Effects of Al2O3 capping layers on the thermal properties of thin black phosphorus

We investigate the thermal properties of thin black phosphorus (BP) with Al2O3 capping layer using the temperature-dependent and polarized-laser power-dependent Raman spectroscopy. Compared to the BP samples without Al2O3 capping layer, the Al2O3 passivation layer significantly improves the thermal stability of BP by reducing the thermal coefficients of the A(g)(1), B-2g, and A(g)(2) Raman modes from -0.0082, -0.0142, and -0.0145 cm(-1)/K to -0.0046, -0.0074, and -0.0088 cm(-1)/K, respectively, which are attributed to the compressive strain and strong Al-P and O-P bonds. Meanwhile, the thermal conductivity reaches to about 45.4 and 54.4 W/mK along the armchair and zigzag directions, greatly larger than those of the BP films without Al2O3 24.1 and 39.0 W/mK, respectively, owing to the large thermal conductivity of Al2O3 and the interface charges between Al2O3 and BP. Overall, this work will contribute to improve the BP-based device performances and extend the BP applications profoundly. Published by AIP Publishing.