Combined Theoretical and Experimental Study of Band-Edge Control of Si through Surface Functionalization

Abstract

The band-edge positions of H-, Cl-, Br-, methyl-, and ethyl-terminated Si(111) surfaces were investigated through a combination of density functional theory (DFT) and many-body perturbation theory, as well as by photoelectron spectroscopy and electrical device measurements. The calculated trends in surface potential shifts as a function of the adsorbate type and coverage are consistent with the calculated strength and direction of the dipole moment of the adsorbate radicals in conjunction with simple electronegativity-based expectations. The quasi-particle energies, such as the ionization potential (IP), that were calculated by use of many-body perturbation theory were in good agreement with experiment. The IP values that were calculated by DFT exhibited substantial errors, but nevertheless, the IP differences, i.e., IP_(R–Si(111))–IP_(H–Si(111)), computed using DFT were in good agreement with spectroscopic and electrical measurements.

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