Tungsten nitrides

Tungsten nitride shows extreme hardness, high chemical stability and high electrical conductivity [172]. The compound is a promising candidate for diffusion barriers and gate electrodes in electronic devices [173-175]. This material has been prepared by the CVD of a mixture of tungsten hexachloride, NH3 and H2 at 500-900 °C [172], from a mixture of WF6/NH3/H2 at 450-650°C [176] and from the unimolecular precursor (t-BuN)2 V(NH-/-Bu)2 at 450-650°C ]177]. 

---

A Du Pont patent " reports that tungsten nitride preferably supported on alumina or titania is an active catalyst for amination by reaction of an alcohol with an amine in the presence of hydrogen. Examples are given of the amination of monoethanolamine by diethylenetriamine and amination of mon-oethanolamine by ethylenediamine. 

The reason indium nitride UFPs cannot grow by this method is probably the low decomposition temperature (620°C) of InN. The similar consideration can be done on tungsten nitride and molybdenum nitride. The phases of W2N and Mo2N are recognized in UFPs, but no WN and MoN phases are detected their decomposition temperature is about 80()°C. 

In order to study the chemical effects on the Auger peaks of tungsten carbides and nitrides by factor analysis, it was necessary to prepare model samples of tungsten nitrides and carbides where the chemical species of nitrogen, carbon and tungsten were separated. A sample where the different chemical species were mixed was also prepared. 

In addition to the reagents described, NC13 has been reported to generate trichloro-tungsten nitride 105 from the corresponding tungsten hexacarbonyl 104 (Eq. (39)). 

Reactive deposition has developed into a powerful technology over the last 30 years. It is historically interesting to note that in early studies, Soddy [388] found in 1907 that calcium vapour is highly reactive to most gases and that Langmuir [389] in 1913 investigated the formation of tungsten nitride by vapour-phase reaction of the elements. 

Terminal tungsten nitride complexes containing W N bonds have been reported to catalyze nitrile-alkyne cross-metathesis (NACM) by a mechanism that has parallels with the non-pairwise mechanism for olefin metathesis (A. M. Geyer, E. S. Weidner, J. B. Gary, R. L. Gdula, N. C. Kuhlmann, M. J. A. Johnson, B. D. Dunietz, J. W. Kampf, J. Am. Chem. Soc., 2008, 130, 8984.) When p-methoxybenzonitrile and 3-hexyne were mixed in the presence of catalyst candidate N=W(OC(Cp3)2Me)3(DME), two principal products attributable to metathesis were observed. 

S. D. Marcus and R. F. Foster, Characterization of low pressure chemically vapor-deposited tungsten nitride films. Thin Solid Films 1993, 236, 331 and 332. 

Kiefer B, Shieh SR, Duffy ThS, Sekine T (2005) Strength, elasticity, and equation of state of the nanocrystalUne cubic silicon nitride y-Si3N4 to 68 GPa. Phys Rev B 72 014102 Wang Z, Pischedda V, Saxena SK, Lazor P (2002) X-ray diffraction and Raman spectroscopic study of nanocrystalline CuO under pressures. Solid State Commun 121 275-279 Ma Y, Cui Q, Shen L, He Z (2007) X-ray diffraction study of nanocrystaUine tungsten nitride and tungsten to 31 GPa. J Appl Phys 102 013525... 

---