  In a latest experimental advance, graphene-like and insulating BeO monolayer
was successfully grown over silver surface by molecular beam epitaxy (ACS Nano
15(2021), 2497). Inspired by this accomplishment, in this work we conduct
first-principles based simulations to explore the electronic, mechanical
properties and thermal conductivity of graphene-like BeO, MgO and CaO
monolayers. The considered nanosheets are found to show desirable thermal and
dynamical stability. BeO monolayer is found to show remarkably high elastic
modulus and tensile strength of 408 and 53.3 GPa, respectively. The electronic
band gap of BeO, MgO and CaO monolayers are predicted to be 6.72, 4.79, and
3.80 eV, respectively, using the HSE06 functional. On the basis of iterative
solutions of the Boltzmann transport equation, the room temperature lattice
thermal conductivity of BeO, MgO and CaO monolayers are predicted to be 385, 64
and 15 W/mK, respectively. Our results reveal substantial decline in the
electronic band gap, mechanical strength and thermal conductivity by increasing
the weight of metal atoms. This work highlights outstandingly high thermal
conductivity, carrier mobility and mechanical strength of insulating BeO
nanosheets and suggest them as promising candidates to design strong and
insulating components with high thermal conductivities.
