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Contenuto archiviato il 2022-12-23

Design and research of new type photoemitters of polarized electrons

Obiettivo



Sources of polarized electrons based on photoelectronemission are very powerful tools in solid state physics, in atomic physics, in elementary particle physics, as well as in nuclear physics. In all these fields the number of investigations using beams of polarized electrons is increasing rapidly, because new insights into fundamental spin-dependent interactions between electrons and matter are possible.

Up to now photocathodes made from bulk GaAs or its relatives have been used primarily for producing sources of polarized electrons. This material allows the emission of electrons spinpolarized to a degree of 50% only. New cathodes based on strained layers of III-V-semiconductors or on III-V-superlattice structures give polarization values above the 50% limit. First promising results are reported in the literature by American and Japanese groups.

The goal of this project is the development of new types of photoemitters of polarized electrons. Encouraging data have already been produced. Investigations of strained GaAs- and GaAsP-cathodes produced by the loffe Institute in St. Petersburg reveal a spinpolarization of emitted electrons up to 88%, while the second Russian group in Novosibirsk has developed InGaAsP-cathodes that produce photoelectrons with a degree of polarization of 55%, so far at a high quantum efficiency.

In the framework of the project the following work will be done: application of semiconductor photocathodes in sources of polarized electrons attached to an electron accelerator; measurement of spinpolarization spectra, of yield spectra, and of life time of photocathodes developed in the project; research on fundamental physics of photoelectron emission from solids; development of new schemes for the production of highly polarized electrons; growth of strained layer III-V-photocathodes and III-V-superlattice structures by MOCVD-techniques; growth of GaAsP-cathodes with optimum of spinpolarization of emitted electrons tuned to powerful laser radiation; theoretical calculations of semiconductor heterostructures suited to spinpolarized photoelectron emission; growth of semiconductor heterostructures applied in spinpolarized photoelectron emission by using liquid phase epitaxy; research on spinpolarized photoemission from III-V-semiconductor compounds; and study of time evolution of the photoemission process.

Invito a presentare proposte

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Meccanismo di finanziamento

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Coordinatore

JOHANNES GUTENBERG UNIVERSITÄT MAINZ
Contributo UE
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Indirizzo
Staudinger Weg 7
55099 Mainz
Germania

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Partecipanti (6)