J. Phys. I France 5 (1995) 699-705
Electrical Properties of a Synthetic Pyrite FeS 2 Non Stoichiometric CrystalM. Morsli1, A. Bonnet1, L. Cattin1, A. Conan1 and S. Fiechter2
1 Laboratoire de Physique des Matériaux pour l'Electronique (E.A. 1153), Faculté des Sciences et des Techniques, 2 rue de la Houssinière, 44072 Nantes Cedex 03, France
2 Hahn Meitner Institut Berlin Gmbh, Postfach 390128, Glienicker Strabe 100, 14109 Berlin, Germany
(Received 20 July 1994, revised 13 December 1994, accepted 2 March 1995)
FeS 2 attracts interest as a novel semiconducting material for photovoltaic energy conversion. Electrical conductivity and thermoelectric power (TEP) S have been measured in a wide temperature range (80 - 500 K) on a FeS single crystal which was prepared by vapour transport with bromine as transport reagent (CVT). The experimental results are analysed with the help of a n-type semiconductor model with a donor level originating from (S-Br) 2- centres. The random potential due to the charged lacunar and impurity sites induces the broadening of the donor level into a narrow band. It is shown that the current carriers which take part in the conduction processes are only electrons in the conduction band where they are scattered by acoustical phonons and neutral impurities and electrons in the bromine narrow band in the form of thermally activated hopping.
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