Electrical characterization of MOCVD grown epitaxial and polycrystalline PLT thin films

Ferroelectric thin films with high charge storage density, low leakage current density and extremely high dielectric constant hold a very special promise for non-volatile memory applications. In this paper we report on the electrical properties of PLT (lanthanum modified lead titanate) thin films exhibiting varying degrees of epitaxy or texture. The films were deposited on sapphire substrates using the metal organic vapor deposition method (MOCVD). The dielectric properties of these films were measured as a function of frequency, AC voltage and DC bias voltage as well as temperature. Leakage current characteristics and hysteresis behavior are also reported. Epitaxial films are found to have a dielectric constant around 900 and almost no frequency dispersion, while polycrystalline films showed a large frequency dispersion with dielectric constants ranging from 4000 at low frequencies to 1100 at the highest frequencies. Epitaxial films had correspondingly lower dissipation factors and lower leakage currents and much narrower hysteresis loops than the polycrystalline films which make them more suitable for DRAM memories