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Electronic properties of semiconductors can be controlled by introduction of appropriate dopants into the bulk lattice. However, in a novel phenomenon known as “surface transfer doping,” free electrons or holes can be generated in undoped semiconductor surfaces, without the introduction of foreign atoms within the lattice, by controlled deposition of thin layer of certain chemical moieties with 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 shows a highly unusual p-type surface conductive layer on an otherwise insulating surface when exposed to ambient air. In this case, surface conductivity develops spontaneously as a result of electron transfer from diamond to an adsorbed water film on the surface. Since then, this effect has been exploited for other systems, such as diamond/C60, graphene/C60, black phosphorus. 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, graphene, gallium nitride and zinc oxide. This presentation will give an overview of the recent progress in this field and its impact on the emerging technologies.
Vidhya Chakrapani is currently an Associate Professor with a joint appointment in Dept. of Chemical and Biological Engineering and Dept. of Physics at Rensselaer Polytechnic Institute. She completed her PhD at Case Western Reserve University in 2007 and went on to postdoctoral studies at Georgia Institute of Technology and Notre Dame Radiation Laboratory. She worked at Tokyo Electron Technology Center for nearly 2 years before moving to RPI. For the past 20 years, her research has focused on the various fundamental and applied aspects of semiconductor electrochemistry, including photocatalysis, electrocatalysis, solar cells, and Li ion batteries. For her work on diamond electrochemistry, she was awarded the Outstanding Young Researcher award from the Sigma Xi Research Society and the Young Investigator awards from the Indian Institute of Science and JNCAR, India. She has published more than 35 papers in this field along with 3 patents.