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The relaxation dynamics of charge carriers in an epitaxial La[sub 0.7]Ca[sub 0.3]MnO[sub 3] film was studied by the light reflection method with a femtosecond time resolution in a wide temperature range. The relaxation of time-resolved photoinduced reflections was shown to be two-component in the whole temperature range including the paramagnetic dielectric–ferromagnetic metal transition at T ≈ 150–160 K. The fast relaxation component had a maximum lifetime (τ ∼ 500 ps) in the transition region, and its contribution to relaxation increased as temperature decreased. The lifetime of the slow component was minimum (τ ∼ 15 fs) in the transition region. In addition, fast oscillations assigned to coherent phonons appeared in photoinduced responses at T < 200 K. The dephasing time of these oscillations increased as temperature decreased, whereas their frequency changed insignificantly. © 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Polarized micro-Raman measurements were performed to study the phonon modes of Fe, Sb, Al, Ga, and Li doped ZnO thin films, grown by pulsed-laser deposition on c-plane sapphire substrates. Additional modes at about 277, 511, 583, and 644 cm[sup -1], recently assigned to N incorporation [A. Kaschner et al., Appl. Phys. Lett. 80, 1909 (2002)], were observed for Fe, Sb, and Al doped films, intentionally grown without N. The mode at 277 cm[sup -1] occurs also for Ga doped films. These modes thus cannot be related directly to N incorporation. Instead, we suggest host lattice defects as their origin. Further additional modes at 531, 631, and 720 cm[sup -1] seem specific for the Sb, Ga, and Fe dopants, respectively. Li doped ZnO did not reveal additional modes. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]