Crystallization and related magnetotransport properties of amorphous manganite films grown by metalorganic chemical vapor deposition

摘要

La_(1-x)Sr_(x)MnO_(3) films were grown at 450℃ by pulsed liquid-injection metalorganic chemical vapor deposition on silicon substrates. The films were amorphous and exhibited a high resistivity (>10 kΩ cm). Different kinds of annealing (650℃ for 1, 3, 6, and 10 h, 800℃ for 15 mn, 900℃ for 5 mn, and rapid thermal annealings) were performed in order to achieve crystallization through both variations of nucleation and growth rates. X-ray diffraction and transmission electron microscopy were used to characterize the different microstructures obtained. After annealing, the perovskite La_(1-x)Sr_(x)MnO_(3) (x～0.3) phase was obtained. The resistivity of the films ranged within two orders of magnitude depending on the annealing temperature and time. The magnetoresistive properties were also recovered and similar to those obtained on as-grown polycrystalline films. The rapid thermal annealing process proved to be efficient: the amorphous films exhibited, after a 90 s flash-annealing, an ordering temperature of 340 K, a resistivity of the order of 1 Ω cm, and a low-field magnetoresistance of 20 at 22 K and 0.2 T.