The scanning tunneling microscope has been used to desorb hydrogen from hydrogen-terminated silicon (100) surfaces. As a result of control of the dose of incident electrons, a countable number of desorption sites can be created and the yield and cross section are thereby obtained. Two distinct desorption mechanisms are observed: (i) direct electronic excitation of the Si-H bond by field-emitted electrons and (ii) an atomic resolution mechanism that involves multiple-vibrational excitation by tunneling electrons at low applied voltages. This vibrational heating effect offers significant potential for controlling surface reactions involving adsorbed individual atoms and molecules.

https://science.sciencemag.org/content/sci/268/5217/1590.full.pdf

Atomic scale desorption through electronic and vibrational excitation mechanisms

Photoemission studies of adsorbed oxygen and oxide layers

Nanoscale patterning of the hydrogen terminated Si(100)‐2×1 surface has been achieved with an ultrahigh vacuum scanning tunneling microscope. Patterning occurs when electrons field emitted from the probe locally desorb hydrogen, converting the surface into clean silicon. Linewidths of 1 nm on a 3 nm pitch are achieved by this technique. Local chemistry is also demonstrated by the selective oxidation of the patterned areas. During oxidation, the linewidth is preserved and the surrounding H‐passivated regions remain unaffected, indicating the potential use of this technique in multistep lithography processes.

https://works.bepress.com/t_shen/46/download/

Nanoscale patterning and oxidation of H‐passivated Si(100)‐2×1 surfaces with an ultrahigh vacuum scanning tunneling microscope

Evaluation of the sp2/sp3 ratio in amorphous carbon structure by XPS and XAES

A time‐of‐flight atom‐probe field‐ion microscope has been developed which uses nanosecond laser pulses to field evaporate surface species. The ability to operate an atom‐probe without using high‐voltage pulses is advantageous for several reasons. The spread in energy arising from the desorption of surface species prior to the voltage pulse attaining its maximum amplitude is eliminated, resulting in increased mass resolution. Semiconductor and insulator samples, for which the electrical resistivity is too high to transmit a short‐duration voltage pulse, can be examined using pulsed‐laser assisted field desorption. Since the electric field at the surface can be significantly smaller, the dissociation of molecular adsorbates by the field can be reduced or eliminated, permitting well‐defined studies of surface chemical reactions. In addition to atom‐probe operation, pulsed‐laser heating of field emitters can be used to study surface diffusion of adatoms and vacancies over a wide range of temperatures. Examples demonstrating each of these advantages are presented, including the first pulsed‐laser atom‐probe (PLAP) mass spectra for both metals (W, Mo, Rh) and semiconductors (Si). Molecular hydrogen, which desorbs exclusively as atomic hydrogen in the conventional atom probe, is shown to desorb undissociatively in the PLAP. Field‐ion microscope observations of the diffusion and dissociation of atomic clusters, the migration of adatoms, and the formation of vacancies resulting from heating with a 7‐ns laser pulse are also presented.

Pulsed-laser atom-probe field-ion microscopy

Comparison of the CKLL first-derivative auger spectra from XPS and AES using diamond, graphite, SiC and diamond-like-carbon films

Esca studies of Ga, As, GaAs, Ga2O3, As2O3 and As2O5

Surface structures and work functions of the LaB6 (100), (110) and (111) clean surfaces

We have identified the monohydride Si(001)-(2\ifmmode\times\else\texttimes\fi{}1):H surface and the dihydride $\mathrm{Si}(001)\ensuremath{-}(1\ifmmode\times\else\texttimes\fi{}1)\ensuremath{\mathbin{::}}2\mathrm{H}$ surface by angle-resolved electron-energy-loss spectroscopy and elastic low-energy electron diffraction. On the monohydride (2\ifmmode\times\else\texttimes\fi{}1):H surface the ${S}_{3}$ transition from the back-bond surface state was distinctly observed although the ${S}_{1}$ transition from the dangling-bond surface state disappeared, while on the dihydride $(1\ifmmode\times\else\texttimes\fi{}1)\ensuremath{\mathbin{::}}2\mathrm{H}$ surface both the ${S}_{3}$ and the ${S}_{1}$ transitions completely disappeared. These facts show that on the monohydride surface the subsurface strain due to dimerization remains; on the other hand, on the dihydride surface the strain is healed out. The hydrogen-induced transitions for the two surfaces were clearly distinguished; the transition energy for the (2\ifmmode\times\else\texttimes\fi{}1):H surface (S${\mathrm{H}}_{1}$) was 8.0 eV and that for the $(1\ifmmode\times\else\texttimes\fi{}1)\ensuremath{\mathbin{::}}2\mathrm{H}$ surface (S${\mathrm{H}}_{2}$) increased from 7.0 to 7.5 eV with increasing $|{k}_{\ensuremath{\parallel}}|$ due to dispersion. The present results support and develop the models for the monohydride and the dihydride surfaces proposed by Sakurai and Hagstrum.

Electronic structures of the monohydride (2×1):H and the dihydride (1×1)&#87592H Si(001) surfaces studied by angle-resolved electron-energy-loss spectroscopy

Shogo Nakamura

Papers

Comparison of the CKLL first-derivative auger spectra from XPS and AES using diamond, graphite, SiC and diamond-like-carbon films

Esca studies of Ga, As, GaAs, Ga2O3, As2O3 and As2O5

Surface structures and work functions of the LaB6 (100), (110) and (111) clean surfaces

Electronic structures of the monohydride (2×1):H and the dihydride (1×1)&#87592H Si(001) surfaces studied by angle-resolved electron-energy-loss spectroscopy

X-ray photoemission study of the initial oxidation of the cleaved (110) surfaces of GaAs, GaP and InSb