Ultrafast electron energy-dependent delocalization dynamics in germanium selenide

Zhesheng Chen,Chaofeng Gao,Luca Perfetti,Marino Marsi,Yingchun Cheng,Evangelos Papalazarou,Hao Zhang,Heqi Xiong,Jean-Pascal Rueff

doi:10.1038/s42005-021-00635-y

Abstract

Ultrafast scattering process of high-energy carriers plays a key role in the performance of electronics and optoelectronics, and have been studied in several semiconductors. Core-hole clock spectroscopy is a unique technique for providing ultrafast charge transfer information with sub-femtosecond timescale. Here we demonstrate that germanium selenide (GeSe) semiconductor exhibits electronic states-dependent charge delocalization time by resonant photo exciting the core electrons to different final states using hard-x-ray photoemission spectroscopy. Thanks to the experiment geometry and the different orbital polarizations in the conduction band, the delocalization time of electron in high energy electronic state probed from Se 1s is ~470 as, which is three times longer than the delocalization time of electrons located in lower energy electronic state probed from Ge 1s. Our demonstration in GeSe offers an opportunity to precisely distinguish the energy-dependent dynamics in layered semiconductor, and will pave the way to design the ultrafast devices in the future.

Highlights

Ultrafast scattering process of high-energy carriers plays a key role in the performance of electronics and optoelectronics, and have been studied in several semiconductors
Ultrafast electron dynamics in semiconductors play a key role in the performance of electronics and optoelectronics, and it can be directly observed by pump-probe spectroscopies[1,2,3], such as time-resolved photoemission spectroscopy
To the best of our knowledge, most of the previous work are focused on the carrier dynamics in fixed unoccupied states by resonant x-ray excitation, and it is still unclear the carrier dynamics behavior between different unoccupied states mainly due to the difficulty of finding a suitable system, which is very important for carrier dissipation and transport properties in electronic and optoelectronic devices

Summary

Introduction

Ultrafast scattering process of high-energy carriers plays a key role in the performance of electronics and optoelectronics, and have been studied in several semiconductors. We demonstrate that germanium selenide (GeSe) semiconductor exhibits electronic states-dependent charge delocalization time by resonant photo exciting the core electrons to different final states using hard-x-ray photoemission spectroscopy. The core–hole clock (CHC) spectroscopy has provided dynamics information as fast as tens of attoseconds[6,7,8,9,10,11], appearing as an ultrafast, complementary approach to pumpprobe spectroscopy This method uses an intrinsic timescale due to the core–hole lifetime of a specific atomic level, which allows us to elucidate electron–electron correlation effects and their role in excited electron dynamics. The state-dependent dynamics revealed in this study provides a unique handle to fine tune the ultrafast response of materials, offering an opportunity to design high performance ultrafast optoelectronic devices

Methods

Results

Conclusion