Hydrogen Chemisorption on Si Surfaces Analyzed by Magnetic-Sector, Atom-Probe, Field-Ion Microscopy

An atom-probe field-ion microscope was successfully employed for the first time to study semiconductor Si surfaces. Using a magnetic-sector type we have observed pure silicon ${\mathrm{Si}}^{+}$, monohydride Si${\mathrm{H}}^{+}$, and dihydride Si${\mathrm{H}}_2^{+}$, ions from the well-ordered H-covered (111) and (110) planes, and pure silicon ${\mathrm{Si}}^{+}$, monohydride Si${\mathrm{H}}^{+}$, and silane Si${\mathrm{H}}_4^{+}$ ions from the disordered (311) areas. This observation is taken as the evidence for the formation of the silicon dihydride and trihydride surface phases suggested by recent ultraviolet photoemission studies.