Pyroelectric and photoelectric responses of capacitors based on thin PZT films

The influence of 0.63-μm laser radiation and an external electric field on the photo-and pyroelectric response of thin ferroelectric Pb(Zr_0.54Ti_0.46)O₃ (PZT) films is studied at various temperatures. The films are grown by RF magnetron sputtering of a PZT ceramic target on platinum-coated substrates. It is found that the photosensitivity of PZT films increases after switching of the applied static electric field, as well as after an increase in temperature.     

Interaction of iron atoms with the Si(100)-2 × 1 surface

Interaction of iron atoms with the Si(100)-2 × 1 surface at room temperature is studied by core-level photoelectron spectroscopy using synchrotron radiation for Fe coverages ranging from a fraction of a monolayer to six monolayers. It is shown that the Fe/Si(100)-2 × 1 interface is chemically active: the Fe-Si solid solution forms early in deposition of iron on silicon. When the Fe coverage reaches four to five monolayers, the state of the system is changed and Fe₃Si silicide arises.     

Hopping conductivity of carbynes modified under high pressures and temperatures: Galvanomagnetic and thermoelectric properties

The conductivity, thermopower, and magnetoresistance of carbynes structurally modified by heating under a high pressure are investigated in the temperature range 1.8–300 K in a magnetic field up to 70 kOe. It is shown that an increase in the synthesis temperature under pressure leads to a transition from 1D hopping conductivity to 2D and then to 3D hopping conductivity. An analysis of transport data at T ≤ 40 K makes it possible to determine the localization radius a ～ (56?140) Å of the wave function and to estimate the density of localized states _g(E _F) for various dimensions d of space: _g(E _F) ≈ 5.8 × 10⁷ eV^?1 cm^?1 (d=1), _g(E _F) ≈5×10¹⁴ eV^?1 cm ^?2 (d=2), and _g(E _F)≈1.1×10²¹ eV^?1 cm_?3 (d=3). A model for hopping conductivity and structure of carbynes is proposed on the basis of clusterization of sp ² bonds in the carbyne matrix on the nanometer scale.     

Synthesis and thermal conversions of unsaturated nickel(II) dicarboxylates as precursors of metallopolymer nanocomposites

Nickel(II) dicarboxylates of unsaturated carboxylic acids (maleic (MalA), itaconic (ItA), acetylenedicarboxylic (ADCA), allylmalonic (AlMalA), glutaconic (GlutA), cis,cis-muconic (MucA) acids) were synthesized and characterized by thermal analysis and IR spectroscopy. The synthesized dicarboxylates were subjected to thermolysis, and the obtained nanocomposites were studied by transmission and scanning electron microscopy and X-ray diffraction. The synthesized metallopolymer nanocomposites were NiO and metallic Ni nanoparticles distributed over a stabilizing matrix. The formation enthalpy of dicarboxylates (ΔН_r^°) was calculated by the PM3 semi-empirical quantum-chemical method. The nanoparticle size was determined, and a relationship between the average nanoparticle diameter (d_avg) and ΔН_r^° was established. The microstructure and magnetic characteristics of the obtained nanocomposites, namely, the maximum and residual magnetization and the coercive force, were studied.     

Formation of interfacial iron silicides on the oxidized silicon surface during solid-phase epitaxy

The early stages of iron silicide formation in the Fe/SiO _x /Si(100) ternary system during solid-phase epitaxy are studied by high-resolution (～100 meV) photoelectron spectroscopy using synchrotron radiation. The spectra of core and valence electrons taken after a number of isochronous heat treatments of the samples at 750°C are analyzed. It is found that the solid-phase reaction between Fe and Si atoms proceeds in the vicinity of the SiO _x /Si interface, which metal atoms reach when deposited on the sample surface at room temperature. Iron silicide starts forming at 60°C. Solid-phase synthesis is shown to proceed in two stages: the formation of the metastable FeSi interfacial phase with a CsCl-like structure and the formation of the stable β-FeSi₂ phase. During annealing, structural modification of the silicon oxide occurs, which shows up in the growth of the Si⁺⁴ peaks and attenuation of the Si⁺² peaks.     

Formation of the Co/Si(110) interface: Phase composition and magnetic properties

The formation of the Co/Si(110)16 × 2 interface and its magnetic properties are studied by high-energy-resolution photoelectron spectroscopy using synchrotron radiation and magnetic linear dichroism in the photoemission of core electrons. It is shown that a cobalt coating less than 7 Å thick deposited on the silicon surface at room temperature results in the formation of an ultrathin (1.7 Å) interfacial cobalt silicide layer and a layer of silicon-cobalt solid solution. The ferromagnetic ordering of the interface is observed at an evaporation dose corresponding to 6–7 Å in which case a cobalt metal film begins to grow on the solid solution layer. During 300°C-annealing of the sample covered by a nanometer-thick cobalt layer, the metal film gradually disappears and four silicide phases arise: metastable ferromagnetic silicide Co₃Si and three stable nonmagnetic silicides (Co₂Si, CoSi, and CoSi₂).     

Normal and anomalous conductivity hystereses in the channel of a transparent ferroelectric transistor

Structures of the transparent ferroelectric field-effect transistor PZT/SnO₂/Al₂O₃ with “normal” and “anomalous” conductivity hystereses of the channel are prepared and investigated. The “normal” modulation loop for these structures is obtained for the first time. Antimony-doped SnO₂/Al₂O₃ epitaxial films evaporated by a YAG laser from a metal target are used as a channel of the field-effect transistor. Ferroelectric PZT films are deposited using magnetron sputtering. The distribution of deep levels at the PZT/SnO₂ interface is measured by the modified relaxation current method. It is established that the ratio between the polarization charge and the trap charge at the PZT/SnO₂ interface critically affects the direction of the conductivity hysteresis of the channel.