IVC17 / ICSS13 and ICN+T 2007

La_0.7Ce_0.3MnO₃ thin films surface studied by photoelectron spectroscopy
Mickevicius, Sigitas¹; Bondarenka, Vladimiras¹; Grebinskij, Sergej¹; Senulis, Mindaugas¹; Tvardauskas, Henrikas¹; Vengalis, Bonifacijus¹; Oginskis, Antanas¹; Orlowski, Bronislaw²; Osinniy, Wiktor²; Pietrzyk, Mieczyslaw²; Drube, Wolfgang³ ¹Lithuania; ²Poland; ³Germany

In the last decade the hole-doped manganites in the form of La_1-xA_xMnO₃ (A-divalent cation) have been intensive studied for the practical application potential. On the other hand, the electron-doped manganites with doping a tetravalent cation as Ce or others, in which the valence state of manganese should be divalent and trivalent state, have not been so well investigated. In this paper La_0.7Ce_0.3MnO₃ (LCeMO) thin films were prepared on lattice matched single-crystal NdGaO₃ (100) by a reactive dc magnetron sputtering. During film growth, temperature of the substrate was held fixed (T = 650 / 750°C), and Ar-O₂ gas mixture pressure was kept at about 15 Pa and in order to find the optimum gas mixture, several Ar:O₂ ratios (0.25:0.75, 0.5:0.5 and 0.75:0.25) were used for deposition. After film deposition, the growth chamber was vented with pure oxygen (1 atm.) and the films were cooled down slowly to a room temperature. Thickness of the films was about 100 nm.
The high-resolution XRD spectra measurements demonstrating high crystalline quality of La_0.7Ce_0.3MnO₃thin films and a negligible amount of CeO2 phase. The XPS data were obtained with the tunable high-energy X-ray photoelectron spectrometer at the beam line BW2 of HASYLAB (Hamburg) and laboratory X-ray source XSAM 800 (KRATOS Analytical, UK).
The analyis of obtained date indicate that Ce ions are in tetravalent and trivalent chemical states in LCeMO films. The Mn 2p spectra analysis shown that the manganese present in divalent, trivalent and tetravalent chemical states in the as-prepared films. The reduction of LCeMO films increase trivalent cerium and divalent manganese ions concentration. The lanthanum ions are trivalent and subsist in oxide and hydroxide chemical states in LCeMO thin films.

back