Lithographic techniques for fabrication of spin injection and detection devices exploiting ferromagnetic semiconducting Gadolinium Nitride

This thesis will present a variety of methods for fabricating spin-injection and detection device based on the rare-earth nitrides as ferromagnetic electrodes and copper as a spin diffusion channel on Si/SiO2substrates. The fabrication of a spin injection device is shown using photolithographic methods in tandem with; Photomask based patterning, Ar-assisted ion milling, Direct laser writing, and Electron beam lithography. This is the first ever work that has used electron beam lithography for patterning rare-earth nitride devices with submicron features, as all previous works have used photolithography. The design, fabrication and testing of devices focuses on achieving high device yield, and reduction of device features. The best method for successfully patterning a rare-earth nitride-based spin injection device down to nm scale involves using electron-beam lithography, but film adhesion issues will have to be solved to produce devices ready for testing.

Devices were characterised and tested using XRD, SEM and a four terminal lateral non-local electrical measurement geometry. Electrical resistance of the various current paths in the device were measured, as well as attempts to measure a fully fabricated device using the four terminal lateral non-local experimental set up. A spin injection and detection device using GdN was fully fabricated and can be easily reproduced. However, the devices were found to be fragile and easily damaged during electrical measurements. Therefore, future work needs to focus on improving the robustness of the device.