FIELD ION APPEARANCE SPECTROSCOPY AT SILICON SURFACES

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FIELD ION APPEARANCE SPECTROSCOPY AT SILICON SURFACES

W. Schmidt, M. Lovisa, J. Block

To cite this version:

W. Schmidt, M. Lovisa, J. Block. FIELD ION APPEARANCE SPECTROSCOPY AT SILICON SURFACES. Journal de Physique Colloques, 1984, 45 (C9), pp.C9-263-C6-264.

�10.1051/jphyscol:1984944�. �jpa-00224425�

JOURNAL DE PHYSIQUE

Colloque C9, supplément au n°12, Tome 45, décembre 198* page C9-263

FIELD ION APPEARANCE SPECTROSCOPY AT SILICON SURFACES

W.A. Schmidt, M.F. L o v i s a and J . H . Block

Fritz-Haber-Institut der Max-Planek-Gesellschaft, Favadayweg 4-6, D-1000 Berlin 3Z, F.R.G.

Résume- Nous présentons des distributions énergétiques inté- grales d'ions obtenus par émission de champ à partir de surfaces de si- licium au moyen de gaz nobles et d'hydrogène. Nous analysons à partir des résultats, le processus d'émission de champ ionique en tenant compte de la structure de bande de surface du silicium.

Abstract - We present field ion integral energy distributions for noble gases and hydrogen obtained at silicon surfaces. From the results we analyse the field ionization process with respect to the surface-band structure of silicon.

The onset and shape of integral energy distributions for field ionized hydrogen, argon and krypton were examined using p-type [111]-oriented silicon whiskers at 298 K. Such energy distributions were compared with energy distributions for the same field ionized gases measured with a metal emitter ( A u ) . In this way, it was possible to determine the energetically deepest empty states within the band structure of the silicon surface which are available to the tunneling electrons.

The main experimental results are as follows:

(i) i'rj hydrogen field ionization at silicon surfaces, the onset of the H„ energy distribution was found to be the same as with metals and independent of the applied field. There were shape differences of the energy distributions in the near onset range between sili- con and metal emitters.

(ii) in noble gas fie|d ionization at silicon surface, relatively sharp onsets of the Ar or Kr energy distributions were found. They were remarkably higher than for metals and decreased when the ap- plied field was increased. Even at the highest fields accessible, the onsets for silicon were above the onset for metals by about 0.2 Volt.

(iii)noble gas field ionization at the silicon surface in the presence of hydrogen showed Ar or Kr energy distribution onsets which were the same as for metals. There were again shape differences, as in the case of the Ho energy distribution.

The results noted in (i) and (i i i) can be explained by considering the reaction of hydrogen with silicon. The surface states, in this case, are removed from the energy levels of the bulk band gap. Due to the electric field, the valence band bends to above the Fermi level. Then, tunneling can occur into states as deep as in the case of a metal.

Furthermore, the smooth onset of the Ho energy distribution found with silicon is an indication of a double energy distribution, due to the bulk ba.nd structure. This also explains the onset behaviour of the Ar and Kr energy distribution in the presence of hydrogen.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984944

C9-264 JOURNAL DE PHYSIQUE

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