Positron Induced Electron Emission from Graphite

TL;DR

This study measures and analyzes positron-induced electron spectra from graphite, revealing mechanisms like Auger processes and positron sticking at low energies, using time-of-flight spectrometry with variable positron energies.

Contribution

It provides detailed measurements of PIES from graphite at various energies and clarifies the dominant mechanisms at low incident energies, advancing understanding of positron interactions with carbon materials.

Findings

PIES spectra show contributions from PAES, AMPS, and secondary electrons.

At energies ≤3.5 eV, spectra are explained by PAES and positron sticking.

The study enhances understanding of positron interactions with graphite.

Abstract

In this paper, we present and analyze measurements of the positron induced electron spectra (PIES) from highly oriented pyrolytic graphite (HOPG). The spectra were obtained using a time of flight spectrometer attached to a variable energy positron beam. In the first measurements presented, the system was configured to obtain high resolution data from the annihilation induced KVV Auger transition of carbon. In the second set of data presented, PIES spectra were obtained for 3 different positron beam energies (1.25 eV, 3.5 eV and 4.5 eV). The resulting time of flight (ToF)-PIES exhibit contributions arising from either positron annihilation induced Auger processes (PAES), Auger mediated positron sticking (AMPS), or secondary electron emission. Our analysis indicates that for incident positron energies 3.5 eV and less, the ToF-PIES can be accounted for considering only two mechanisms: positron annihilation induced Auger processes or positron sticking.