Solution-Processed NiPS₃ Thin Films from Liquid Exfoliated Inks with Long-Lived Spin-Entangled Excitons

Area of Science:

• Condensed Matter Physics
• Materials Science
• Opto-spintronics

Background:

• Antiferromagnetic materials offer THz spin dynamics and zero net magnetization, ideal for opto-spintronics.
• Layered van der Waals (vdW) antiferromagnets exhibit unique low-dimensional excitonic properties and complex spin structures.
• Scalable fabrication of high-quality, large-area vdW 2D crystal thin films remains a significant challenge.

Purpose of the Study:

• To develop a scalable method for fabricating centimeter-scale, continuous thin films of the vdW 2D antiferromagnetic material NiPS₃.
• To characterize the structural properties and control layer thickness of the fabricated NiPS₃ films.
• To investigate the opto-spintronic properties, including exciton dynamics and spin-light coupling, of the NiPS₃ films.

Main Methods:

• Liquid phase exfoliation (LPE) was employed to create a crystal ink of NiPS₃.
• Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used for statistical characterization of film properties.
• Ultrafast optical spectroscopy at cryogenic temperatures was utilized to probe photoexcited exciton dynamics.

Main Results:

• Centimeter-scale, continuous thin films of NiPS₃ were successfully fabricated using the ink-based LPE method.
• AFM and SEM analyses provided control over lateral size and layer number.
• Spectroscopic studies revealed nanosecond lifetimes for spin-entangled Zhang-Rice multiplet excitons and ultranarrow emission line widths, indicating high opto-spintronic quality despite film disorder.

Conclusions:

• The study demonstrates a scalable and effective method for producing high-quality NiPS₃ thin films.
• This scalable fabrication is crucial for the practical application of 2D antiferromagnets in spintronic and nanoscale memory devices.
• The findings pave the way for further exploration of complex spin-light coupled states in vdW antiferromagnets.