DOI: 10.1051/jp3:1996208
J. Phys. III France 6 (1996) 1697-1704

Improvement of the Electrical Properties of Layered Semiconductor Thin Films by Iodine Treatment

J.C. Bernede¹, H. Hadouda¹, S.J. Li¹, H. Essaidi¹, J. Pouzet¹ and A. Khelil<sup>2

1</sup>  Laboratoire de Physique des Matériaux pour l'Électronique, Équipe Couches Minces et Matériaux Nouveaux, Faculté des Sciences et des Techniques, Université de Nantes, 2 rue de la Houssinière, 44072 Nantes Cedex 03, France
²  Laboratoire de Physique des Matériaux et Composants de l'Électronique, Université d'Oran ès Sénia, BP 1642, Oran, Algeria

(Received 18 March 1996, revised 4 June 1996, accepted 13 September 1996)

Abstract
The conductivity of WSe ₂, MoS ₂, WS ₂ thin films, obtained by solid state reaction between the metal and the chalcogen sequentially deposited, is controlled by grain boundary scattering mechanisms. A mild annealing treatment at 373 K for 1/2 h to 6 h under iodine atmosphere improves the conductivity of the films. In the case of WSe ₂, which gives the better results, the room temperature conductivity can be multiplied by 25. if the conductivity is improved, its dependence with the temperature demonstrates that the conductivity process is still controlled by grain boundary model. Barrier height fluctuations at the grain boundary are introduced to have experimental and theoretical data fit together. After iodine treatment the mean barrier height has decreased and the homogeneity of the films is improved. These improvements are very promising for photovoltaic since it appears that iodine passivates defects at the grain boundaries.

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