We report preparation and properties of hybrid bilayer structures composed of the organic semiconductor, 8-hydroxyquinoline
aluminum (Alq3), p-type Si and two ferromagnetic oxides, namely, colossal magnetoresistance manganite,
La2/3Sr1/3MnO3 (LSMO), and magnetite (Fe3O4). Thin Alq3 films were thermally evaporated in vacuum. The bottom
LSMO films were grown in-situ at 750°C by dc magnetron sputtering on crystalline SrTiO3 while Fe3O4 films were magnetron sputtered at 400°C on glass. Current versus voltage in a case of vertical current flow has been investigated
for the heterojunctions. The investigations revealed dominating role of thermoionic emission in a barrier of Schottky
type for the Alq3/p-Si heterojunction while a mechanism based on carrier tunnelling through an interface and space
charge limited current processes were considered to explain nonlinear electrical transport in the Alq3/LSMO, Alq3/
Fe3O4 heterojunctions. The Alq3/LSMO demonstrated magnetoresistance values up to 11 % (at T=240 K and B=1 T).
Millimeter wave bridge technique for non-destructive material homogeneity characterization is described. The idea of
this technique is the local excitation of the millimeter waves in the testing material and the measurement of the
transmitted (reflected) wave amplitude and phase in different places of it, i.e. the material plate is scanned by the beam
of the millimeter waves. Same results of the homogeneity measurements for dielectric wafers according to dielectric
constant anisotropy are presented. The measurement technique sensitivity is discussed.
Reversible resistance change of thin La0.67Ca0.33MnO3 films, grown on cleaved MgO substrates, have been investigated
using both dc current and nanosecond electrical pulses of 10 ns and 100 ns in duration. It was found that at T=80 K the
series of 10 ns pulses with electric field strength above 20 kV/cm induced a reversible change of the film from low to
high resistive state. At the same time, the series of 100 ns pulses transmitted through the sample with increased
resistance induced an inverse effect - i.e. transformation of the film to the initial state. It was also obtained that at 130 K
(just below Curie temperature Tc) the series of 100 ns electrical pulses induced the resistive transition at lower electric
field value (13.7 kV/cm). The obtained results were explained in terms of local film heating and strong electric field
effect on narrow conductive constructions during current flow through channels in electrically inhomogeneous media in
the vicinity of Tc.
Thin films of tin-doped indium oxide, In2O3:Sn (ITO), with 9 mol% Sn were grown heteroepitaxially at 600 degree(s)C by dc magnetron sputtering on (100)-faces of lattice-matched yttrium stabilized zirconia, ZrO2:Y (YSZ). Carrier density ranging from about 1026cm-3 to 1027m-3 has been measured after film annealing at 200divided by750 degree(s)C in oxygen or vacuum. The lowest resistivity valued down to about 4.0(DOT)10-6 (Omega) m (at 300 K) have been indicated for the vacuum-annealed films. Optical transmittance and reflectance spectra of the films were investigated at T = 85divided by300 K in the UV, visible and near IR spectra regions ((lambda) = 0.2divided by6.0 micrometers ). The transmittance spectra in the vicinity of the band-gap were modeled in terms of direct allowed transitions taking in to account both the gap widening (the Burstein-Moss effect) and narrowing due to electron-electron and electron-ion interaction. The band- gap Eg0, of 3.47 eV and 3.54 eV has been evaluated for non-doped material at T = 300 K and 85 K, respectively.
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