Fracture mechanism and temperature/size-dependent thermal conductivity in gallium selenide monolayer

TBT Tran and TH Fang and DQ Doan, VACUUM, 201, 111037 (2022).

DOI: 10.1016/j.vacuum.2022.111037

Gallium selenide monolayer (GSM) was recently proposed as a potential two-dimension material in electronic, spintronic, and optoelectronic applications. This work investigates the anisotropic mechanical properties and thermal conductivity of the GSM structure using molecular dynamics (MD) and non-equilibrium MD (NEMD) simulations, which are the key for designing nanodevices. First, we evaluate the GSM atomistic deformation mechanisms and mechanical properties influenced by tensile strain rate and temperature under uniaxial and biaxial tension. Second, impacts on thermal conductivity are investigated concerning modifications of temperature, model length and temperature differences between the heat source and heat sink. The results show that GSM exhibits excellent mechanical properties with sustaining a uniaxial tensile strain of 38.84% and 27.35% in the zigzag (Zz) and armchair (Ac) direction according to that is 31.47% for both directions of biaxial (Bi) tension at a temperature of 1 K. We found that the GSM has a weak- anisotropy in mechanical property with the Youngs modulus is around 66.77 GPa and 67.56 GPa under uniaxial tension in the Zz and Ac directions. Likewise, it reaches 80.52 in both Zz and Ac directions with biaxial tension. Besides, the temperature strongly impacts both mechanical properties and thermal conductivity of GSM, which have a steady reduction as raising the temperature. However, these parameters have a reasonably weak dependence on the tensile strain rate, except for the highest applied strain rate of 5 x 10(9) s(-1)with the highest YM of 62.77, 64.41, and 80.00 GPa for the Zz, Ac, and biaxial tension. We have obtained that effective thermal conductivity k gets the lowest value of 26.90 W/m.K and 35.37 W/m.K for Zz and Ac direction of a GSM size of (20 x 15) nm. These values are determined at an infinite length of approximately 62.50 W/m.K and 54.05 W/m.K in the two directions. Although thermal conductivities have minor fluctuations when changing temperature differences, the investigated results are correct, notwithstanding any temperature difference values between the two thermal baths.

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