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Photoemission yield under two-quantum excitation in Si

1981; American Physical Society; Volume: 23; Issue: 3 Linguagem: Inglês

10.1103/physrevb.23.992

1095-3795

M. Bensoussan, J. M. Moison, B. Stoesz, C.A. Sébenne,

Electron and X-Ray Spectroscopy Techniques

It is shown for the first time that under pulsed laser excitation, photoemission from cleaned (7\ifmmode\times\else\texttimes\fi{}7) Si (111) surfaces occurs at photon energies (3.7 to 2.3 eV) below the work function ($\ensuremath{\varphi}=4.6$ eV). We demonstrate its two-quantum origin by: (i) establishing the characteristic flux law, i.e., electron flux proportional to the square of photon flux, over six orders of magnitude; (ii) showing that the two-quantum yield falls very rapidly when photon energy decreases, no photoemission being observed below $\frac{1}{2}\ensuremath{\varphi}$.