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Evidence for In-Plane Electrical Polarization in 3R-β'-In2Se3 Thin Films Grown by Molecular Beam Epitaxy.
Derrick Shao Heng Liu1, Sebastian Calderon2, Leonard Jacques3
1Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
ACS Applied Materials & Interfaces
|June 4, 2025
Summary
Researchers explored the ferroelectric potential of β-In2Se3 thin films grown by molecular beam epitaxy. While structural analysis indicated promising ferroelectric phases, electrical switching tests did not confirm ferroelectricity, revealing anisotropic transport instead.
Area of Science:
- Materials Science
- Solid State Physics
- Thin Film Growth
Background:
- Indium selenide (In2Se3) is a semiconductor material investigated for its potential ferroelectric properties.
- The 3R polytype, specifically 3R-β'-In2Se3, is of interest due to theoretical predictions of switchable polarization.
Purpose of the Study:
- To grow β-In2Se3 thin films using molecular beam epitaxy (MBE).
- To characterize the structural and morphological properties of the films.
- To investigate the ferroelectric properties and switchable polarization of 3R-β'-In2Se3.
Main Methods:
- Molecular beam epitaxy (MBE) for thin film growth.
- Atomic force microscopy (AFM), X-ray diffraction (XRD), and Raman spectroscopy for structural and morphological analysis.
- Scanning transmission electron microscopy (STEM) and second harmonic generation (SHG) for detailed structural and optical characterization.
- Electrical transport measurements to probe polarization switching and anisotropic responses.
Main Results:
- Smooth β-In2Se3 thin films were successfully grown on Si(111) and Al2O3(0001) substrates under optimized conditions (Se/In flux ratio and temperature).
- STEM confirmed the 3R polytype, with minor 2H polytype disorder at the interface.
- Evidence for in-plane Se atom displacements, characteristic of 3R-β'-In2Se3, was observed in films on Al2O3(0001) but not on Si(111).
- Electrical polarization switching attempts were unsuccessful in demonstrating ferroelectricity.
- Electrical transport measurements revealed anisotropic responses and hysteresis, attributed to charge trapping.
Conclusions:
- MBE is a viable technique for growing β-In2Se3 thin films with controlled polytypes.
- While structural features suggestive of ferroelectricity were observed, conclusive evidence for switchable polarization was not obtained.
- The material exhibits anisotropic electrical transport properties, indicating complex charge dynamics rather than simple ferroelectricity.
