Femtosecond time-resolved spectroscopic photoemission electron microscopy for probing ultrafast carrier dynamics in heterojunctions

Abstract

The fast developing semiconductor industry is pushing to shrink and speed up transistors. This trend requires us to understand carrier dynamics in semiconductor heterojunctions with both high spatial and temporal resolutions. Recently, we have successfully set up a time-resolved photoemission electron microscopy (TR-PEEM), which integrates the spectroscopic technique to measure electron densities at specific energy levels in space. This instrument provides us an unprecedented access to the evolution of electrons in terms of spatial location, time resolution, and energy, representing a new type of 4D spectro-microscopy. Here in this work, we present measurements of semiconductor performance with a time resolution of 184 fs, electron kinetic energy resolution of 150 meV, and spatial resolution of about 150 nm or better. We obtained time-resolved micro-area photoelectron spectra and energy-resolved TR-PEEM images on the Pb island on Si(111). These experimental results suggest that this instrument has the potential to be a powerful tool for investigating the carrier dynamics in various heterojunctions, which will deepen our understanding of semiconductor properties in the submicron/nanometer spatial scales and ultrafast time scales.

Endotaxial Intergrowth of Copper Telluride in GeTe-Rich Germanium Antimony Tellurides Leads to High Thermoelectric Performance

“…Photoemission electron microscopy (PEEM) was conducted at the XPPEM end station of beamline 09 U (Dreamline) in the Shanghai Synchrotron Radiation Facility (SSRF), which is equipped for spectroscopic photoemission and low energy electron microscopy (SPELEEM-III, Elmitec GmbH) . A 10 × 10 × 1 mm 3 sample of Cu 2 Ge 11 Sb 2 Te 15 was measured in an ultrahigh vacuum (UHV) chamber with a base pressure of ∼1 × 10 –10 Torr.…”

“…photoemission and low energy electron microscopy (SPELEEM-III, Elmitec GmbH). 81 A 10 × 10 × 1 mm 3 sample of Cu 2 Ge 11 Sb 2 Te 15 was measured in an ultrahigh vacuum (UHV) chamber with a base pressure of ∼1 × 10 −10 Torr. The sample was heated by the radiation from a tungsten filament underneath, and the temperature was increased by 2−3 K/min.…”

“…and low energy electron microscopy (SPELEEM-III, Elmitec GmbH) 81. A 10 × 10 × 1 mm 3 sample of Cu 2 Ge 11 Sb 2 Te 15…”

MAXPEEM: a spectromicroscopy beamline at MAX IV laboratory

“…At NSLS II (Reininger et al, 2012), which hosts a similar instrument, the main difference is the spot size (50 mm) and grazing incidence illumination. At Shanghai Synchrotron Radiation Facility (Xue et al, 2014), an aberration-corrected photoemission electron microscope (AC-PEEM) is used for time-resolved photoelectron microscopy (Li et al, 2019). There are also two non-commercial aberration-corrected PEEM instruments: one is SMART type at BESSY II [a complete version with LEEM function and a dedicated Omega-type energy filter (Schmidt et al, 1998)] and the other one is PEEM3 at the Advanced Light Source (beamline 11.0.1.1).…”