High-temperature conductance loss dominated defect level in h-BN: Experiments and first principles calculations

The dielectric properties of hexagonal boron nitride are investigated in detail. The permittivities hold extremely low values ranging from room temperature to 1500 ° C , however, the dielectric loss tangents increase rapidly above 1000 ° C . At 1500 ° C , the dielectric loss tangent is 20 times more than that at room temperature. The first principles calculations show that the boron vacancy ( V B ) that gives an acceptor energy level near the valence band presents the lowest ionization energy in the investigated defects, and the calculated V B ionization energy agrees with the experimental value. It indicates that the rapid increase in dielectric loss tangents at high temperature is contributed by electrical conductivity produced by V B ionization under thermal excitation.