Dopant distribution, controlling

Imaging SIMS. Steeds et al. (1999) included this technique in their study of the distribution of boron introduced into diamond, where it is a well-established dopant that controls the electrical conductivity. SIMS was performed with a field-emission liquid gallium ion source interfaced to a magnetic sector mass spectrometer capable of about 0.1 pm spatial resolution. 

Control of Dopant Distribution into Core-Shell UCNPs 229... 

CONTROL OF DOPANT DISTRIBUTION INTO CORE-SHELL UCNPs... 

Control of Ln Dopant Distribution into Core—Shell UCNPs 233... 

In Bridgman-type crystal-growth configurations one possibility to control convection and therefore the shape of the solid/liquid interface, as well as the dopant distribution, is the so-called accelerated cmcible rotation technique (ACRT). This technique was developed by Scheel [56] and has been applied especially to the Bridgman growth of CdHgTe and CdZnTe crystals, e.g. [57, 58). 

The main drawbacks of solid-state techniques are that (i) the distribution of the dopant in the host lattice may not be even since the precursors are not mixed on the atomic scale, and (ii) particle growth cannot be easily controlled and so milling and sieving is necessary. 

One way to overcome the sample homogeneity problem has been to develop standards by ion implantation [80-83]. Here, the concentration and distribution of the dopants can be controlled more accurately, thereby forming standards with better homogeneity. However, the results with semiconductors, have been much more reliable than with ion-implanted metal standards [82, 83]. 

SIMS is a very surface-sensitive technique because the emitted particles originate from the uppermost one or two monolayers. The dimensions of the collision cascade are rather small and the particles are emitted within an area of a few nanometers diameter. Hence, SIMS can be used for microanalysis with very high lateral resolution (50 nm to 1 pm), provided such finely focused primary ion beams can be formed. Furthermore, SIMS is destructive in nature because particles are removed from the surface. This can be used to erode the solid in a controlled manner to obtain information on the in-depth distribution of elements.109 This dynamic SIMS mode is widely applied to analyze thin films, layer structures, and dopant profiles. To receive chemical information on the original undamaged surface, the primary ion dose density must be kept low enough (<1013 cm-2) to prevent a surface area from being hit more than once. This so-called static SIMS mode is used widely for the characterization of molecular surfaces (see Figure 3.10). 

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. 

Dopant atoms chemical impurities that are deliberately introduced into the semiconductor lattice to provide control over the conductivity and Fermi level of the solid Doping the introduction of specific chemical impurities into a semiconductor lattice to control the conductivity and the Fermi level of the semiconductor Effective density of states the number of electronic states within ikT of the edge of an energy band, where k is the Boltzmann constant and T is the temperature Energy bands a cluster of orbitals in which the individual molecular orbitals are packed closely together to form an almost continuous distribution of energy levels... 

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