Processing effects on microstructure in Er and ErD sub(2) thin-films

• Published in: Journal of nuclear materials 2010-08, Vol.403 (1-3), p.191-197
• Main Authors: Parish, Chad M, Snow, Clark S, Kammler, Daniel R, Brewer, Luke N
• Format: Article
• Language: English
• ISSN: 0022-3115
• DOI: 10.1016/j.jnucmat.2010.06.026

Erbium metal thin-films have been deposited on molybdenum-on-silicon substrates and then converted to erbium dideuteride (ErD sub(2)). Here, we study the effects of deposition temperature ([asymptotic to]300 or 723 K) and deposition rate (1 or 20 nm/s) upon the initial Er metal microstructure and subsequent ErD sub(2) microstructure. We find that low deposition temperature and low deposition rate lead to small Er metal grain sizes, and high deposition temperature and deposition rate led to larger Er metal grain sizes, consistent with published models of metal thin-film growth. ErD sub(2) grain sizes are strongly influenced by the prior-metal grain size, with small metal grains leading to large ErD sub(2) grains. A novel sample preparation technique for electron backscatter diffraction of air-sensitive ErD sub(2) was developed, and allowed the quantitative measurement of ErD sub(2) grain size and crystallographic texture. Finer-grained ErD sub(2) showed a strong (1 1 1) fiber texture, whereas larger grained ErD sub(2) had only weak texture. We hypothesize that this inverse correlation may arise from improved hydrogen diffusion kinetics in the more defective fine-grained metal structure or due to improved nucleation in the textured large-grain Er.