Research - nickel nanowires
This research case study examines nickel oxide as it has attracted attention as a resistive switching material, however as yet, little investigation has been performed on resistive switching characteristics of nickel nanowires.
The first step in this process was controlled annealing of nickel nanowires to characterise void formation in the nanowires. The wires were annealed in atmosphere at 450ºC and clear void formation was visible.
The wires were then electrically characterised to assess switching properties. To accomplish electrical characterisation electron beam lithography was performed using a Zeiss SUPRA FESEM with a Raith Elphy attachment.
Image on the right shows nickel nanowires after ambient annealing.
Electrical characterisation could be performed after contacting using a combination of UV and electron beam lithography.
Pathways where there are no voids exhibited resistive switching, however, even in the case of voids being located in the channel, resistive switching occurred. These voids should be electrically insulating.
TEM was used to assess the nature of the material in the void. If an amorphous material was present insulating characteristics are expected, however if a crystalline material is present then a conducting characteristic is expected.
TEM images were obtained using an FEI TITAN,the amorphous nature of the void in the nanowire were confirmed using this method, however not all voids exhibited an amorphous nature.
The image on the right displays a different nanowire, zooming in on the void we can see some crystallinity, a further zoom in, we can clearly see a crystalline material. This goes some way to explaining why the electrical measurements across voids exhibited a non insulating characteristic.
Image on the right shows void area exhibiting crystalline nature.