Cis-polyacetylene films have been synthetized and doped with iodine and antimony penta fluoride, using usual chemical techniques. Doping, leads, after saturation, to conductivity values of about 120 and 25 (Ω cm) -1 at room temperature, respectively for I2 and SbF 5 dopants. The E.S.R. of cis- and trans-, non-doped and doped (CH)x films has been studied. A qualitative analysis of the results allows a better understanding of the electronic properties of these extremely non homogeneous and highly conductive doped polymeric materials

Optoelectrical properties of junctions electrochemically formed on the surface of n‐type CdTe single crystals are reported. The carrier transport process across the junction is controlled by tunnelling through the barrier from one side and by thermal emission followed by recombination at interface states from the opposite side of the junction. The CU characteristics have the shape typical for abrupt junctions and the built‐in potential UD = 1.1 V confirms the formation of an np homojunction covered by a thin Te film. The photovoltaic parameters of these cells are: open‐circuit voltage 0.42 V short‐circuit current density 0.5 to 0.8 mA/cm2, and fill factor 0.54. The spectral response indicate that the thin layer of Te acts only as an optical filter.

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2014 Le dichroisme linéaire de la bande d'absorption à 3950-4000 Å dans BaMnF4 a été étudié dans un domaine de température voisin de la transition de phase structurale. Au premier ordre, le dichroisme linéaire, comme la biréfringence, est proportionnel au carré du paramètre d'ordre. La valeur ainsi obtenue pour 03B2, l'exposant critique du paramètre d'ordre est en accord avec les résultats récents de diffusion de neutrons et en désaccord avec les prédictions de la théorie de Landau. Abstract. 2014 We present here a study of the linear dichroism of the optical absorption band at 3950-4000 Å in BaMnF4 in a temperature range neighbouring the structural phase transition. In first approximation, the linear dichroism, as the linear birefringence is proportional to the square of the order parameter. So we obtain a determination of 03B2, the critical exponent of the order parameter, in good agreement with the last value obtained from neutrons scattering and in disagreement with prediction of Landau theory.