Novel field emission devices for vacuum nanoelectronics and optoelectronic applications

There has been a recent surge of interest in nanostructured materials for vacuum nanoelectronic devices and optoelectronic applications. Specifically, the high electric fields surrounding a nanostructure can create highly nonlinear tunnelling currents across few-nanometer free-space gaps. Such nanostructures can be used for creating low-power, high-speed nonlinear electronic circuit elements for operation in harsh environments, or novel optoelectronic devices exhibiting petahertz-level bandwidths. While noble metals exhibit high field enhancement, especially in the optical regime due to their plasmonic behavior, they are prone to damage and performance degradation because of their low melting point. Refractory plasmonic materials are promising for applications in harsh environments due to their high bulk melting point. Titanium nitride is a refractory and CMOS-compatible alternative material for plasmonic applications. The tunability of its optical properties by adding Si and O2 dopants was recently demonstrated, enabling many applications. In this work, we simulated the optical response of titanium silicon oxynitride (TiSiON) bow-tie nanoantennas, highlighting their advantages and drawbacks with respect to noble metals and other materials. We also pointed out the influence of the geometry on their optical response. We successfully developed a reliable cleanroom etching procedure to fabricate bow-tie nanostructures arrays with sub-10-nm wide gaps and aspect ratio larger than 5. We performed electrical and optical testing on fabricated arrays. We obtained an electric current of 5 nA/tip with a bias voltage of 10 V in an array of about 2000 bow-tie nanostructures with an average gap size of 14 nm. From the same array, we obtained a photocurrent of 150 nA/tip using an incident laser with a power of 13 mW and an applied bias voltage of 5 V. We also demonstrated that TiSiON has not degraded with testing, when not electromigrated. In conclusion, we proved the suitability of titanium silicon oxynitride for vacuum nanoelectronics and optoelectronic applications. With further optimization, TiSiON could be a good candidate to replace the state-of-the-art materials and improve the performances of the devices in harsh environments.