RESUMEN
The spatiotemporal evolution of photogenerated charge carriers on surfaces and at interfaces of photoactive materials is an important issue for understanding fundamental physical processes in optoelectronic devices and advanced materials. Conventional optical probe-based microscopes that provide indirect information about the dynamic behavior of photogenerated carriers are inherently limited by their poor spatial resolution and large penetration depth. Herein, we develop an ultrafast scanning electron microscope (USEM) with a planar emitter. The photoelectrons per pulse in this USEM can be two orders of magnitude higher than that of a tip emitter, allowing the capture of high-resolution spatiotemporal images. We used the contrast change of the USEM to examine the dynamic nature of surface carriers in an InGaAs/InP avalanche photodiode (APD) after femtosecond laser excitation. It was observed that the photogenerated carriers showed notable longitudinal drift, lateral diffusion, and carrier recombination associated with the presence of photovoltaic potential at the surface. This work demonstrates an in situ multiphysics USEM platform with the capability to stroboscopically record carrier dynamics in space and time.
RESUMEN
Correction for 'Ultrafast switching to zero field topological spin textures in ferrimagnetic TbFeCo films' by Kaixin Zhu et al., Nanoscale, 2024, 16, 3133-3143, https://doi.org/10.1039/D3NR04529C.
RESUMEN
The capability of femtosecond (fs) laser pulses to manipulate topological spin textures on a very short time scale is sparking considerable interest. This article presents the creation of high density zero field topological spin textures by fs laser excitation in ferrimagnetic TbFeCo amorphous films. The topological spin textures are demonstrated to emerge under fs laser pulse excitation through a unique ultrafast nucleation mechanism, rather than thermal effects. Notably, large intrinsic uniaxial anisotropy could substitute the external magnetic field for the creation and stabilization of topological spin textures, which is further verified by the corresponding micromagnetic simulation. The ultrafast switching between topological trivial and nontrivial magnetic states is realized at an optimum magnitude of magnetic field and laser fluence. Our results would broaden the options to generate zero-field topological spin textures from versatile magnetic states and provides a new perspective for ultrafast switching of 0/1 magnetic states in spintronic devices.