High Performance Metal Oxide Field-Effect Transistors with a Reverse Offset Printed Cu Source/Drain Electrode

Area of Science:

• Materials Science
• Electrical Engineering
• Nanotechnology

Background:

• Developing low-cost, scalable fabrication methods for conductive films is crucial for advanced electronics.
• Solution-processable semiconductors offer potential for flexible and printed electronics.

Purpose of the Study:

• To investigate the properties of copper films fabricated using reverse offset printing.
• To optimize annealing conditions for improved film quality and electrical performance.
• To evaluate the use of printed copper as electrodes in solution-processed field-effect transistors.

Main Methods:

• Copper films prepared via nonvacuum, photolithography-free reverse offset printing.
• Annealing studies conducted at various temperatures (up to 400 °C) in a nitrogen atmosphere.
• Characterization of film properties including mechanical, morphological, structural, and chemical analysis.
• Fabrication and testing of zinc tin oxide field-effect transistors (FETs) using printed copper electrodes.

Main Results:

• Annealing promoted Ostwald ripening, grain growth, and coalescence in printed copper films.
• Increased annealing temperature reduced impurities (oxygen, hydrogen, carbon) and enhanced electrical conductivity to ~6.2 μΩ·cm at 400 °C.
• Zinc tin oxide FETs with printed copper electrodes achieved a field-effect mobility of 2.6 cm²/Vs, a threshold voltage of 7.0 V, and an on/off ratio of 2 × 10⁵.

Conclusions:

• Reverse offset printing is a viable method for fabricating high-conductivity copper films.
• Optimized annealing significantly improves the electrical properties of printed copper.
• Printed copper electrodes are suitable for high-performance, solution-processed zinc tin oxide transistors.