Charge carrier mobilities in γ-graphynes: a computational approach.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• Graphynes are 2D carbon allotropes with tunable electronic properties and intrinsic band gaps, making them attractive for semiconductor applications.
• Accurate theoretical characterization, especially for electron-phonon coupling (EPC), is computationally intensive for graphynes.

Purpose of the Study:

• To develop an efficient and accurate computational approach for characterizing graphyne properties, focusing on EPC and transport.
• To investigate the structural, mechanical, electronic, and transport properties of graphyne and graphdiyne.

Main Methods:

• Employed the density functional tight binding (DFTB) method within the DFTBEPHY framework for efficient EPC and transport property calculations.
• Compared transport calculations using the constant relaxation-time approximation (CRTA) and self-energy relaxation-time approximation (SERTA).
• Utilized analytical models based on parabolic- and Kane-band approximations.

Main Results:

• Calculated SERTA relaxation times for graphyne: 0.63 ps (holes) and 1.69 ps (electrons).
• Calculated SERTA relaxation times for graphdiyne: 0.04 ps (holes) and 0.14 ps (electrons).
• Achieved hole mobilities in graphyne up to 10^3 cm^2 V^-1 s^-1 and electron mobilities up to 10^4 cm^2 V^-1 s^-1.
• Obtained mobility values for both charge carriers in graphdiyne on the order of 10^2 cm^2 V^-1 s^-1.
• Phonon-limited mobilities at room temperature for graphyne are between graphene and MoS2; for graphdiyne, they are comparable to MoS2.

Conclusions:

• The DFTB-based DFTBEPHY framework provides an efficient and accurate method for computing EPC and transport properties of graphynes.
• Graphyne exhibits promising charge transport characteristics, with electron mobilities potentially exceeding those of graphene.
• Graphdiyne shows mobilities comparable to MoS2, indicating its potential for specific semiconductor applications.