In our laboratory we successfully produced thin films on Al 2O3 by sputtering a target, which is made of a mixture of MgB2 (commercial powder) and Mg, and went post-annealing process under different conditions. However, the films were not axial oriented and their superconductivity was not as great as MgB2 powders. We study the B and Mg K-edge absorption spectra and find followings: 1. The sputtered film (before ex situ annealing treatment) contains small amount of B 2O3 due to residual oxygen in the vacuum chamber, and unknown Mg compound. No signal of MgO is observed. 2. Under annealing temperature at 900°C, B2O3 is reduced to B by reacting with Mg and MgO is formed. No superconductivity was found. 3. Under annealing temperature at 600° ∼ 700°C, the Tc increases from 11.5 K to 25.5 K. The chemical shift of the pre-edge of the Mg K-absorption edge is greater as compared with that of MgB2 powder (Tc = 39 K). The Mg K-absorption spectrum indicates that the sample contains some amount of MgO.
|Number of pages||9|
|Journal||Chinese Journal of Physics|
|Issue number||4 II|
|Publication status||Published - 2004 Aug 1|
ASJC Scopus subject areas
- Physics and Astronomy(all)