Space Charge Expansion for Time-resolved Spin-Polarized Electron Spectroscopy

TL;DR

This study investigates how space charge effects influence time-resolved spin-polarized electron spectra in heterostructures, revealing pulse expansion phenomena that enable high polarization measurements exceeding 90%.

Contribution

It introduces an analysis of space charge pulse expansion in spin-polarized electron spectroscopy and compares heterostructures with different strain configurations.

Findings

Pulse profiles are modified by space charge expansion at currents above 10 nA.

Electrons with minimal sample transit time exhibit polarization above 90%.

Differences in pulse profiles are linked to variations in effective NEA values.

Abstract

Time resolved spin-polarized electron photoemission spectra are investigated as a function of excitation pulse energy for the heterostructures with a single strained layer and with a strained-well superlattice. At an average current exceeding 10 nA the emission pulse profiles are modified by the space charge pulse expansion during the electron transport to detector. The pulse expansion enables the separation of electrons that have spent minimum time in the sample. For the superlattice structure these electrons showed maximum polarization above 90 %. Variation in the pulse profiles for the two structures is interpreted as resulting from the difference in the effective NEA values.