Photocarrier dynamics in monolayer phosphorene and bulk black phosphorus
Photocarrier dynamics in monolayer phosphorene and bulk black phosphorus
复制标题
单层磷烯和块状黑磷中的光载流子动力学
作者：
Zereshki Peymon;Wei Yaqing;Ceballos Frank;Bellus Matthew Z;Lane Samuel D;Pan Shudi;Long Run;Zhao Hui
本文报道了单层磷烯和块体黑磷中光生载流子动力学的理论和实验研究。单层磷烯和散装黑磷的样品制造的机械剥离，确定根据其反射对比度，并通过覆盖它们与六方氮化硼层的保护。利用超快泵浦-探测技术研究了这些样品中的光生载流子动力学。单层磷烯的光生载流子寿命约为700 ps，是体黑磷的9倍。这种趋势在我们的计算基础上的从头算非绝热分子动力学结合时域密度泛函理论在Kohn-Sham表示再现，可以归因于更小的带隙和更强的非绝热耦合在散装。瞬态吸收响应也被发现是依赖于相对于泵浦偏振，这是与先前报道的磷烯的各向异性吸收的样品取向。此外，在早期的探测延迟的差分反射信号的振荡分量中观察到的散装样品，并归因于层呼吸声子模式的能量约为1毫电子伏和约1.35 ps的衰减时间。这些结果为单层磷烯在光电子学中的应用提供了有价值的信息。
We report a combined theoretical and experimental study on photocarrier dynamics in monolayer phosphorene and bulk black phosphorus. Samples of monolayer phosphorene and bulk black phosphorus were fabricated by mechanical exfoliation, identified according to their reflective contrasts, and protected by covering them with hexagonal boron nitride layers. Photocarrier dynamics in these samples was studied by an ultrafast pump–probe technique. The photocarrier lifetime of monolayer phosphorene was found to be about 700 ps, which is about 9 times longer than that of bulk black phosphorus. This trend was reproduced in our calculations based on ab initio nonadiabatic molecular dynamics combined with time-domain density functional theory in the Kohn–Sham representation, and can be attributed to the smaller bandgap and stronger nonadiabatic coupling in bulk. The transient absorption response was also found to be dependent on the sample orientation with respect to the pump polarization, which is consistent with the previously reported anisotropic absorption of phosphorene. In addition, an oscillating component of the differential reflection signal at early probe delays was observed in the bulk sample and was attributed to the layer-breathing phonon mode with an energy of about 1 meV and a decay time of about 1.35 ps. These results provide valuable information for application of monolayer phosphorene in optoelectronics.