Making electrical contacts to nanowires with a thick oxide coating

Abstract

Techniques are presented for making ohmic contacts to nanowires with a thickoxide coating. Although experiments were carried out on Bi nanowires, thetechniques described in this paper are generally applicable to other nanowiresystems. Metal electrodes are patterned to individual Bi nanowires using electronbeam lithography. Imaging the chemical reaction on the atomic scale with in situhigh-resolution transmission electron microscopy shows that annealing in H2or NH3 can reduce the nanowires’ oxide coating completely. The hightemperatures required for this annealing, however, are not compatible with thelithographic techniques. Low-resistance ohmic contacts to individual bismuthnanowires are achieved using a focused ion beam (FIB) to first sputteraway the oxide layer and then deposit Pt contacts. By combining electronbeam lithography and FIB techniques, ohmic contacts stable from 2 to400 K are successfully made to the nanowires. A method for preventingthe burnout of nanowires from electrostatic discharge is also developed.