Direct writing in Si with a scanning tunneling microscope

Using the W tip of a scanning tunneling microscope, indentations with diameters of 2–10 nm have been made directly in Si (110) and Si (001) surfaces. It is possible to create and image (‘‘write and read’’) arbitrary lines and bit patterns reproducibly with a single tip, without degrading its sharpness. The method does not require ideally flat surfaces and the indentations, when made in Si and kept in ultrahigh vacuum, are stable in time.