Nitrides crystal growth

The other method for nitride crystal growth is based on sublimation. Naoi et al [7] reported the RC for GaN crystals (of size up to 0.8 mm x 3 mm) grown by this technique. The measured FWHMs were... 

Grzegory I, Jun J, Bockowski M, Krukowski S, Wroblewski M, Lucznik B and Porowski S 1995 lll-V nitrides-thermodynamics and crystal growth at high N2 pressure J. Phys. Chem. Solids 56 639... 

Fischer R. A, Devi A (2000), Precursor Chemistry for OMVPE of group-13 nitrides. Recent Research and Developments in Crystal Growth 2, 61-82... 

The rapid development of solid state physics and technology during the last fifteen years has resulted in intensive studies of the application of plasma to thin film preparation and crystal growth The subjects included the use of the well known sputtering technique, chemical vapour deposition ( CVD ) of the solid in the plasma, as well as the direct oxidation and nitridation of solid surfaces by the plasma. The latter process, called plasma anodization 10, has found application in the preparation of thin oxide films of metals and semiconductors. One interesting use of this technique is the fabrication of complementary MOS devices11. Thin films of oxides, nitrides and organic polymers can also be prepared by plasma CVD. 

It is not always possible to obtain a low-porosity body by pressureless sintering , i.e. by sintering at atmospheric pressure. For example, difficulties are experienced with silicon nitride and silicon carbide. More commonly it may prove difficult to combine the complete elimination of porosity with the maintenance of small crystal size. These problems can usually by overcome by hot-pressing, i.e. sintering under pressure between punches in a die, as shown in Fig. 8.9. The pressure now provides the major part of the driving force eliminating porosity and the temperature can be kept at a level at which crystal growth is minimized. 

Metallic carbides, nitrides, and oxides are used industrially in many applications their physical properties are also of intrinsic interest. This section pinpoints various preparative techniques and reviews methods of crystal growth for this group of compounds. More detailed discussion is found in the reviews cited and in the references therein. The discussion is confined to binary compounds, M Xi, (M is a cation X = C, N, or O a and b are simple integers) that display metallic properties the very numerous ternaries MoMcXj, (M, M being different cations) cannot be described in this brief presentation. 

The methods for growth of single crystals of metallic carbides are like those for crystalline metallic nitrides however, carbide crystals significantly larger than nitride crystals can be grown. The following techniques are in common use. 

Past reviews of nitride crystal chemistry [2, 3] described cation coordination and some aspects of crystal growth techniques. More recent developments suggest that it is now timely to take a more in-depth review of known structures and to examine their crystal chemistry. 

I. Akasaki and H. Amano, Crystal growth and conductivity control of group III nitride semiconductors and their application to short wavelength light emitters, Jpn J. Appl. Phys. Pt 1 36, 5393-5408 (1997). 

The synthesis of diamond and cubic boron nitride has strongly motivated improvements in the development of high-pressure equipment and increased the interest in these materials, which have exceptional properties. Single crystals are required for optical and electronic applications. Consequently, specific crystal-growth processes have been set up under very high-pressure conditions. The principle is similar to that described, at lower pressures, for the preparation of single crystals of a-Si02. 

W. P. Chai, Y. S. Gu, M. Li, Z. H. Mai, Q. Z. Li, L. Yuan, and S. J. Pang, Orientation influence of cubic boron nitride crystal facets on the epitaxial growth of diamond film by microwave plasma chemical vapor deposition, J. Cryst. Growth, 135(3-... 

All precursors are amorphous up to calcination temperatures of around 600°C. At higher temperatures, in most cases powders with extremely small crystallite sizes of around 20-40 nm are formed (Fig. 7). A further increase in calcination temperature promotes crystal growth. With aluminum nitride, a white powder with a low oxygen and carbon content is obtained [97]. Other main group element precursors exhibit fairly different behaviors Mg and Ca precursors yield metal cyanamide [99]. Calcination of the transition element precursors (Fig. 8) results in the formation of nitrides, carbonitrides, or carbides. For the titanium-containing precursors, TiN/TiC solid solutions can be obtained [96] the quantity of carbon strongly depends on the calcination atmosphere applied (argon, 31 wt% ammonia, 5.1 wt%). 

The morphological pattern of the products of silicon vapor combustion in gaseous nitrogen at condensation synthesis with skeleton crystal formation as well as denchite growth of silicon nitride crystals in melted metal salts proves the existence of the nonequilibrium mechanism of structure formation in the case of SHS. The mechanism appears to be the basis of the conception of nanodispersed particle formation under the combustion mode [28]. 

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