Raman spectroscopy of 2D MoS₂ on Ti₃C₂ MXene: the substrate effect

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Molybdenum disulfide (MoS₂) is a layered material with unique electronic and optical properties.
• Titanium carbide (Ti₃C₂) MXene is a 2D material with high electrical conductivity.
• Understanding substrate interactions is crucial for optimizing 2D material device performance.

Purpose of the Study:

• To investigate the substrate effect of Ti₃C₂ MXene on the lattice vibrational modes of MoS₂.
• To elucidate the mechanisms behind the observed spectral shifts in MoS₂.
• To assess the influence of Ti₃C₂ MXene on MoS₂ across different layer numbers.

Main Methods:

• Raman spectroscopy was employed to analyze MoS₂ samples on Ti₃C₂ MXene substrates.
• Spectral analysis focused on fingerprint peaks, particularly the E¹_2g and A_1g modes.
• Experiments were conducted to evaluate laser power-dependent effects.

Main Results:

• Redshifts were observed in the Raman fingerprint peaks of MoS₂ when supported by Ti₃C₂ MXene.
• The in-plane E¹_2g mode shift was attributed to strain induced by the substrate.
• The out-of-plane A_1g mode softening was linked to electron doping from the Ti₃C₂ MXene.
• Substrate modulation effects were confirmed for monolayer, few-layer, and bulk MoS₂.
• Laser-induced shifts were detected even at low excitation power.

Conclusions:

• Ti₃C₂ MXene significantly influences MoS₂ vibrational properties through strain and electron doping.
• The substrate effect is present across various MoS₂ thicknesses.
• Careful consideration of laser power is essential for accurate interpretation of substrate effects in Raman spectroscopy of 2D materials.