scholarly journals Homogeneous versus Inhomogeneous Polarization Switching in PZT Thin Films: Impact of the Structural Quality and Correlation to the Negative Capacitance Effect

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 2124
Author(s):  
Lucian Pintilie ◽  
Georgia Andra Boni ◽  
Cristina Florentina Chirila ◽  
Viorica Stancu ◽  
Lucian Trupina ◽  
...  
Keyword(s):  
Sol Gel ◽  
Polarization Switching ◽  
Switching Process ◽  
Structural Quality ◽  
Negative Capacitance ◽  
Si Substrates ◽  
Structure Changes ◽  
Capacitance Effect ◽  
Transmission Electron ◽  
Electric Force Microscopy

Polarization switching in ferroelectric films is exploited in many applications, such as non-volatile memories and negative capacitance field affect transistors. This can be inhomogeneous or homogeneous, depending on if ferroelectric domains are forming or not during the switching process. The relation between the polarization switching, the structural quality of the films and the negative capacitance was not studied in depth. Here, Pb(Zr0.2Ti0.8)O3 (PZT) layers were deposited by pulse laser deposition (PLD) and sol-gel (SG) on single crystal SrTiO3 (STO) and Si substrates, respectively. The structural quality was analyzed by X-ray diffraction and transmission electron microscopy, while the electric properties were investigated by performing hysteresis, dynamic dielectric measurements, and piezo-electric force microscopy analysis. It was found that the PZT layers grown by PLD on SRO/STO substrates are epitaxial while the layers deposited by SG on Pt/Si are polycrystalline. The polarization value decreases as the structure changes from epitaxial to polycrystalline, as well as the magnitude of the leakage current and of the differential negative capacitance, while the switching changes from homogeneous to inhomogeneous. The results are explained by the compensation rate of the depolarization field during the switching process, which is much faster in epitaxial films than in polycrystalline ones.

Structural Stability of Iron Oxide Nanotubes and an Enhancement of Photo Induced Current Detected in the Complex with Fullerenols

2014 ◽  
Vol 1659 ◽  
pp. 169-174 ◽  
Author(s):  
Shunji Bandow ◽  
Yuki Shiraki
Keyword(s):  
Iron Oxide ◽  
Sol Gel ◽  
Crystallographic Structure ◽  
X Ray Diffraction ◽  
Morphological Transformation ◽  
Diffraction Profile ◽  
Structure Changes ◽  
Transmission Electron ◽  
Inner Diameter ◽  
Gel Technique

ABSTRACTIron oxide nanotubes (Fe-ox-NTs) were prepared by a sol-gel technique using a mixture of an Fe(NO3)3·9H2O and a Pluronic F-127 nonionic surfactant in 1-propanol, gelatinizing at 35 °C for 5 days. Crude nanotubes thus obtained were well rinsed by deionized water in order to remove the surfactant. Transmission electron microscopy showed that the products have tubule structure with the outer (inner) diameter ∼10-15 (∼5-10) nm and the length ∼100 nm. X-ray diffraction profile of the crude nanotubes indicated a broadened feature characteristic for a defective or amorphous-like material, and whose profile may associate with the structure of ɣ-Fe2O3 (maghemite). By heating the crude nanotubes in open air, a phase transition occurs in a defective ɣ-Fe2O3 and its structure changes to a relaxed α-Fe2O3 (hematite) without morphological transformation. A further increase of the temperature results a destruction of the tube structure to the spherical nanoparticles without changing the crystallographic structure. A structurally relaxed Fe-ox-NT complex with fullerenols (C60(OH)n, n∼20) has larger photosensitive response under visible light irradiation, but the crude and defective Fe-ox-NTs and their complexes with fullerenols do not indicate noticeable response.

scholarly journals Structural, Magnetic Properties and Hyperthermia Efficiency of MF/CuAl2O4 Multiferroic Nanocomposite

2021 ◽  
Author(s):  
Roumaih Roumaih ◽  
Ismail Abd-elrahem ◽  
Shaban I. Hussein
Keyword(s):  
Magnetic Properties ◽  
Fourier Transforms ◽  
Sol Gel ◽  
Hysteresis Loops ◽  
Heating Efficiency ◽  
Structure Changes ◽  
Transmission Electron ◽  
Standard Value ◽  
Xrd Patterns ◽  
Two Stages

Abstract The multiferroic MF/CuAl2O4 (MF= CoFe2O4, NiFe2O4, MgFe2O4, and ZnFe2O4) was prepared using two stages of the sol-gel method. X-ray Diffraction (XRD), the Fourier transforms infrared absorption (FT-IR) and High-resolution Transmission Electron Microscope (HR-TEM) were used to examine the structure of all samples. From the XRD patterns, two standards of cubic spinels structure (CuAl2O4 + MF) were observed. The analysis of FTIR spectra confirmed the formation of the chemical and molecular structure changes in the MF/CuAl2O4. HR-TEM images showed a uniform particle distribution with a nanoscale of all samples. The magnetic properties were studied from the hysteresis loops using a vibrating sample magnetometer (VSM) and the magnetization M (T) by the Faraday balance method. All samples exhibited typical ferrimagnetic behavior, except for ZnF/CuAl recorded superparamagnetic. Curie temperature (TC) for all nanocomposites obtained from M(T) protocols, which is lower than the standard value of MF nanoferrites. The heating efficiency of all samples was investigated by measuring the Specific Absorption Rate (SAR) parameter. The SAR of NiF/CuAl showed a maximum value as well as saturation magnetization (Ms) and lowest coercivity (Hc) value.

InAsSb Photodiodes Grown on InAs, GaAs and Si Substrates by Molecular Beam Epitaxy

1990 ◽  
Vol 216 ◽  
Author(s):  
W. Dobbelaere ◽  
J. De Boeck ◽  
W. De Raedt ◽  
J. Vanhellemont ◽  
G. Zou ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Spectral Response ◽  
Structural Quality ◽  
Rutherford Back Scattering ◽  
Si Substrates ◽  
Transmission Electron ◽  
Current Voltage ◽  
K Current

ABSTRACTInAs and InAs0.85Sb0.15p-“i”-n structures were grown on InAs, GaAs and Si substrates by Molecular Beam Epitaxy. The structural quality of the layers is discussed using Transmission Electron Microscopy and Rutherford Back Scattering. The influence of the material quality on the 77 K current-voltage measurements is explained. The spectral response of the devices was measured demonstrating peak responsivities of 2.1 A/W at 3.5μm wavelength for InAs0.85Sb0.15 detectors with a 4.3 μm cut-off wavelength.

Electron Energy Analysis of Germanium and Silica Layers on Silicon Substrates

1975 ◽  
Vol 33 ◽  
pp. 96-97
Author(s):  
R. W. Ditchfield ◽  
A. G. Cullis
Keyword(s):  
Epitaxial Growth ◽  
Electron Energy ◽  
Silicon Substrates ◽  
Secondary Phases ◽  
Si Substrates ◽  
Transmission Electron ◽  
Layer Structures ◽  
Si Films ◽  
Electron Energy Loss ◽  
Growth Centres

An energy analyzing transmission electron microscope of the Möllenstedt type was used to measure the electron energy loss spectra given by various layer structures to a spatial resolution of 100Å. The technique is an important, method of microanalysis and has been used to identify secondary phases in alloys and impurity particles incorporated into epitaxial Si films.Layers Formed by the Epitaxial Growth of Ge on Si Substrates Following studies of the epitaxial growth of Ge on (111) Si substrates by vacuum evaporation, it was important to investigate the possible mixing of these two elements in the grown layers. These layers consisted of separate growth centres which were often triangular and oriented in the same sense, as shown in Fig. 1.

TEM evaluation of graded SixGe1-x heterolayers

1991 ◽  
Vol 49 ◽  
pp. 894-895
Author(s):  
N. David Theodore ◽  
Mamoru Tomozane ◽  
Ming Liaw
Keyword(s):  
Heterojunction Bipolar Transistors ◽  
Gas Flow ◽  
Field Effect Transistors ◽  
Chemical Vapor ◽  
Dark Field ◽  
Bipolar Transistors ◽  
Structural Quality ◽  
Weak Beam ◽  
Transmission Electron ◽  
And Behavior

There is extensive interest in SiGe for use in heterojunction bipolar transistors. SiGe/Si superlattices are also of interest because of their potential for use in infrared detectors and field-effect transistors. The processing required for these materials is quite compatible with existing silicon technology. However, before SiGe can be used extensively for devices, there is a need to understand and then control the origin and behavior of defects in the materials. The present study was aimed at investigating the structural quality of, and the behavior of defects in, graded SiGe layers grown by chemical vapor deposition (CVD).The structures investigated in this study consisted of Si1-xGex[x=0.16]/Si1-xGex[x= 0.14, 0.13, 0.12, 0.10, 0.09, 0.07, 0.05, 0.04, 0.005, 0]/epi-Si/substrate heterolayers grown by CVD. The Si1-xGex layers were isochronally grown [t = 0.4 minutes per layer], with gas-flow rates being adjusted to control composition. Cross-section TEM specimens were prepared in the 110 geometry. These were then analyzed using two-beam bright-field, dark-field and weak-beam images. A JEOL JEM 200CX transmission electron microscope was used, operating at 200 kV.

Influence of MBE Growth Conditions on Dislocation Densities of GaAs/Ge Epilayers Grown on Silicon Substrates

1985 ◽  
Vol 43 ◽  
pp. 364-365
Author(s):  
K.M. Hones ◽  
P. Sheldon ◽  
B.G. Yacobi ◽  
A. Mason
Keyword(s):  
High Efficiency ◽  
Lattice Mismatch ◽  
Low Cost ◽  
Growth Conditions ◽  
Nonradiative Recombination ◽  
Device Structure ◽  
Si Substrates ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Dislocation Type

There is increasing interest in growing epitaxial GaAs on Si substrates. Such a device structure would allow low-cost substrates to be used for high-efficiency cascade- junction solar cells. However, high-defect densities may result from the large lattice mismatch (∼4%) between the GaAs epilayer and the silicon substrate. These defects can act as nonradiative recombination centers that can degrade the optical and electrical properties of the epitaxially grown GaAs. For this reason, it is important to optimize epilayer growth conditions in order to minimize resulting dislocation densities. The purpose of this paper is to provide an indication of the quality of the epitaxially grown GaAs layers by using transmission electron microscopy (TEM) to examine dislocation type and density as a function of various growth conditions. In this study an intermediate Ge layer was used to avoid nucleation difficulties observed for GaAs growth directly on Si substrates. GaAs/Ge epilayers were grown by molecular beam epitaxy (MBE) on Si substrates in a manner similar to that described previously.

Transmission Electron Microscopy characterization of epitaxial III-V semiconductor thin films grown on Si(100) by ion-assisted deposition

1990 ◽  
Vol 48 (4) ◽  
pp. 686-687
Author(s):  
L. Hultman ◽  
C.-H. Choi ◽  
R. Kaspi ◽  
R. Ai ◽  
S.A. Barnett
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ion Irradiation ◽  
High Energy ◽  
Nucleation Mechanism ◽  
Layer By Layer ◽  
Extended Defect ◽  
Island Formation ◽  
Si Substrates ◽  
Transmission Electron

III-V semiconductor films nucleate by the Stranski-Krastanov (SK) mechanism on Si substrates. Many of the extended defects present in the films are believed to result from the island formation and coalescence stage of SK growth. We have recently shown that low (-30 eV) energy, high flux (4 ions per deposited atom), Ar ion irradiation during nucleation of III-V semiconductors on Si substrates prolongs the 1ayer-by-layer stage of SK nucleation, leading to a decrease in extended defect densities. Furthermore, the epitaxial temperature was reduced by >100°C due to ion irradiation. The effect of ion bombardment on the nucleation mechanism was explained as being due to ion-induced dissociation of three-dimensional islands and ion-enhanced surface diffusion.For the case of InAs grown at 380°C on Si(100) (11% lattice mismatch), where island formation is expected after ≤ 1 monolayer (ML) during molecular beam epitaxy (MBE), in-situ reflection high-energy electron diffraction (RHEED) showed that 28 eV Ar ion irradiation prolonged the layer-by-layer stage of SK nucleation up to 10 ML. Otherion energies maintained layer-by-layer growth to lesser thicknesses. The ion-induced change in nucleation mechanism resulted in smoother surfaces and improved the crystalline perfection of thicker films as shown by transmission electron microscopy and X-ray rocking curve studies.

Blue Emitting BaAl2O4:Ce3+ Nanophosphors with High Color Purity and Brightness for White LEDs

2019 ◽  
Vol 25 (6) ◽  
pp. 1466-1470 ◽  
Author(s):  
Rituparna Chatterjee ◽  
Subhajit Saha ◽  
Karamjyoti Panigrahi ◽  
Uttam Kumar Ghorai ◽  
Gopes Chandra Das ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Field Emission ◽  
Sol Gel ◽  
Blue Emission ◽  
Diffraction Field ◽  
White Leds ◽  
Display Devices ◽  
Transmission Electron ◽  
Structure Morphology ◽  
The Impact

AbstractIn this work, strongly blue emitting Ce3+-activated BaAl2O4 nanophosphors were successfully synthesized by a sol–gel technique. The crystal structure, morphology, and microstructure of the nanophosphors have been studied by X-ray powder diffraction, field emission scanning electron microscopy, and high-resolution transmission electron microscopy. The photoluminescence spectra show the impact of concentration variation of Ce3+ on the photoluminescence emission of the phosphor. These nanophosphors display intense blue emission peaking at 422 nm generated by the Ce3+ 5d → 4f transition under 350 nm excitation. Our results reveal that this nanophosphor has the capability to take part in the emergent domain of solid-state lighting and field-emission display devices.

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