Crystalline defect

S. Metz, G. Kilian, G. Mainka, C. An-GELKORT, A. Pester, B. O. Kolbesen, Proc. -Electrochem. Soc. (1997) PV 97-22 (Crystalline Defects and Contamination Their Impact and Control in Device Manufacturing II) p. 458-467. 

The objective of this section is to show by means of specific examples how the various crystalline defects and structural features described in Section 20.4 can affect the form, location and kinetics of the corrosion of metals and alloys. 

The atomic bonds in a cylinder of material around dislocations are elastic-ally stretched dislocations, like other crystalline defects, are therefore high-energy regions. 

The deposition points on the lithium electrode are the points at which the protective film has a higher lithium-ion conductivity. One example of these deposition points are the pits on the lithium anode caused by discharge. Crystalline defects and the grain boundaries in lithium may also initiate deposition. 

After the fiber-like lithium has grown, lithium is still deposited on the lithium substrate that is not at the tip of the fiber-like lithium. If the deposition continues for a long time, the lithium electrode becomes covered with long, fiber-like lithium. In this situation, lithium-ion transport in the electrolyte to the lithium electrode surface is hindered by the fiber-like lithium. Then, lithium begins to be deposited on the tip and on kinks of the fiber-like lithium, where there are crystalline defects. The morphology of the deposited lithium is particle-like or amorphous. As there are many kinks, the current density of the lithium deposition becomes very low. This low current density may create particle-like, rather than fiber-like, lithium. Thus the morphology of the lithium as a whole becomes mushroom-like [31]. 

Titanium-tungsten is an intermetal lie, composed mostly of tungsten. It is an excellent barrier if it is stuffed, that is, with nitrogen added into the crystalline defects. It prevents diffusion of silicon into aluminum up to 500°C. It is deposited mostly by sputtering. 

The two extremes of ordering in solids are perfect crystals with complete regularity and amorphous solids that have little symmetry. Most solid materials are crystalline but contain defects. Crystalline defects can profoundly alter the properties of a solid material, often in ways that have usefial applications. Doped semiconductors, described in Section 10-, are solids into which impurity defects are introduced deliberately in order to modify electrical conductivity. Gemstones are crystals containing impurities that give them their color. Sapphires and rubies are imperfect crystals of colorless AI2 O3, red. 

Intrinsic Defects The simplest crystalline defects involve single or pairs of atoms or ions and are therefore known as point defects. Two main types of point defect have been identified Schottky defects and Frenkel defects. A Schottky defect consists of a pair of vacant sites a cation vacancy and an anion vacancy. A Schottky defect is... 

Lebedeva NP, Rodes A, Feliu JM, Koper MTM, van Santen RA. 2002b. Role of crystalline defects in electrocatalysis CO adsorption and oxidation on stepped platinum electrodes as studied by in situ infrared spectroscopy. J Phys Chem B 106 9863-9872. 

In a crystalline medium, the parametric gain (2) T2 is propor-tionnal to d2 Ip n-3 and the oscillation condition r2A2>aA where a is the signal residual absorption (dramatically increased by any crystalline defect), d the efficient phase-matched nonlinear susceptibility, n an average refractive index, Ip the pump intensity (limited by the optical damage threshold) and A the effective interaction length (also limited by any source of crystalline disorientation). 

The achievement of the corresponding monocrystals of sufficient optical and crystalline quality is made possible only after very thorough purification. Chemical impurities are known to disturb the crystal lattice through the occurence of twins, veils dislocations, rounding-off of faces ultimately quenching further growth. Any crystalline defect dramatically increases the residual absorption coefficient and lowers the optical damage threshold. 

Using solid-state physics and physical metallurgy concepts, advanced non-destructive electronic tools can be developed to rapidly characterize material properties. Non-destructive tools operate at the electronic level, therefore assessing the electronic structure of the material and any perturbations in the structure due to crystallinity, defects, microstructural phases and their features, manufacturing and processing, and service-induced strains.1 Electronic, magnetic, and elastic properties have all been correlated to fundamental properties of materials.2 5 An analysis of the relationship of physics to properties can be found in Olson et al.1... 

The fabrication process of vanadium oxide (VO2) has also been studied using RBS/C. Since optieal and electrical properties of VO2 are dramatically changed at 68°C due to phase transition, VO2 is regarded as one of the candidates for thermally activated electronic or optical switching devices for optieal fibers or sensors. To obtain the desired properties, the development of the fabrication process for very thin films, without crystalline defects on various substrates, is required. Single-crystalline VO2 thin films on (0001) plane of a sapphire substrate have been synthesized by a laser ablation method. The quality of VO2 was examined by X-ray diffraction and RBS/C method. The eleetrieal resistanee and the optical transmittance of the VO2 film were measured under inereasing and deereasing temperatures. At a temperature of 68 °C, an abrupt transition of resistanee from metal to... 

Preferential diffusion along crystalline defects can give rise to a profile resembling that shown in Fig. 5(d). 

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