Thickness dependence of Jc (0) in MgB2 films

• A serial of MgB2 superconducting films from 10 nm to 8 µm have been prepared.
• Tc and Jc (5 K, 0 T) of films are high.
• Jc (5 K, 0 T) reaches its maximum 2.3 × 108 A cm−2 for 100 nm films.
• The relationship between thickness and Jc has been discussed in detail.

MgB2 superconducting films, whose thicknesses range from 10 nm to 8 µm, have been fabricated on SiC substrates by hybrid physical–chemical vapor deposition (HPCVD) method. It is the first time that the Tc and the Jc of MgB2 films are studied on such a large scale. It is found that with the increasing of thickness, Tc elevates first and then keeps roughly stable except for some slight fluctuations, while Jc (5 K, 0 T) experiences a sharp increase followed by a relatively slow fall. The maximum Jc (5 K, 0 T) = 2.3 × 108 A cm−2 is obtained for 100 nm films, which is the experimental evidence for preparing high-quality MgB2 films by HPCVD method. Thus, this work may provide guidance on choosing the suitable thickness for applications. Meanwhile, the films prepared by us cover ultrathin films, thin films and thick films, so the study on them will bring a comprehensive understanding of MgB2 films.