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Temperature dependence of surface conductivity and tunneling density of states of the Si(111)-7x7 surface in slightly-doped crystals


A. B. Odobesku, A. A. Rogozin, S. V. Zaitsev-Zotov

Kotel'nikov Institute of Radio Engineering and Electronics of RAS

Received September 4, 2012


Abstract. The tunneling surface density of states and surface conductivity of the Si(111)-7x7 structure (n-type with ρ = 1 Ωcm) have been studied using scanning tunneling  microscopy and spectroscopy. Our results indicate the existence of the energy gap in surface states at Fermi level, 2Δ = 40±10 meV at T = 5K, which smoothly blurs with the increase of the temperature The energy gap disappears at T>40K, due to the thermal fluctuation. The temperature-dependent surface conductivity measurements of the Si(111)-7x7 structure in the temperature region 35-100K were performed. The dependence of the surface conductivity follows the activation law with the activation energy 25 meV corresponding the data obtained from tunneling spectroscopy measurements. Our results indicate absence of the phase transition around T ~ 20 K suggested earlier.

Keywords: Si(111)-7x7 structure, scanning tunneling  microscopy, scanning tunneling  spectroscopy, surface conductivity.