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MgB2 thin films fabrication and structuring

Chiara Portesi 2Eugenio Monticone 2Valeria Dellarocca 1Renato S. Gonnelli 1

1. Dipartimento di Fisica, Politecnico di Torino, Italy, corso Duca degli Abruzzi, 24, Torino 10129, Italy
2. Istituto Elettrotecnico Nazionale "Galileo Ferraris", Italy (IEN), Strada delle Cacce, 91, Torino 10135, Italy


Since the discovery of its superconducting properties, magnesium diboride has generated a great interest because of its simple structure, relatively high critical temperature and pronounced two-gap nature. These properties make this superconductor good for many potential applications.
In this work, we present the results obtained in the fabrication, characterization and structuring of MgB2 thin film grown by so-called in situ method. This technique consisted in two steps: the first one was the co-deposition of B and Mg by means of e-gun and resistive heater respectively. During the deposition .the substrate was held at temperature of 280C.The second step was the annealing of the as-grown films in the deposition chamber at 500C in inert atmosphere.
Using this method, we obtained MgB2 thin films with rather good electrical properties and smooth and homogeneous surfaces. The analysis of the morphological and structural properties has been performed by means of AFM and XRD respectively. The critical temperature was about 32 -35 degrees and we always observed very sharp transitions; the roughness of the samples was ranging between 10 and 20 nm (if evaluated on 5 mm2 areas), and it was strongly dependent on the films thickness. The films were polycrystalline, with a columnar growth of the grains and in the best samples we observed a partial orientation along the c-axis.
The samples were structured using standard photolithographic process followed by chemical wet etching or by dry etching. For the chemical etching, we experimented different acid solutions and the best results have been obtained using HCl solution (0.05%),in which the sample was dipped for a few second.. By ion milling, we realized well defined 5 microns wide strips with very sharp edges.


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Presentation: poster at E-MRS Fall Meeting 2004, Symposium E, by Chiara Portesi
See On-line Journal of E-MRS Fall Meeting 2004

Submitted: 2004-04-30 17:33
Revised:   2009-06-08 12:55