Positron annihilation lifetime spectroscopy based on secondary electron emission from carbon foil

16th International Conference on Positron Annihilation

Ng, C.K.^1 ; Yang, B.^1 ; Fung, S.^1

Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong, Hong Kong^1

关键词: High-time resolution;    Positron annihilation lifetime spectroscopy;    Radial electric field;    Secondary electron emissions;    Secondary electrons;    Timing simulations;    Transmission geometries;    Variable-energy positron annihilation;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/443/1/012097/pdf
DOI  :  10.1088/1742-6596/443/1/012097

来源: IOP

【 摘 要 】

Using the emission of secondary electron (SE) from a thin carbon foil in transmission geometry guided by a strong radial electric field in the region between the foil and the sample under investigation, a new variable energy positron annihilation lifetime spectroscopy (PALS) system is being implemented. To this end, the SE emission from a carbon foil of 30nm thick has been investigated in transmission geometry. Considerable emission of SE from the foil with peak energy of about 5eV is observed. We have found that both the energy loss and dispersion of the positrons after transmission through the carbon foil are small enough for the proposed positron lifetime-depth profiling PALS system to be realised. These experimental results and the timing simulations of Cai et. al. [1] indicate that the proposed variable PALS based on secondary electrons generated by carbon foil have a high time resolution.