Titanium Nitride Diffusion Enables Visualization of Filamentary Switching in Ovonic Threshold Switching Selectors

Area of Science:

• Materials Science
• Electronics Engineering
• Nanotechnology

Background:

• Ovonic threshold switching (OTS) selectors are crucial for high-density memory and computing.
• Understanding their switching mechanisms is vital but challenging due to the amorphous nature of materials.

Purpose of the Study:

• To elucidate the switching mechanism in chalcogenide-based OTS devices.
• To provide direct structural evidence of conductive pathways.
• To optimize OTS device performance for memory applications.

Main Methods:

• Utilized four-dimensional scanning transmission electron microscopy (4D-STEM) with angstrom-beam electron diffraction.
• Employed titanium nitride (TiN) diffusion as a natural tracer.
• Introduced a carbon interfacial layer to control diffusion.

Main Results:

• Directly mapped continuous conductive pathways formed by TiN clusters within As₂Se₃.
• Confirmed filamentary switching behavior in OTS devices.
• Achieved an ultralow leakage current of 8 pA by controlling TiN diffusion with a carbon layer.

Conclusions:

• The study provides direct evidence for filamentary switching mechanisms in chalcogenide-based OTS devices.
• Controlling electrode material diffusion is key to reducing leakage current.
• Offers practical design strategies for highly reliable memory selectors.