Crystal doping

The Bolir radius is very large, 3-5 nm, and tlie shallow impurity wavefunction extends over a large portion of the crystal. Doping up to tlie Tnetallic limit consists in implanting a sufficiently high concentration of donors so tliat tlie shallow-donor wavefunctions overlap, creating a half-filled impurity band in which tlie electrons move freely. 

Materials. Beside inorganic materials (eg, barium chloride/fluoride crystals, doped with 0.05% samarium), transparent thermoplasts are preferred for the PHB technique, eg, poly (methyl methacrylate) (PMAIA), polycarbonate, and polybutyral doped with small amounts of suitable organic dyes, organic pigments like phthalocyanines, 9-arninoacridine, 1,4-dihydroxyanthraquinone [81-64-1] (quinizarin) (1), and 2,3-dihydroporphyrin (chlorin) (2). 

Qi, H. and Hegmann, T. (2006) Formation of periodic stripe patterns in nematic liquid crystals doped with functionalized gold nanopartides. Journal of Materials Chemistry, 16, 4197-4205. 

A further group of interesting experiments to be done is related to the double acceptors Cd and Hg. Crystals doped with these impurities have been used for infrared detector applications and the hole binding energies of the neutral species are well known. It would be interesting to explore the electronic and the real space structure of A(Cd,H) and A(Hg,H) if they can be formed. 

A lithium niobate crystal doped with Pr + ions is excited with light of wavelength 470 nm. Structured emission bands centered around 620 nm, 710 nm, 880 nm, and 1062 nm are observed. Using the Dieke diagram, identify the excited and terminal states responsible for the previous emission bands. 

In order to develop a phosphor emitting at about 285 nm, a crystal doped with... 

The analytical properties of the fluoride ion-selective electrode At present, practically only ISEs constructed from a LaFj single crystal doped with EuFj and with internal metal contacts are used (see p. 65). A microelectrode for 2iLd of sample has also been constructed [85]. The standard type of LaFj ISE... 

Undoped p-alumina demonstrates a maximum conductivity and minimum activation energy when the sodium excess is around 20 to 30 mole%. Thereafter, further increase in the sodium content causes the conductivity to decrease. By contrast, P-alumina crystals doped with have a much higher conductivity than do undoped crystals. Explain these observations. 

Taushanoff S, Le KV, Williams J, Twieg RJ, Sadashiva BK, Takezoe H, Jakli A (2010) Stable amorphous blue phase of bent-core nematic liquid crystals doped with a chiral material. J Mater Chem 20 5893-5898... 

Tuning of the pre-tilt angle at the interface was also demonstrated by doping commonly used polyimide alignment layers with POSS nanoparticles [339]. In addition, the fabrication of a tunable liquid crystal flat microlens was achieved by placing a drop of a nematic liquid crystal doped with POSS nanoparticles onto a substrate inducing planar alignment (local HAN mode) [340]. Simultaneously, Takatoh and co-workers extended this concept to a series of metal oxide... 

In comparison to nematic liquid crystals, examples of smectic liquid crystals doped with quasi-spherical nanoparticles became more elusive over the last few years. This is surprising especially considering recent work by Smalyukh et al., who found that nanoscale dispersion (based on /V-vinyl-2-pyrrolidone-capped gold nanoparticles with 14 nm diameter) in a thermotropic smectic liquid crystal (8CB) are potentially much more stable than dispersions of nanoparticles in nematics [367]. 

Haase and co-workers investigated electro-optic and dielectric properties of ferroelectric liquid crystals doped with chiral CNTs [495, 496]. The performance of the doped liquid crystal mixture was greatly affected even by a small concentration of CNTs. The experimental results were explained by two effects (1) the spontaneous polarization of the ferroelectric liquid crystal is screened by the 7t-electron system of the CNT and (2) the CNT 7i-electrons trap ionic impurities, resulting in a significant modification of the internal electric field within liquid crystal test cells. 

Vemavarapu, C., M. J. Mollan, andT. E. Needham. 2002. Crystal doping aided by rapid expansion of supercritical solutions APS Pharm Sci TedBi1-15. 

Fig. 2.10 Planar representation of a silicon crystal doped with P5+ giving rise to a Ps defect.

For n-type GaN crystals doped with Si or 0, from TABLE 1, we find a decrease in EM. It follows that valence control using donor dopants, Si and 0, is likely to prove extremely useful in fabricating high-conductivity n-type doped GaN crystals with stable ionic charge distributions. 

TABLE 2 The differences in the calculated Madelung energies between undoped, p-type GaN crystals doped with Be or Mg alone and p-type O- or Si-codoping GaN Be(Mg). The energy positions are measured relative to the Fermi level of each crystal. The second row contains AEM between undoped and p-type doped GaN. 

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