Papers by Keyword: Tungsten Nitride

Abstract: A rapid solvent-free melting route has been successfully developed for the synthesis of tungsten nitrides with lamellar and solid spherical nanostructures which have considerably different surface areas (106.4 m² g^-1 contrast to 8.3 m² g^-1) by the reaction of WCl6 and NaNH2 at 220 °C for 2-5 h directly, and it is found that the heat insulating property of reaction container plays important roles in the composition, phase, and morphologies of the nitrides. The products were analyzed by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS). Their thermal stability and surface area were measured by thermogravimetric analysis (TGA) and BET, respectively. Finally, the possible formation mechanism of tungsten nitrides with different morphologies was also investigated.

Abstract: The synthesis and deposition behavior of tungsten nitrides on a Si(400) or quartz plate were studied using a vertical hot-wall tube reactor. The preparation of the tungsten nitride by chemical vapor deposition (CVD) is predicted by the sticking probability of tungsten nitride by calculating the step coverage on the Si(400) engraved with a microtrench of different aspect ratios. The CVD deposition was performed at temperatures of 556–1063 K for deposition times up to 45 min in a gas mixture of WF6–NH3–H2 in Ar and at a total pressures of 5 and 13 Pa. From the XRD analysis, amorphous crystallites were observed at 556 and 673 K but β–W2N (111) was obtained at 790 K. The film thickness of the tungsten nitride linearly increased with the increasing deposition time at 673 and 790 K without any orientation despite the film thickness. The sticking probabilities, η, are 0.00044–0.00123 for Si(400) with different aspect ratios under the conditions of 5–13 Pa and 10–20 min.

Abstract: Tungsten oxynitride films (WOxNy) were deposited with a chemical composition in the range of 0 < x < 1 and 0 < y < 1. For the W-N system, the α-W, β-W, and β-W2N phases were identified according to the amount of nitrogen. In the W-O-N system the structure depended on the amount of oxygen. For an oxygen fraction, fO2 = CO/(CO+CN), smaller than 0.46 the β-W2N phase is evident, whereas above that value the structure became amorphous.