Time of flight spectra of electrons emitted from graphite after positron annihilation

14th International Workshop on Slow Positron Beam Techniques & Applications

Gladen, R.W.^1 ; Chirayath, V.A.^1 ; Chrysler, M.D.^1 ; McDonald, A.D.^1 ; Fairchild, A.J.^1 ; Shastry, K.^1 ; Koymen, A.R.^1 ; Weiss, A.H.^1

Dept. of Physics, University of Texas at Arlington, Arlington

TX

76019, United States^1

关键词: Electron spectrum;    Highly oriented pyrolytic graphite;    Low energy beams;    Maximum intensities;    Secondary process;    Time of flight spectrum;    Time-of-flight spectrometer;    University of Texas;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/791/1/012031/pdf
DOI  :  10.1088/1742-6596/791/1/012031

来源: IOP

【 摘 要 】

Low energy (∼2 eV) positrons were deposited onto the surface of highly oriented pyrolytic graphite (HOPG) using a positron beam equipped with a time of flight (TOF) spectrometer. The energy of the electrons emitted as a result of various secondary processes due to positron annihilation was measured using the University of Texas at Arlington's (UTA) TOF spectrometer. The positron annihilation-induced electron spectra show the presence of a carbon KLL Auger peak at ∼263 eV. The use of a very low energy beam allowed us to observe a new feature not previously seen: a broad peak which reached to a maximum intensity at ∼4 eV and extended up to a maximum energy of ∼15 eV. The low energy nature of the peak was confirmed by the finding that the peak was eliminated when a tube in front of the sample was biased at -15 V. The determination that the electrons in the peak are leaving the surface with energies up to 7 times the incoming positron energy indicates that the electrons under the broad peak were emitted as a result of a positron annihilation related process.