Superconducting properties of sputtered Mo-C films with columnar microstructure

We have fabricated MoxC1-xthin film samples by sputtering, and have studied the dependence of superconducting critical temperatures, fields, and currents on composition and microstructure. For x in the range from 40-60%, the preferred nonequilibrium Mo-C Bl phase (with Tcup to 13K) grows in an oriented columnar structure, with column diameters of 100-1000Å. This is correlated with sharply enhanced perpendicular critical fields (with extrapolated values of Hc2(O) that can exceed 300kOe) together with a critical current density that may be as large as 10⁶A/cm². We also present data on artificial layered structures based on Mo-C, fabricated either by alternately sputtering Si layers or by pulsed gas injection of N2.