Single Si atoms can be deposited onto a Si(111)-7X7 sample surface from the tip of a scanning tunneling microscope, the Si atoms to be deposited being previously picked up by the tip from another place on the sample surface. The crystallographic position of these deposited Si atoms changes as their density increases. The deposited Si atoms can be re-removed by picking them up again with the tip, the substrate atomic arrangement remaining unperturbed. It is also possible to fill Si atom vacancies on the sample surface with a Si atom deposited from the tip.