Electronic states and electrical conductivity of the Si(111) native oxide surface adsorbed with electron donor tetrakis(dimethylamino)ethylene.

Electronic states and electrical conductivity of the native oxide Si(111) surface adsorbed with an electron donor tetrakis(dimethylamino)ethylene (TDAE) were investigated using ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy (XPS), and independently driven four-probe conductivity measurements. The formation of positively charged TDAE species is confirmed by the downward shift of the vacuum level by 1.45 eV, the absence of HOMO level in the valence band, and observation of the positively charged state in the N 1s XPS spectra. Si 2p XPS spectra and four-probe conductivity measurements revealed that TDAE adsorption induces an increase in downward band bending and a reduction in electrical resistance of the surface, respectively. The sheet conductivity and the electron density of the surface are 1.1 μS/? and 4.6 × 109 cm-2, respectively, after TDAE adsorption, and they are as high as 350% of the original surface. These results demonstrate that the electron density of the semiconductor surface is successfully controlled by the electron donor molecule TDAE. [ABSTRACT FROM AUTHOR]