EPJ Web Conf.
Volume 255, 2021EOS Annual Meeting (EOSAM 2021)
|Number of page(s)||4|
|Section||Topical Meeting (TOM) 13- Ultrafast Optical Technologies and Applications|
|Published online||18 November 2021|
Dynamical imaging of local photovoltage at semiconductor surface by photo-assisted ultrafast scanning electron microscopy
1 Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci, 32, 20133 Milano, Italy
2 Institute for Photonics and Nanotechnologies (IFN)—National Research Council (CNR), Piazza L. da Vinci, 32, 20133 Milano, Italy
3 CNST@PoliMi, Istituto Italiano di Tecnologia (IIT), Via Giovanni Pascoli 70/3, Milano, Italy
4 LNESS-Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
Published online: 18 November 2021
Photo-assisted Ultrafast Scanning Electron Microscopy (USEM) maps the dynamics of surface photovoltages and local electric fields in semiconducting samples. Photovoltages and their gradients close to surface affect the emission yield and the detection efficiency of secondary electrons (SE), leading to photoexcited SE 2D patterns. In this work, we present a method to characterize the evolution of the patterns up to ultrafast regime. These results reveal the role of surface states in affecting the external field dynamics at picoseconds. Moreover, we show that tiny changes in surface preparation express deeply different photoexcited voltage signals. We investigate the relation between the surface chemistry of Si and photo-induced SE contrast.
© The Authors, published by EDP Sciences, 2021
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