Impedance studies on high energy Li3+ irradiated PZT thin films

The ferroelectric Pb(Zr0.48Ti0.52)O3 (PZT) thin films prepared by the pulsed laser deposition technique were studied for their response to high energy lithium ion irradiation through impedance spectroscopy. The Debye peaks, observed in the impedance and modulus plots of irradiated films, shifts towards higher frequencies compared to those of unirradiated films. This is equivalent to the trend observed with increase in temperature in the unirradiated films due to the dielectric relaxation. The irradiated films showed a decrease in the grain resistance compared to the unirradiated films. The activation energy of dielectric relaxation increases from 1.25 eV of unirradiated film to 1.62 eV of irradiated film. The observed modifications in the irradiated film were ascribed to the modifications in the grain structure due to the high value of electronic energy loss. © 2009 Elsevier B.V. All rights reserved

Current transport behaviour of Au/n-GaAs Schottky diodes grown on Ge substrate with different epitaxial layer thickness over a wide temperature range

The work presents temperature dependent forward and reverse current-voltage (I-V) analyses of n-GaAs/Au Schottky Diodes grown on n+ Ge substrate with different epitaxial layer thicknesses. While some of the Schottky diodes follow TED mechanism, others exceed significantly from this theory due to existence of patches of reduced barrier height embedded in the Schottky interface. The zero bias barrier heights (φbo) increase (0.649 to 0.809 eV) while the ideality factors (η) decrease (1.514 to 1.052) with increase in epitaxial layer thickness (1-4 μm), thus, indicating similar behaviour to that observed for the I-V characteristics of the undertaken Schottky diodes with decreasing temperature. It all indicated the existence of barrier inhomogenities over the M-S interface. The breakdown behaviour analysis of these diodes showed some interesting results; the breakdown voltage (VBR) decreases with temperature and shows ‘Defect Assisted Tunneling’ phenomenon through surface or defect states in the 1 μm thick epitaxial layer Schottky diode while VBR increases with temperature in 3 μm and 4 μm thick epitaxial layer Schottky diodes which demonstrate ‘Avalanche Multiplication’ mechanism responsible for junction breakdown. The reverse breakdown voltage is also seen to increase (2.7-5.9 Volts) with the increase in epitaxial layer thickness of the diodes. The undertaken diodes have been observed to follow TFE mechanism at low temperatures (below 200 K) in which the tunneling current component increases with epitaxial layer thickness which has been ascribed as an impact of GaAs/Ge hetero-interface over the Au/n-GaAs Schottky barrier. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2788

Pt/Ti/SiO2/Si substrates

Pt/Ti/SiO2/Si structures have been studied to investigate the structural, chemical, and microstructural changes that occur during annealing. Grain growth of the as-deposited Pt columns was observed after annealing at 650 °C, and extensive changes in the Pt microstructure were apparent following a 750 °C anneal for 20 min. In addition, two types of defects were identified on the surfaces of annealed substrates. Defect formation was retarded when the surface was covered with a ferroelectric film. Concurrent with the annealing-induced Pt microstructure changes, Ti from the adhesion layer between the Pt and the SiO2 migrated into the Pt layer and oxidized. It was shown with spectroscopic ellipsometry and Auger electron spectroscopy that for long annealing times, the titanium oxide layer can reach the Pt surface. Consequently, at the processing temperatures utilized in preparing many ferroelectric thin films, the substrate is not completely inert or immobile. The changes associated with Ti migration could be especially problematic in techniques that require the substrate to be heated prior to film depositio

Magnetocapacitive La0.6Sr0.4MnO3 0.7Pb(Mg0.33Nb0.67)O3 0.3PbTiO3 epitaxial heterostructures

Epitaxial heterostructures of La0.6Sr0.4MnO3 0.7Pb(Mg0.33Nb0.67)O3 0.3PbTiO3 were fabricated on LaNiO3 coated LaAlO3 (100) substrates by pulsed laser ablation. Ferromagnetic and ferroelectric hysteresis established their biferroic nature. Dielectric behviour studied under different magnetic fields over a wide range of frequency and temperatures revealed that the capacitance in these heterostructures varies with the applied magnetic field. Appearance of magnetocapacitance and its dependence on magnetic fields, magnetic layer thickness, temperature and frequency indicated a combined contribution of strain mediated magnetoelectric coupling, magnetoresistance of the magnetic layer and Maxwell Wagner effect on the observed properties

Impedance studies on oxygen ion irradiated PZT thin films

Impedance spectroscopy was used to study the effects of 70 MeV O ion irradn. on ferroelec. Pb(Zr0.48Ti0.52)​O3 (PZT) thin films prepd. by the pulsed laser deposition. The impedance and modulus plots of the unirradiated films reveal that the Debye peaks shift to higher frequencies with the increase in temp. due to the well-​known dielec. relaxation mechanism. After O ion irradn., Debye peaks shift towards lower frequency compared to those of unirradiated films indicating ion beam induced modifications in dielec. relaxation. The grain resistance estd. from the complex impedance plots was obsd. to be increased after irradn. The activation energy of dielec. relaxation increases with irradn. and show fluence dependant increase. The obsd. modifications in the irradiated films were ascribed to the modifications in the grain structure due to the high value of electronic energy loss