Graphene passivation effect on copper cavity resonator preserves Q-factor

Area of Science:

• Microwave Engineering
• Materials Science
• Surface Science

Background:

• Estimating material surface conductivity is crucial for microwave device design.
• Traditional methods face challenges with losses from mechanical connections and surface contamination.
• Resonator-based techniques offer high sensitivity for surface property analysis.

Purpose of the Study:

• To develop and validate a resonator design for precise surface conductivity measurements.
• To investigate the impact of surface modification techniques on resonator performance.
• To enhance the sensitivity and stability of microwave resonators for material characterization.

Main Methods:

• Design and fabrication of a novel resonator with no mechanical connections.
• Experimental study of copper cavity resonator surface modification via annealing (H2/Ar, 1070 °C) and graphene coating (CVD).
• Measurement of intrinsic quality factor (Q) and frequency shifts before and after surface treatments.

Main Results:

• The developed resonator design minimizes losses, concentrating 60% of losses in the sample for high sensitivity.
• Annealing copper surfaces in H2/Ar significantly increases the resonator's quality factor due to reduced resistance and grain growth.
• Graphene coating stabilizes the quality factor by preventing oxidation and contamination, retaining benefits of annealing.

Conclusions:

• The proposed resonator design and surface modification techniques (annealing and graphene coating) effectively enhance and stabilize resonator quality factor.
• These methods are suitable for accurate estimation of material surface conductivity and thin film surface impedance in microwave devices.
• The findings contribute to the development of more sensitive and reliable microwave measurement tools.