Far infrared response of α- and αt-(BEDT-TTF)2I3

The temperature dependence of the reflectivity of α- and αt-(BEDT-TTF)2I3 was determined in the 10-700 cm-1 range. Moreover the transmission spectra of α-phase between 10 and 33 cm-1 were studied. Using Kramers-Kronig analysis the IR conductivity and permittivity were calculated. The similarity of α t and β-phases was confirmed. The spectra in the metallic phase are dominated by a broad electronic peak between 200 and 500 cm-1 which can be understood as due to transitions across the small gap whose origin is discussed. In the spectra a rich phonon peak structure is observed, mostly of vibronic origin. It is suggested that non totally symmetric modes of BEDT-TTF molecule can couple with electrons.On a déterminé la dépendance en température de la réflectivité des phases α et αt de (BEDT-TTF)2I3 dans le domaine 10-700 cm-1. En outre, on a étudié les spectres de transmission de la phase α entre 10 et 33 cm-1. La conductivité infrarouge et la permittivité ont été calculées au moyen d'une analyse Kramers-Kronig. Des similarités ont été notées entre les phases αt et β. Des transitions à travers un petit gap (dont l'origine reste à discuter) permettent d'interpréter le pic élargi de la phase métallique situé entre 200 et 500 cm-1. Une structure foisonnante en pics est attribuée à des effets vibroniques. Nous suggérons que des modes impartiellement symétriques de la molécule BEDT-TTF peuvent être couplés aux électrons

PLD prepared bioactive BaTiO₃ films on TiNb implants

Abstract BaTiO₃ (BTO) layers were deposited by pulsed laser deposition (PLD) on TiNb, Pt/TiNb, Si (100), and fused silica substrates using various deposition conditions. Polycrystalline BTO with sizes of crystallites in the range from 90 nm to 160 nm was obtained at elevated substrate temperatures of (600 °C–700 °C). With increasing deposition temperature above 700 °C the formation of unwanted rutile phase prevented the growth of perovskite ferroelectric BTO. Concurrently, with decreasing substrate temperature below 500 °C, amorphous films were formed. Post-deposition annealing of the amorphous deposits allowed obtaining perovskite BTO. Using a very thin Pt interlayer between the BTO films and TiNb substrate enabled high-temperature growth of preferentially oriented BTO. Raman spectroscopy and electrical characterization indicated polar ferroelectric behaviour of the BTO films