Role of a capping layer on the crystalline structure of Sn thin films grown at cryogenic temperatures on InSb substrates
Résumé
Sn thin films were deposited at -193°C in ultra high vacuum on InSb(110) substrates. Cryogenic cooling ensured controllable crystallinity and homogeneous thickness of thin films below15 nm. We employed different in-situ capping strategies immediately after Sn deposition to minimize likelihood of dewetting of the thin films. X-ray diffraction show how the Sn crystalline structure is influenced by the different cappings. The film is predominantly in the cubic Sn phase alpha-Sn, is epitaxial on InSb and presents very low mosaicity. However, we identified a correlation between alumina capping and the abundance of the tetragonal Sn phase (beta-Sn). Heating by the alumina e-beam source is a potential reason for the partial crystalline phase transition in the Sn layer. The presence of the beta-Sn phase caused the superconducting behavior of the films by percolation effect. Finally, this work showed that ultra-thin films of Sn on InSb substrates can be produced controllably, with perspectives for quantum computing platforms.
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