Misted Deposition of [3D] Trenches for Drams and Frams III. PZT Thin Films and PZT Nanotubes
Pb(Zr,Ti)O3 (PZT) thin films and nanotube were prepared on SiO2/Si substrates by liquid source misted chemical deposition (LSMCD) using Samco MD-6060 apparatus. We report the deposition and characterization of transparent ferroelectric thin films and nanotubes. PZT thin films deposited at ambient conditions and annealing at 700degC exhibit good ferroelectric properties with remanent polarisation of ca. 15 muC/cm2. The step coverage was 59% on the side wall and 79% on the bottom wall.
Ferroelectric Nanotubes
: We report the independent invention of ferroelectric nanotubes from groups in several countries. Devices have been made with three different materials: lead zirconate-titanate PbZr 1-x Ti x O 3 (PZT); barium titanate BaTiO 3 ; and strontium bismuth tantalate SrBi 2 Ta 2 O 9 (SBT). Several different deposition techniques have been used successfully, including misted CSD (chemical solution deposition) and pore wetting. Ferroelectric hysteresis and high optical nonlinearity have been demonstrated. The structures are analyzed via SEM, TEM, XRD, AFM (piezo-mode), and SHG. Applications to trenching in Si dynamic random access memories, ink-jet printers, and photonic devices are discussed. Ferroelectric filled pores as small as 20 nm in diameter have been studied.
Two-dimensional gravitational anomalies, Schwinger terms and dispersion relations
Abstract We are dealing with two-dimensional gravitational anomalies, specifically with the Einstein anomaly and the Weyl anomaly, and we show that they are fully determined by dispersion relations independent of any renormalization procedure (or ultraviolet regularization). The origin of the anomalies is the existence of a superconvergence sum rule for the imaginary part of the relevant formfactor. In the zero mass limit the imaginary part of the formfactor approaches a δ-function singularity at zero momentum squared, exhibiting in this way the infrared feature of the gravitational anomalies. We find an equivalence between the dispersive approach and the dimensional regularization procedure. The Schwinger terms appearing in the equal time commutators of the energy momentum tensors can be calculated by the same dispersive method. Although all computations are performed in two dimensions the method is expected to work in higher dimensions too.