MANIPULATING ATOMS ONE BY ONE WITH A SCANNING TUNNELING MICROSCOPE

By using an STM operated in ultrahigh vacuum, we can extract single Si atoms from any predetermined positions of the Si(111)-(7 x 7) surface through field evaporation. This technique enables us to create novel atomic-scale structures, and even to fabricate a single atom groove an d chain on the surface. The extracted Si atoms can be redeposited onto the surface, although the crystallographic position of these deposite d Si atoms changes as their density increases. We have demonstrated th at natural Si vacancy defects existing on the surface can be repaired by this technique. The deposited Si atoms can be reremoved by picking them up again with the tip, the substrate atomic arrangement remaining unperturbed. We can also remove individual hydrogen atoms from hydrog en-passivated Si(100)-(2 x 1) surfaces. A chain with equal separation of Si dimers produced by hydrogen desorption has been created. These r esults demonstrate the potential of STM for the construction of electr onic devices with atomic dimensions.