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  Rietwyk, K.J.; Smets, Y.; Bashouti, M.; Christiansen, S.H.; Schenk, A.; Tadich, A.; Edmonds, M.T.; Ristein, J.; Ley, L.; Pakes, C.I.: Charge Transfer Doping of Silicon. Physical Review Letters 112 (2014), p. 155502/1-5

10.1103/Phys.RevLett.112.155502

Abstract:
We demonstrate a novel doping mechanism of silicon, namely n-type transfer doping by adsorbedorganic cobaltocene (CoCp2
) molecules. The amount of transferred charge as a function of coverage is monitored by following the ensuing band bending via surface sensitive core-level photoelectron spectroscopy. The concomitant loss of electrons in the CoCp2 adlayer is quantified by the relative intensities of chemically shifted Co2p components in core-level photoelectron spectroscopy which correspond to charged and neutral molecules. Using a previously developed model for transfer doping, the evolution in relative intensities of the two components as a function of coverage has been reproduced successfully. A single, molecule-specific parameter, the negative donor energy of −ð0.50  0.15Þ eV suffices to describe the self-limiting doping process with a maximum areal density of transferred electrons of 2 × 1013 cm−2 in agreement with the measured downward band bending. The advantage of this doping mechanism over conventional doping for nanostructures is addressed.