| Summary: | 碩士 === 國立臺灣大學 === 應用力學研究所 === 101 === Hexagonal boron-nitride (h-BN) nanosheets are promising materials for the next generation electronic devices. In this work, we systematically investigated the dependencies of h-BN thermal conductivities on nanoribbon edge chiral angles, vacancy concentration by carrying out a series of non-equilibrium molecular dynamics (NEMD) simulations.
Our simulation results indicate the thermal conductivities of BN nanoribbons have similar edge chiral angle dependencies with graphene nanoribbons, and longer BN nanoribbons yield higher thermal conductivities. Furthermore, the present study also reveals that thermal conductivity of BN nanosheets undergoes significant drops due to phonon scattering induced by vacancies. We also found that large vacancies are energetically more favorable than small vacancies, implying the aggregation of small vacancies into vacancy clusters, thereby minimizing thermal conductivity drops of BN nanosheets.
We also construct the dislocations and grain boundaries based on the geometries calculated by first principle method. In these results, we have learned that 4|8dislocation pairs can exists more energetically favorable than 5|7 dislocation pair due its unpolar property. With this statement, we started our study by constructing more grain boundaries spread in a wide misorientation angles. Our results have showed an contradiction to dislocation theorem which dislocations would reduce the mechanical strength several orders from pristine structure. But it is actually performing that mechanical strength can’t decrease over an order of the strength, and even increased when dislocation density become higher.
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