip's position to maintain a constant current, creating a topographic map of the surface.
Atom Manipulation: Using the STM, it is possible to manipulate individual atoms. By precisely positioning the STM tip above a specific atom, a voltage pulse can be applied to the tip. This pulse can induce an electrostatic force on the atom, causing it to move or dislodge from the surface.
Atom Transfer: Once an atom is dislodged, it can be transferred to a desired location on the surface by carefully controlling the STM tip's movement. The dislodged atom can be moved by scanning the tip above the target location and using the electrostatic force to place the atom in the desired position.
It's important to note that the process of manipulating individual atoms using an STM requires great precision and control. The specific details and techniques employed may vary depending on the experimental setup and the properties of the atoms and the surface being studied.