Giant and Tunable Out-of-Plane Spin Polarization of Topological Antimonene

Fabrication and Characterization of Silicon-Based Antimonene Thin Film via Electron Beam Evaporation

Antimonene has attracted much attention due to its excellent characteristics of high carrier mobility, thermoelectric properties and high stability. It has great application prospects in Q-switched lasers, laser protection and spintronics. At present, the epitaxy growth of antimonene mainly depends on molecular beam epitaxy. We have successfully prepared antimonene films on silicon, germanium/silicon substrates for the first time using electron beam evaporation coating and studied the effects of the deposition rate and substrate on the preparation of antimonene; film characterization was performed via confocal microprobe Raman spectroscopy, via X-ray diffraction and using a scanning electron microscope. Raman spectroscopy showed that different deposition rates can lead to the formation of different structures of antimonene, such as α phase and β phase. At the same time, it was found that the growth of antimonene is also affected by different substrates and ion beams.

Nonadiabatic Molecular Dynamics with Non-Condon Effect of Charge Carrier Dynamics

Nonradiative multiphonon transitions play a crucial role in understanding charge carrier dynamics. To capture the non-Condon effect in nonadiabatic molecular dynamics (NA-MD), we develop a simple and accurate method to calculate noncrossing and crossing k-point NA coupling in momentum space on an equal footing and implement it with a trajectory surface hopping algorithm. Multiple k-point MD trajectories can provide sufficient nonzero momentum multiphonons coupled to electrons, and the momentum conservation is maintained during nonvertical electron transition. The simulations of indirect bandgap transition in silicon and intra- and intervalley transitions in graphene show that incorporation of the non-Condon effect is needed to correctly depict these types of charge dynamics. In particular, a hidden process is responsible for the delayed nonradiative electron-hole recombination in silicon: the thermal-assisted rapid trapping of an excited electron at the conduction band minimum by a long-lived higher energy state through a nonvertical transition extends charge carrier lifetime, approaching 1 ns, which is about 1.5 times slower than the direct bandgap recombination. For graphene, intervalley scattering takes place within about 225 fs, which can occur only when the intravalley relaxation proceeds to about 50 fs to gain enough phonon momentum. The intra- and intervalley scattering constitute energy relaxation, which completes within sub-500 fs. All the simulated time scales are in excellent agreement with experiments. The study establishes the underlying mechanisms for a long-lived charge carrier in silicon and valley scattering in graphene and underscores the robustness of the non-Condon approximation NA-MD method, which is suitable for rigid, soft, and large defective systems.