Charge Carriers Localization Effect Revealed through Terahertz Spectroscopy of MXene: Ti₃C₂T_x

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• MXenes, particularly Ti3C2Tx, are promising materials for optical and electronic devices.
• Previous terahertz time-domain spectroscopy (THz-TDS) studies were limited by narrow frequency ranges, hindering a full understanding of MXene carrier transport.
• Understanding carrier transport mechanisms is crucial for optimizing MXene applications.

Purpose of the Study:

• To investigate the complex photoconductances of MXene (Ti3C2Tx) films with varying thicknesses using ultrabroadband THz-TDS (up to 15 THz).
• To elucidate the substrate-dependent nature of electronic localization in MXene films.
• To explore the impact of layer number on carrier transport properties and identify screening effects.

Main Methods:

• Utilized ultrabroadband terahertz time-domain spectroscopy (THz-TDS) up to 15 THz.
• Investigated complex photoconductances of MXene (Ti3C2Tx) films with different thicknesses.
• Employed optical pump THz probe spectroscopy (OPTP) to study photocarrier dynamics.

Main Results:

• Electronic localization in MXene films was found to be substrate-dependent.
• The degree of electronic localization decreased with an increasing number of MXene layers.
• Layer-independent photocarrier relaxations indicated a carrier heating-induced screening effect, attributed to high carrier density in Ti3C2Tx.

Conclusions:

• The study reveals crucial insights into carrier transport mechanisms in MXene films, particularly the role of substrate and layer number.
• The findings highlight the significance of carrier screening effects in Ti3C2Tx.
• These results provide a foundation for advancing MXene applications in optical and electronic devices.