Doping methods

A second doping method is the substitution of an impurity atom with a different valence state for a carbon atom on the surface of a fullerene molecule. Because of the small carbon-carbon distance in fullerenes (1.44A), the only species that can be expected to substitute for a carbon atom in the cage is boron. There has also been some discussion of the possibility of nitrogen doping, which might be facilitated by the curvature of the fullerene shell. However, substitutional doping has not been widely used in practice [21]. 

The most productive group in the networks field is the group of Tomoji Kawai from Osaka that pubhshed an extended series of experiments on different networks and with various doping methods [69, 70, and references therein]. In one of their early experiments they measured the conductivity of a single bundle [67]. This was done in a similar way to the de Pablo experiment [58] (see Fig. 7), placing the bundle between a metal-covered AFM tip on one side of the molecule and under a metal electrode that covered the rest of the bundle (see Fig. 9). The conductivity of a poly(dG)-poly(dC) bundle was measured as a function of length (50-250 nm) and was compared with that of a poly(dA)-poly(dT) bundle. The results showed a very clear... 

As mentioned in the preceding section the mobility of degenerately-doped zinc oxide (as well as of other TCO materials and semiconductors) is limited by ionized impurity scattering in homogeneously-doped materials. Since about 30 years it is well known that the mobility can be increased by the so-called modulation doping method, introduced by Dingle et al. [179] for GaAs/C.ai, Af As superlattice structures (for a review see [180]). 

Zhu, J.F., Z.G. Deng, F. Chen, J.L. Zhang, H.J. Chen, M. Anpo, J.Z. Huang and L.Z. Zhang (2006). Hydrothermal doping method for preparation of Cr3+ —Ti02 photocatalysts with concentration gradient distribution of Cr3. Applied Catalysis B-Environmental, 62(3 1), 329-335. 

Fig. 18.18 Optical absorption spectra of Cr-doped TiOj prepared by (a) ion-implantation method and (b) chemically doping method (After Anpo et al. 2001)...

The occurrence of etch rate reduction on highly boron doped materials appears to be independent of doping methods, whether by solid-source diffusion, epitaxial growth, or ion implantation. However, the boron concentration at which significant reduction occurs is different for different methods of doping. The critical boron concentration for etch rate reduction to occur is affected by the defect density in different doped materials. It is found that for similar boron concentrations the amount of etch rate reduction in KOH solutions decreases with increasing defect densityIn... 

Ultrapure silicon has largely supplanted germanium in micro- and power-electronics (integrated circuits, microchips, thyristors, transistors, rectifiers etc.). Silicon accounts for more than 90% of the semiconductor market. There are a number of reasons for the dominance of silicon. Silicon forms stable Si02-protective layers, which can be removed by simple etch processes. This is the basis on which the etch and doping methods are developed, which permit an extremely high density of electronic components e.g. in microprocessors or memory chips. 64 MB memory chips can be currently produced in this way. 

Inorganic Metal oxide materials Base single or mixed metal oxides Deposition method and conditions of base metal oxide(s) Annealing method and conditions Dopant(s) Doping method and conditions Purity of materials... 

A possible influence of the doping method on the behaviour of the different samples was eliminated by using an "alumina" doped sample as a reference. 

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