Ultra-thin film NbN depositions for HEB heterodyne mixer on Si-substrates
Paper in proceeding, 2013

The key of improving hot-electron bolometer (HEB) mixer performance lies inevitably in the quality of ultra-thin NbN films itself. This work presents a thorough investigation of crucial process parameters of NbN films deposited by means of reactive DC-sputtering on Si-substrates at elevated temperatures up to 750°C. The polycrystalline NbN films with thickness of 4 to 10nm were characterized by DC resistivity measurements, ellipsometry and high resolution transmission electron microscopy (HRTEM) in order to confirm thickness and film structure. Since the macroscopic properties such as critical temperature, thickness as well as the transition width to the superconducting state are directly linked to HEB mixer noise temperature and IF bandwidth, a set of experiments were conducted to enhance aforementioned properties. We considered deposition temperature, RF biasing, nitrogen and argon partial and total pressure during deposition as major process variable parameters. Careful optimization of the deposition conditions allowed setting up a process resulting in high-quality NbN ultra-thin films with thickness of 5.5nm exhibiting Tc of 10.5K. Moreover, the transition width could be kept as low as 1.4K. The produced films were stored at ambient conditions and re-characterized over a period of 4 month without measurable degradation.

Author

Sascha Krause

Chalmers, Earth and Space Sciences, Advanced Receiver Development

Vincent Desmaris

Chalmers, Earth and Space Sciences, Advanced Receiver Development

Alexey Pavolotskiy

Chalmers, Earth and Space Sciences, Advanced Receiver Development

Denis Meledin

Chalmers, Earth and Space Sciences, Advanced Receiver Development

Victor Belitsky

Chalmers, Earth and Space Sciences, Advanced Receiver Development

E. Pippel

Proceedings of the 24th International Symposium on Space Terahertz Technology

Areas of Advance

Information and Communication Technology

Nanoscience and Nanotechnology

Subject Categories

Nano Technology

Other Electrical Engineering, Electronic Engineering, Information Engineering

More information

Created

10/7/2017