Oxidation kinetics for thin rare-earth metal films

Publisher Website
Google Scholar
Abstract
We measured the oxidation rates of thin samarium, gadolinium, ytterbium, and yttrium films at room temperature in air by a simple optical transmission technique to help understand how to produce flat 100 nm or so thick films on 150-nm freestanding polymer substrates for use as x-ray lasers. The validity of the method is established with aluminum, whose oxide layer reaches a limiting thickness of about 5 nm within 1 h. The oxidation kinetics of different rare earths follow different rate laws. Ytterbium and gadolinium are best described by an inverse logarithmic rate law, yttrium by a direct logarithmic rate law, and samarium by a parabolic rate law. After 2 months, the oxide thicknesses of Y, Yb, Gd, and Sm are about 5, 9, 15, and 17 nm, respectively. Only Sm continues to oxidize rapidly, reaching 35 nm in 6.5 months. Spectroscopic results on Eu and Gd are consistent with previous results that the oxidized layer on the rare earths is usually a carbonated hydroxide. The results of our measurements are compared to those from initial oxidation studies by surface analysis techniques and high-temperature gravimetric studies.

This publication has 0 references indexed in Scilit: