Comparative study of Ni nanowires patterned by electron-beam lithography and fabricated by lift-off and dry etching techniques

Abstract

Using e-beam lithography techniques we have patterned Ni wire widths down to less than 100 nm. The patterning techniques were utilized either to fabricate nanodeposition masks for further direct deposition of Ni and subsequent liftoff or to deposit Nb wire structures used for Ar ion-mill etch masks on top of Ni thin films. The resulting Ni nanowire structures showed strong differences in transport as well as differing morphologies measured by atomic force microscopy (AFM) and scanning electron microscopy. In the case of fabricating nanodeposition masks, direct deposition of Ni was performed by magnetron sputtering, thermal evaporation, and e-beam evaporation. In the resulting nanowires, e-beam evaporated wires show the best residual resistance and magnetoresistance (MR) characteristics. AFM results showed the nanowires produced by evaporation to have granular structure. The nanowires fabricated by dry etching surpassed all nanowires fabricated by direct deposition and liftoff in both residual resistances and MR characteristics. In terms of longitudinal MR response, all nanowires displayed changes from saturation values, which indicated the formation of domain walls during magnetic reversal.