Transport properties of (Hg,M)-12(n-1)n (M=Re,Mo; n=2,3) superconducting thin films
We have successfully fabricated 200-500 nm thick highly c-axis oriented (Hg,Re)-1223 and (Hg,M)-1212 (M=Re,Mo) thin films on SrTiO/sub 3/(100) substrates by using HgO/M-Ba-Ca-Cu-O multilayer precursor films prepared by pulsed laser deposition. Their electrical transport properties in magnetic fields less than 7 T are investigated using 5-50 /spl mu/m wide bridges patterned by means of electron-beam lithography and ion milling without using water. The (Hg,Re)-1223 film exhibits a T/sub c/(zero) of 127.5 K and a J/sub c/ value at 77 K of 1.5 and 0.2/spl times/10/sup 6/ A/cm/sup 2/ in a self-field and 1 T field, respectively. Higher J/sub c/ values below 100 K are observed for (Hg,M)-1212 (M=Re,Mo) films with better crystallinity and surface morphology than the 1223 film in spite of their lower T/sub c/ (zero) of 115-122 K. The (Hg,Re)-1212 film exhibits the highest J/sub c/ values of 5, 1.5, and 0.4/spl times/10/sup 6/ A/cm/sup 2/ at 77 and 100 K in a self-field and at 77 K in 1 T field, respectively. The irreversibility field above 77 K evaluated from the resistive transitions of these films is found to be substantially higher than those for undoped Hg-1212 and Tl-1223 thin films.