Deep level transient spectroscopy studies on BaTiO<SUB>3</SUB> and Ba<SUB>1-x</SUB>Ca<SUB>x</SUB>TiO<SUB>3</SUB> thin films deposited on Si substrates

Laser ablation grown BaTiO3 and Ba1-xCaxTiO3 thin films were studied in the metal-ferroelectric-semiconductor configuration by the deep level transient spectroscopy (DLTS) technique. The capture cross section, bulk and interface traps were determined from the DLTS technique. The distributions of calculated interface states were mapped with the silicon energy band gap for both the thin films. The interface states of the Ba1-xCaxTiO3 thin films were found to be higher than the BaTiO3 thin films. The substitution of Ca2+ into the Ba2+ sites of BaTiO3 results in a decreased lattice constant, thereby leading to shrinkage in the unit cell. This might be one of the reasons for the higher density of interface states present in Ba1-xCaxTiO3, as it leads to a large number of unsaturated bonds at the interface of Si substrate-thin films. The calculated capture cross section of the interface traps in both the BaTiO3 and Ba1-xCaxTiO3 thin films was very low in the range of 10-21 cm2

Fabrication, structural characterization, and formation mechanism of ferroelectric SrBi<SUB>2</SUB>Ta<SUB>2</SUB>O<SUB>9</SUB> nanotubes

A capillary-enforced template-based method has been applied to fabricate strontium bismuth tantalate (SrBi2Ta2O9, SBTO) nanotubes (diameter ~200 nm) by filling SBTO precursor solution into the nanochannels of porous anodic aluminum oxide (AAO) templates. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) equipped with Energy-dispersive X-ray spectroscopy (EDX) have been employed to characterize the morphology, structure, and composition of as-prepared nanotubes. XRD and selected-area electron diffraction (SAED) investigations demonstrated that postannealed (650 &#176; C for 1 h) SBTO nanotubes were polycrystalline with an orthorhombic perovskite crystal structure. The FE-SEM and TEM results showed that uniform length and diameter of SBTO nanotubes were obtained. The thickness of the SBTO nanotube walls was about 30 nm. High resolution TEM (HRTEM) analysis confirmed that the obtained SBTO nanotubes are made of randomly aligned nanoparticles 5-10 nm in size. EDX analysis demonstrated that stoichiometric SrBi2Ta2O9 was formed. The possible formation mechanism of SBTO nanotubes in the AAO template is discussed

Synthesis and structural characterization of the antiferroelectric lead zirconate nanotubes by pulsed laser deposition

For the first time, a pulsed laser ablation deposition (PLD) method has been employed for the synthesis of antiferroelectric lead zirconate, PbZrO3, (PZ) nanotubes within the pores of anodic aluminum oxide (AAO) templates. The structure and morphology of fabricated PZ nanotubes were characterized by number of techniques, including scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM)analysis. After postannealing at 650 &#176;C, the PZ nanotubes exhibited a polycrystalline microstructure, and X-ray diffraction studies revealed that they are of an orthorhombic distorted perovskite crystal structure. TEM analysis confirmed that the obtained PZ nanotubes are composed of nanoparticles in the range of 3-7 nm and the thickness of the wall of the nanotubes is around 10 nm

Synthesis and studies of Pb<SUB>0.76</SUB>Ca<SUB>0.24</SUB>TiO<SUB>3</SUB> nanoparticles derived by sol-gel

Pb0.76Ca0.24TiO3 (PCT24) nanoparticles were synthesized by modified sol-gel method and characterized by a number of experimental techniques such as X-ray diffraction, TGA-DTA, FTIR and transmission electron microscopy equipped with energy-dispersive X-ray spectroscopy (EDX). X-ray diffraction (XRD) and selected-area electron diffraction (SAED) investigations demonstrated that the postannealed (650 &#176; C for 1 h) PCT24 nanoparticles have tetragonal perovskite crystal structure. TEM have been employed to characterize the morphology, structure and composition of the as prepared nanoparticles. Dielectric results indicates the evidence for relaxor type behavior while observed leaky ferroelectric loops may be because of the defects such as grain boundaries and the pores in the sample as the sample was not heated at higher temperature, to retain the nanosize dimension of the particles

Biferroic YCrO3

YCrO3 which has a monoclinic structure, shows weak ferromagnetism below 140 K (TN) and a ferroelectric transition at 473 K accompanied by hysteresis. We have determined the structure and energetics of YCrO3 with ferromagnetic and antiferromagnetic ordering by means of first-principles density functional theory calculations, based on pseudopotentials and a plane wave basis. The non-centrosymmetric monoclinic structure is found to be lower in energy than the orthorhombic structure, supporting the biferroic nature of YCrO3.Comment: 16 pages including figure

Studies on hot-filament chemical vapor deposition grown graphene sheets

Graphene was grown on high purity Cu foils using hot-filament chemical vapor deposition method. The foils were kept directly below the tungsten filament and the whole assembly was kept inside a vacuum chamber. CH4 and H2 were used as precursor gases and were allowed to shower on a hot filament, which was kept at a predetermined temperature. The optimization of the process parameters such as gas flow rates, temperature, durations, etc. was done to grow single layer and multilayer graphene. The graphene was characterized using optical microscopy, field emission scanning electron microscopy and micro-Raman spectroscopy techniques. The graphene layers grown at different methane flow rates are shown in Figure 1. By varying the methane flow rates, graphene domains of different sizes and shapes were achieved and are clearly evident from Figures 1a-c. The curved white lines (Figure 1a) present in the FESEM micrographs correspond to Cu terraces. The graphene grown on Cu foils was successfully transferred to SiO2 substrate and the micrograph of which is shown in Figure 1d. The presence of D, G and G’ bands in the Raman spectrum confirmed the growth of graphene in the Cu foil (Figure 2)

Decision Tree to Guide Chronic Kidney Disease Patients at Incipient Stage

Background: The etiologies of kidney disease are sequential and interlinked. They are known as disease markers. The Decision Tree representing initial symptoms needs to be popularized to seek prophylactic measures and educate the community health workers. Material and Methods: Chronic Kidney Disease dataset containing two classes, namely CKD and not CKD was retrieved from UC Irvine Machine Learning Repository available from https://archive.ics.uci.edu/ml/index.php. This dataset includes 400 instances and 25 attributes related to the CKD. The CKD dataset was saved in ARFF format. J48 algorithm was chosen from the WEKA software tool to develop the Decision Tree. Results: The Decision Tree comprises root nodes, branches, internal nodes, and leaf nodes. The root node began in J48 classifier with ‘sc’ (serum creatinine). This node gave two branches, of which one branch led to the internal node ‘pe’ (pedal edema) (sc1.2) ended with a leaf node showing the condition CKD. The internal node ‘pe’ further yielded two branches, the branch with pedal edema terminated with CKD and the branch with no pedal edema led to the internal node. Internal node with ‘dm’ (diabetes mellitus) showed two more branches namely ‘yes’, which lead to CKD, and branch ‘no’ ‘dm’ led to another internal node namely hemo (haemoglobin). In continuation, the nodes for yet another two disease markers, namely hemoglobin and specific gravity of serum of people prone to kidney diseases, were shown at the terminal end of the Decision Tree. Conclusion: The Decision Tree developed for the CKD dataset by using J48 classifier would guide prospective patients with their clinical data reports

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