How many volts are applied between the tip and sample in a scanning tunneling microscope?

In a scanning tunneling microscope, a small voltage is typically applied between the probe tip and the sample surface to facilitate the tunneling of electrons. While the specific voltage can vary depending on the application, the instrument is generally described as using a small voltage for standard imaging purposes.1

In specialized applications, such as manipulating atoms or enhancing etching rates, higher voltages may be utilized. For example, researchers have applied a voltage of four volts to create a strong electric field capable of removing atoms from the tip to deposit them onto a substrate.1