Kelvin Probe Force Microscopy Imaging of Plasticity in Hydrogenated Perovskite Nickelate Multilevel Neuromorphic Devices

• Published in: ACS nano Vol. 19; no. 7; pp. 6815 - 6825
• Main Authors: Dey, Tamal, Lai, Xinyuan, Manna, Sukriti, Patel, Karan, Patel, Ranjan Kumar, Bisht, Ravindra Singh, Zhou, Yue, Shah, Shaan, Andrei, Eva Y., Sankaranarayanan, Subramanian K. R. S., Kuzum, Duygu, Schuman, Catherine, Ramanathan, Shriram
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 25.02.2025
• Subjects: nickelates; memory; Kelvin probe force microscopy; neural networks; synaptic plasticity; imaging; neuromorphic computing
• ISSN: 1936-0851; 1936-086X; 1936-086X
• DOI: 10.1021/acsnano.4c11567

Ion drift in nanoscale electronically inhomogeneous semiconductors is among the most important mechanisms being studied for designing neuromorphic computing hardware. However, nondestructive imaging of the ion drift in operando devices directly responsible for multiresistance states and synaptic memory represents a formidable challenge. Here, we present Kelvin probe force microscopy imaging of hydrogen-doped perovskite nickelate device channels subject to high-speed electric field pulses to directly visualize proton distribution by monitoring surface potential changes spatially, which is also supported with finite element-based electric field distribution studies. First-principles calculations provide mechanistic insights into the origin of surface potential changes as a function of hydrogen donor doping that serves as the contrast mechanism. We demonstrate 128 (7-bit) nonvolatile conductance levels in such devices relevant to in-memory computing applications. The synaptic plasticity measurements are implemented in spiking neural networks and show promising results for classification (SciKit Learn’s Iris and Wine data sets) and control (OpenAI’s CartPole-v1 and BipedalWalker-v3) simulation tasks.