The electrical resistivity of epitaxially deposited chromium films

We studied the electrical resistance and crystal structure of epitaxial chromium (Cr) films. The lattice constant of the Cr films is larger than that of the bulk Cr because the sample and the substrate MgO have different lattice constants. An chromium oxide layer having a thickness of 1 nm was found on all films from the result of X-ray reflectivity measurements. Although there is sample dependence in electric resistance of Cr films, it is remarkable that a zero resistance was observed for one film of 50 nm thick. TC is obtained to be 3.2 K, which is about twice the previous reports. The large upper critical field is obtained to be HC2 = 13 kOe, and it suggests that Cr may belongs to a type II superconductor.