All-Oxide ITO/HZO/WO_x Ferroelectric Tunnel Junctions with Oxygen-Engineered Interfaces for Highly Endurable...

Area of Science:

• Materials Science
• Solid State Physics
• Computer Engineering

Background:

• Ferroelectric tunnel junctions (FTJs) are key for neuromorphic computing due to their compact structure and multilevel conductance.
• Existing FTJ synapses often require complex multilayer stacks, hindering scalability and device integration.
• Developing simpler FTJ structures with stable interfacial transport is essential for advancing neuromorphic hardware.

Purpose of the Study:

• To demonstrate a structurally simple metal-ferroelectric-metal (MFM) FTJ synapse.
• To engineer the interface and electrode properties for stable switching without additional layers.
• To achieve reliable analog weight modulation for neuromorphic applications.

Main Methods:

• Fabrication of an ITO/Hf0.5Zr0.5O2/WOx stack.
• Tuning the oxygen stoichiometry of the WOx bottom electrode to create a trap-rich interface.
• Utilizing an ITO top electrode to optimize electric field distribution.
• Characterization of device performance, including resistance ratio, endurance, and conductance states.

Main Results:

• Demonstrated a structurally simple MFM FTJ (ITO/Hf0.5Zr0.5O2/WOx) without additional insertion layers.
• Achieved stable switching via polarization-modulated trap-assisted tunneling by tuning WOx stoichiometry.
• The optimized FTJ showed a resistance ratio of ~100, endurance >10^8 cycles, and 64 conductance states.
• Exhibited stable spike-dependent plasticity and analog weight modulation suitable for neuromorphic operation.

Conclusions:

• Simple MFM FTJ synapses with engineered interfaces offer a scalable solution for neuromorphic and in-memory computing.
• The demonstrated device achieves high performance metrics and reliable analog behavior.
• Neural network simulations using experimental data achieved 91.5% accuracy on the MNIST dataset, validating the device's potential.