The electronic effects of doping

A substitutional donor or acceptor in a crystalline semiconductor results in the formation of a shallow electronic state. For the specific case of the donor, the extra electron is bound to the charged 

The central cell correction results in a binding energy of 40 meV for phosphorus and 45 meV for arsenic in crystalline silicon and the boron acceptor energy is 45 meV. 

The Coulomb interaction between the electron and the donor core is, of course, present in an amorphous semiconductor and binds an electron in much the same way, so the shallow donor state is preserved. The effective mass theory for dopants cannot be applied directly to amorphous semiconductors, because it is formulated in terms of the momentum-space wavefunctions of the crystal. It is not immediately obvious that the effective mass has any meaning in an amorphous 

The expectation that substitutional impurities behave as effective mass donors and acceptors in a Si H is borne out by experiment. However, doping also induces deep states in a-Si H and these are discussed first. 

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D.L. Carroll, X. Blase, J.C. Charlier, P. Redlich, P.M. Ajayan, S. Roth, and M. Ruhle, Effects of nanodomain formation on the electronic structure of doped carbon nanotubes. Phys. Rev. Lett. 81, 2332-2335 (1998). 

Since insulating magnesium oxide can be doped to form n-type or p-type semiconductors at moderate temperatures (72), we have here a first example of the electronic effect of a semiconducting support. However, it is unknown what type of conduction was present during the catalytic reaction in the originally undoped specimens used for the preceding experiments. 

Zhou, X.D., Huebner, W., and Anderson, H.U., Size effect on the electronic properties of doped and undoped ceria, in Defects and Diffusion in Ceramics An Annual Retrospective VII, Vols. 242-244, Trans Tech Publications Ltd., Zurich-Uetikon, Switzerland, 2005, pp. 277-289. 

Silicon alloyed with a copper catalyst and promoter substances reacts with methyl chloride (at temperatures around 300 °C) to give a mixture of methylchlorosilanes in the industrial direct synthesis. Dimethyldichlorosilane represents the most important target in this process. Since Rochow [1] and Mtiller [2] discovered this direct synthesis route for the silicon-promoter-catalyst system, many investigations were done to increase the activity as well as the selectivity and to clarify the mechanism. Zinc, tin, and phosphorus, beside other substances, were found to give effects [3-6]. The goal of this research work is to find out whether there are relationships between the electronic effect of phosphorus, tin, boron, or indium doping of silicon and its reactivity as well as selectivity in direct synthesis. Characterization of the electronic state of the variously doped silicon relies on photo-EMF measurements. 

As already set out above electronic and ionic conductivities of LiFeP04 can be influenced by doping with aliovalent cations. But due to the opposite effect of doping on positive (h ) and negative (Vy) charge carriers neither donor nor acceptor doping is able to greatly increase O as shown in Fig. 8.13. 

The enantioselective hydrogenation of a,p-unsaturated acids or esters, using 5wt% Pt/Al203 or Pd/Al203 commercial catalysts doped with cinchonidine (CD), was deeply investigated to evidence the specific activity of Pd or Pt and the role of the reaction parameters and solvent polarity. Finally, the steric and electronic effects of different substituent groups were also studied. 

The N-doped carbons with a nanotube backbone combine a moderate presence of micropores with the extraordinary effect of nitrogen that gives pseudocapacitance phenomena. The capacitance of the PAN/CNts composite (ca. 100 F/g) definitively exceeds the capacitance of the single components (5-20 F/g). The nitrogen functionalities, with electron donor properties, incorporated into the graphene rings have a great importance in the exceptional capacitance behavior. 

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