Enhanced Field-Effect Control of Single-Layer WS₂ Optical Features by hBN Full Encapsulation

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) van der Waals (vdW) semiconductors exhibit unique electrical and optical properties tunable via electric fields.
• Field-effect transistors (FETs) are commonly fabricated using 2D vdW materials.
• The field effect can modulate excitonic optical emission in 2D transition metal dichalcogenides.

Purpose of the Study:

• Investigate the field-effect control of optical and excitonic properties in monolayer tungsten disulfide (WS2).
• Compare the field-effect tunability in encapsulated and unencapsulated WS2 devices.
• Analyze the impact of hexagonal boron nitride (hBN) encapsulation on WS2 optical emission and device hysteresis.

Main Methods:

• Fabrication of planar single-layer WS2 devices using deterministic vdW material transfer.
• Contacting devices with gold electrodes and partially sandwiching with hBN flakes.
• Optical characterization of both hBN-encapsulated and unencapsulated WS2 regions.

Main Results:

• Encapsulation with hBN significantly enhances the tunability of WS2 photoluminescence.
• The optical emission was tuned from exciton-dominated to trion-dominated regimes.
• Full hBN encapsulation reduced spurious hysteretic effects in field-effect control.

Conclusions:

• Hexagonal boron nitride encapsulation is crucial for achieving a wider range of field-effect control over WS2 optical properties.
• This technique offers a pathway to minimize hysteresis in 2D vdW electronic and optoelectronic devices.
• The findings are relevant for developing advanced 2D semiconductor-based optoelectronic applications.