Transparent Conductive Two-Dimensional Titanium Carbide Epitaxial Thin Films.

Area of Science:

• Materials Science
• Nanotechnology
• Solid State Physics

Background:

• Two-dimensional (2D) materials research has surged since graphene's discovery.
• MXenes, a family of 2D transition metal carbides/carbonitrides, offer a unique combination of conductivity and hydrophilicity.
• Previous MXene forms (powders, flakes, solutions) limited large-scale applications.

Purpose of the Study:

• To develop a method for fabricating large-area (∼1 × 1 cm²) titanium carbide (Ti₃C₂) films.
• To characterize the structural, optical, and electrical properties of the fabricated Ti₃C₂ films.
• To explore the potential applications of these 2D MXene films in electronics and photonics.

Main Methods:

• Fabrication of epitaxial Ti₃AlC₂ films via sputtering.
• Selective etching of aluminum (Al) from Ti₃AlC₂ films using aqueous hydrofluoric acid (HF) or ammonium bifluoride (NH₄HF₂).
• Characterization of film thickness, light transmittance, electrical conductivity, and magnetoresistance.

Main Results:

• Successfully fabricated ∼1 × 1 cm² Ti₃C₂ films with a thickness of approximately 19 nm.
• NH₄HF₂-etched films exhibited high optical transparency (∼90% in visible-to-infrared range).
• Films demonstrated metallic conductivity down to ∼100 K, with resistivity increasing and negative magnetoresistance observed below this temperature, indicative of weak localization.

Conclusions:

• The developed etching technique enables the scalable production of high-quality 2D Ti₃C₂ MXene films.
• The observed properties suggest that these large-area MXene films are promising candidates for electronic, photonic, and sensing applications.
• This work significantly advances the potential for integrating MXenes into practical devices.