Atomic scale modifications of hydrogen-terminated silicon 2×1 and 3×1 (001) surfaces by scanning tunneling microscope

Abstract

Atomic scale desorption and deposition of hydrogen (H) atoms on Si(001)-(2×1)-H and Si(001)-(3×1)-H surfaces have been studied using clean and H covered tips from a scanning tunneling microscope. We report desorption of H atoms from these surfaces at positive and negative sample bias voltages with a resolution of one to two atomic rows and atomic scale phase transitions from 3×1 structures to 2×1 structures and vice versa. At positive sample bias, phase transitions from the 3×1 to 2×1 structures are accompanied with a large number of dangling bonds on the newly crated 2×1 structures, because the desorption of H from the 2×1 structure occurs at a lower tunnel current than the formation of the phase transition. At negative sample bias <−5V, the situation is reversed with the desorption from the 2×1 structure occurring at a larger tunnel current than the formation of the phase transition, and “clean” local 2×1 structures with few dangling bonds can be achieved. Using H covered tips and increasing the substrate temperatures of Si(001)-(2×1)-H surfaces to ≈400K, opposite local phase transitions from 2×1 structure to 3×1 structures are also reported, but such phase transitions were only observed at negative sample bias.