Critical field of two-dimensional superconducting Sn_1-x/Si _x bimetallic composite cluster assembled films with energetic cluster impact deposition

Sn_1-x/Si_x cluster assembled films have been prepared by an energetic cluster impact deposition using a plasma-gas-condensation cluster beam deposition apparatus. Transmission electron microscope images indicated that individual clusters have composite morphologies, where Sn and Si were separated from each other. The superconducting critical magnetic fields, H_c, of Sn_1-x/Si_x cluster assembled films were measured and found to be much higher than the critical magnetic field of the bulk Sn. We estimated the H_c values by using a theory of the superconducting thin film. The estimated values are in good agreement with the experiments, indicating that the Sn_1-x/Si_x cluster assembled films can be regarded as a two-dimensional system although thickness, t, of Sn_1-x/Si_x cluster assembled films (t ≈ 1000 nm) is thicker than conventional superconducting thin film (t 100 nm).