TY - JOUR
T1 - Formation of N2O gas bubbles in anodic films on NbNx alloys
AU - Habazaki, H.
AU - Matsuo, T.
AU - Konno, H.
AU - Shimizu, K.
AU - Nagata, S.
AU - Takayama, K.
AU - Oda, Y.
AU - Skeldon, P.
AU - Thompson, G. E.
N1 - Funding Information:
Thanks are due to Mr Y. Uchida of Horiba Ltd, Tokyo, Japan for the provision of time on Jobin-Yvon RF5000 GDOES instrument. A part of this work was carried out under the Visiting Researcher's Programme of the Laboratory for Advanced Materials, Institute for Materials Research, Tohoku University. The present work was supported in part by the Grant-in-Aid for Scientific Research (C) No. 13650770 from the Japan Society for Promotion of Science.
Copyright:
Copyright 2004 Elsevier Science B.V., Amsterdam. All rights reserved.
PY - 2003/5/1
Y1 - 2003/5/1
N2 - Sputter-deposited niobium, and Nb90N10, Nb83N17 and Nb60N40 alloys, have been anodized at 50 A m-2 in 0.1 mol dm-3 ammonium pentaborate electrolyte at 293 K and resultant amorphous anodic films have been characterized by transmission electron microscopy, glow discharge optical emission spectroscopy, Rutherford backscattering spectrometry and Fourier-transform, infra-red spectroscopy. Except for the Nb60N40 alloy, which shows a breakdown at approximately 60 V, the deposited layers reveal a linear voltage increase to more than 150 V, with the rate decreasing with the niobium content. Additionally, anodic films, with flat and parallel metal/film and film/electrolyte interfaces, are formed on the specimens with the formation ratio decreasing with increasing nitrogen content in the deposited films. Nitrogen is incorporated into the inner ∼70-75% of the film thickness as N2O molecules, forming fine bubbles, with typical sizes up to 10 nm, in a Nb2O5-based matrix material. The remaining 25-30% of the film comprises a layer of Nb2O5 with the outer regions containing boron species derived from the electrolyte. Release of high pressure N2O gas is associated with the relatively low breakdown voltage for the Nb60N40 alloy of highest nitrogen content. The two-layered nature of the anodic films arises from the film growth mechanism that involves outward migration of niobium species and inward migration of oxygen species; in contrast nitrogen species are immobile due either to the relatively high energy of the N-O bond or to their presence in bubbles.
AB - Sputter-deposited niobium, and Nb90N10, Nb83N17 and Nb60N40 alloys, have been anodized at 50 A m-2 in 0.1 mol dm-3 ammonium pentaborate electrolyte at 293 K and resultant amorphous anodic films have been characterized by transmission electron microscopy, glow discharge optical emission spectroscopy, Rutherford backscattering spectrometry and Fourier-transform, infra-red spectroscopy. Except for the Nb60N40 alloy, which shows a breakdown at approximately 60 V, the deposited layers reveal a linear voltage increase to more than 150 V, with the rate decreasing with the niobium content. Additionally, anodic films, with flat and parallel metal/film and film/electrolyte interfaces, are formed on the specimens with the formation ratio decreasing with increasing nitrogen content in the deposited films. Nitrogen is incorporated into the inner ∼70-75% of the film thickness as N2O molecules, forming fine bubbles, with typical sizes up to 10 nm, in a Nb2O5-based matrix material. The remaining 25-30% of the film comprises a layer of Nb2O5 with the outer regions containing boron species derived from the electrolyte. Release of high pressure N2O gas is associated with the relatively low breakdown voltage for the Nb60N40 alloy of highest nitrogen content. The two-layered nature of the anodic films arises from the film growth mechanism that involves outward migration of niobium species and inward migration of oxygen species; in contrast nitrogen species are immobile due either to the relatively high energy of the N-O bond or to their presence in bubbles.
KW - Anodizing
KW - Ionic transport
KW - NO bubbles
KW - NbN alloys
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U2 - 10.1016/S0040-6090(03)00039-7
DO - 10.1016/S0040-6090(03)00039-7
M3 - Article
AN - SCOPUS:0038636448
VL - 429
SP - 159
EP - 166
JO - Thin Solid Films
JF - Thin Solid Films
SN - 0040-6090
IS - 1-2
ER -