Dielectric Regulation in Quasi-vdW Europium Oxysulfur Compounds by Compositional Engineering for 2D Electronics

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Next-generation electronics require precise control over dielectric properties in two-dimensional (2D) materials.
• Existing 2D materials often present trade-offs between dielectric constant and bandgap, limiting device performance.

Purpose of the Study:

• To synthesize and characterize novel 2D quasi-van der Waals (vdW) europium oxysulfur (Eu₂SOₓ) compounds.
• To investigate the composition-tunable dielectric properties of these new materials.
• To demonstrate the application of these compounds as gate dielectrics in 2D field-effect transistors (FETs).

Main Methods:

• Homodiffusive-controlled epitaxial growth was employed to synthesize hexagonal Eu₂SO₂ and tetragonal Eu₂SO₆ phases.
• Material characterization focused on dielectric properties (dielectric constant, bandgap) and device performance metrics.
• Ultrathin Eu₂SO₂ nanoplates were integrated with molybdenum disulfide (MoS₂) FETs via vdW forces.

Main Results:

• Two novel 2D Eu₂SOₓ phases, hexagonal Eu₂SO₂ (dielectric constant ≈30, bandgap ≈4.56 eV) and tetragonal Eu₂SO₆ (dielectric constant ≈20, bandgap ≈5.62 eV), were synthesized.
• Eu₂SO₂/MoS₂ FETs exhibited a near-ideal on/off ratio (≈10⁸), minimal hysteresis (≈5.3 mV), a low subthreshold slope (≈63.5 mV dec⁻¹), and ultralow leakage current (≈10⁻¹⁴ A).
• The study successfully demonstrated the ability to tune dielectric properties by controlling the composition of Eu₂SOₓ compounds.

Conclusions:

• Europium oxysulfur compounds offer a promising solution to the dielectric constant-bandgap trade-off in 2D materials.
• These novel materials are suitable for advanced gate dielectric applications in next-generation nanoelectronics.
• Composition engineering of rare-earth oxysulfur compounds can expand their utility in various electronic applications.