WO3 oxide film formation on tungsten in O2/H2 discharges |
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Authors: | A E Gorodetsky R Kh Zalavutdinov V L Bukhovets L P Kazansky A P Zakharov |
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Institution: | 1. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow, Russia
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Abstract: | The features of tungsten oxidation in a flowing O2 or O2/H2 mixture glow discharge with a hollow cathode are investigated in the cathode, plasma, and afterglow regions at T = 300–350 K. The structure and composition of the samples are analyzed via reflection high-energy electron diffraction, reflection X-ray diffraction, electron probe microanalysis, and X-ray photoelectron spectroscopy. The results of analysis show that the metal surface is covered by a thin film (5–10 nm thick) of amorphous porous hydrated tungsten oxide (WO3) after its exposure to the discharge and storage in air. The study of the film composition using a time-of-flight mass spectrometer indicates that the WO3 film contains (WO3) n (n = 1–6) clusters and water molecules adsorbed in the pores. After exposure of the polycrystals to the O2/H2 discharge, the selective intense oxidation of individual grains is detected in the cathode region; the surrounding areas are subjected to weaker oxidation. The thicknesses of the WO3 films on neighbouring grains differ by more than tenfold. Such grains can be the source of tungsten dust in plasma installations. |
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