Electronic properties of semiconductors can be controlled by introduction of appropriate dopants into the bulk lattice. In a recently discovered phenomenon, known as “surface transfer doping,” free electrons or holes can be generated in undoped semiconductor surfaces, without the introduction of foreign atoms, by controlled deposition of thin layer of chemical moieties having appropriate electronic structure. In this type of doping, the nature of electrical conductivity and the direction of electron transfer depend crucially on the relative positions of the Fermi level of semiconductor and the chemical potential of electrons in the surface chemical moieties. This doping phenomenon was first observed in undoped hydrogenated diamond, which showed a p-type surface conductivity when exposed to ambient air.¹ In this case, surface conductivity develops spontaneously as a result of electron transfer from diamond to an adsorbed water film on the surface.^2,3,4 Since then, this effect has been exploited for other systems, such as diamond/C₆₀,⁵ graphene/C_60. In addition, the process has been shown to affect electrical, optical and electrochemical properties of several technologically important materials such as single-walled carbon nanotubes,⁶ graphene,⁷ gallium nitride and zinc oxide.⁸ This presentation will give an overview of the recent progress in this field and its impact on the emerging technologies.

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