Ag-B thin films prepared by magnetron sputtering

The discovery of the new superconductor MgB₂ with critical temperature of T_c = 39 K stimulated great activity in search for materials with higher T_c. Theoretical works predicted the possibility of obtaining such superconducting materials in other borides also, in particular in AgB₂. It was predicted in these works that diborides of metals having the AlB₂ type structure, among them AgB₂, may have superconductivity with a T_C higher than 39 K. In an early very short report the lattice parameters of AgB₂ were evaluated in a synthesized specimen. However, no other indication exists that AgB₂ was ever produced. We report the preliminary results of our attempts to prepare AgB₂ films. Thin films of Ag-B were produced by magnetron cosputtering in Ar ambient from two separate targets that of B and Ag on Si (100) substrates. The specimens were subjected to X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photo spectroscopy (XPS), Auger analysis and optical microscope (OM) investigations. Resistivity measurements in a wide temperature range were measured. No superconductivity was yet observed in the range -10 -200 K on the basis of resistivity measurements. Preliminary results indicate that AgB₂ might be an unstable phase.