Improvement of Reliability by Using Fluorine Doped Tin Oxide Electrode for Ta2O5 Based Transparent Resistive Switching Memory Devices

Purpose: Fluorine doped tin oxide (FTO) bottom electrode for Ta2O5 based RRAM was studied to apply for transparent resistive switching memory devices owing to its superior transparency, good conductivity and chemical stability.
Methods: ITO/Ta2O5/FTO (ITF) and ITO/Ta2O5/Pt (ITP) devices were fabricated on glass and Si substrate, respectively. UV-visible (UV-VIS) spectroscopy was used to examine transparency of the ITF device and its band gap energy was determined by conventional Tauc plot. Electrical properties, such as electroforming and voltage-induced RS characteristics were measured and compared.
Results: The device with an FTO bottom electrode showed good transparency (>80%), low forming voltage (~-2.5V), and reliable bipolar RS behavior. Whereas, the one with Pt electrode showed both bipolar and unipolar RS behaviors unstably with large forming voltage (~-6.5V).
Conclusion: Transparent and conducting FTO can successfully realize a transparent RRAM device. It is concluded that FTO electrode may form a stable interface with Ta2O5 switching layer and plays as oxygen ion reservoir to supply oxygen vacancies, which eventually facilitates a stable operation of RRAM device.