Optical and electrical properties of amorphous and nanocrystalline (La0.8Sr0.2)0.9MnO3 thin films prepared from low-temperature processing technique

The results of a study on the optical and electrical properties of (La0.8Sr0.2)(0.9)MnO3 (LSM) thin films obtained by a polymeric precursor spin coating technique were presented. This method allowed preparation of optical quality thin films at annealing temperatures around 800 degrees C. Amorphous and crystalline LSM thin films were studied by optical and electrical conductivity measurements. The energy-dependent absorption coefficients for the crystalline specimen were calculated from optical spectra and extra absorption was observed in the range of 1.8-2.5 eV with the exchange-gap excitation behavior in the 3-5 eV range. In comparison to the amorphous specimens, the electrical conductivity of the nanocrystalline specimen increased two to three orders of magnitude with decreasing activation energy. The charge carrier absorption model suggested an increase of the carrier concentration in the nanocrystalline specimen which may be a reason for the change in the electrical conductivity.