In this work, we investigate the thermal and electrical properties ofoxygen-functionalized M2CO2 (M = Ti, Zr, Hf) MXenes using first-principlescalculations. Hf2CO2 is found to exhibit a thermal conductivity better thanMoS2 and phosphorene. The room temperature thermal conductivity along thearmchair direction is determined to be 86.25-131.2 Wm-1K-1 with a flake lengthof 5-100 um, and the corresponding value in the zigzag direction isapproximately 42% of that in the armchair direction. Other important thermalproperties of M2CO2 are also considered, including their specific heat andthermal expansion coefficients. The theoretical room temperature thermalexpansion coefficient of Hf2CO2 is 6.094x10-6 K-1, which is lower than that ofmost metals. Moreover, Hf2CO2 is determined to be a semiconductor with a bandgap of 1.657 eV and to have high and anisotropic carrier mobility. At roomtemperature, the Hf2CO2 hole mobility in the armchair direction (in the zigzagdirection) is determined to be as high as 13.5x103 cm2V-1s-1 (17.6x103cm2V-1s-1), which is comparable to that of phosphorene. Broader utilization ofHf2CO2 as a material for nanoelectronics is likely because of its moderate bandgap, satisfactory thermal conductivity, low thermal expansion coefficient, andexcellent carrier mobility. The corresponding thermal and electrical propertiesof Ti2CO2 and Zr2CO2 are also provided here for comparison. Notably, Ti2CO2presents relatively low thermal conductivity and much higher carrier mobilitythan Hf2CO2, which is an indication that Ti2CO2 may be used as an efficientthermoelectric material.
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