Plasma-Assisted Atomic Layer Deposition of IrO₂ for Neuroelectronics

Area of Science:

• Neuroscience
• Materials Science
• Electrochemistry

Background:

• Microelectrode arrays are crucial for in vitro and in vivo neuron action potential recording and stimulation.
• Iridium oxide (IrO2) is a biocompatible material with superior charge injection capabilities compared to noble metals.
• Atomic layer deposition (ALD) offers conformal growth suitable for 3D nanoelectrode arrays.

Purpose of the Study:

• To develop a novel plasma-assisted ALD (PA-ALD) process for growing nanocrystalline rutile IrO2 at low temperatures (150 °C).
• To comprehensively characterize the morphological, structural, physical, chemical, and electrochemical properties of the synthesized IrO2 thin films.
• To evaluate the electrochemical performance of PA-ALD grown IrO2 for potential neuroelectronic applications.

Main Methods:

• Plasma-assisted atomic layer deposition (PA-ALD) was employed to grow IrO2 thin films on PtSi substrates at 150 °C.
• Extensive characterization included morphological, structural, physical, chemical, and electrochemical analyses.
• Electrochemical measurements focused on charge injection capacity, charge storage capacity, and double-layer capacitance.

Main Results:

• Nanocrystalline rutile IrO2 was successfully synthesized using the novel PA-ALD process.
• The IrO2 films exhibited excellent electrochemical properties, including a double-layer capacitance (C) exceeding 300 µF·cm⁻².
• A high charge injection capacity of 0.22 ± 0.01 mC·cm⁻² was achieved for a 1.0 cm² electrode.

Conclusions:

• The PA-ALD process provides a viable method for producing high-performance IrO2 films at low temperatures.
• The characterized electrochemical properties confirm IrO2 grown by PA-ALD as a promising material for advanced neuroelectronic devices.
• This research contributes to the development of next-generation neural interfaces for stimulation and recording.