Interfacial Transition Layer Research Articles

Spectral description of fluctuating electromagnetic fields of solids using a self-consistent approach

Another way to evaluate the spectral-correlation properties of thermal fields of solids is suggested. Such a method takes into account detailed structure of the interface transition layer separating one bulk region from those of the vacuum region. The principal element here is the surface linear response function of an arbitrary inhomogeneous electron subsystem of solids. Along with straightforward using the known response functions, for example in a hydrodynamic approach, the suggested method allows calculating the response functions self-consistently based on the time dependent density functional theory. The self-consistent calculation of the linear response function followed by an application of the fluctuation-dissipation theorem yield in the spectral power densities of the fluctuating charge and current correlation functions. The final step of this sequence of actions aiming in obtaining the spectral-correlation properties of thermal fields of solids at any distances.

Angle-resolved photoelectron spectroscopy study on interfacial transition layer and oxidation-induced residual stress in Si(1 0 0) substrate near the interface

Transition layer formed between SiO2 and Si substrate were clarified by XPS.Compositional transition layer (CTL) consists of the 1st CTL and the 2nd CTL.The β-Si is closely correlated with the oxidation-induced residual stress. The angle-resolved Si 2p photoelectron spectra arising from transition layer formed between bulk SiO2 and bulk Si(100)-substrate were measured with probing depth of nearly 2nm. The influence of oxidation temperature in the range from 900?C to 1050?C, annealing in forming gas at 400?C, and oxidation using oxygen radicals at 400?C on the chemical structures of interfacial transition layer were clarified. It was found for the thermally grown interfacial transition layer that two compositional transition layers (CTLs) are formed on the oxide side of the CTL/Si interface and the oxidation-induced chemical structures are formed on the Si substrate side of the interface. Furthermore, a part of the oxidation-induced chemical structures in the Si substrate near the interface was found to be closely correlated with the oxidation-induced residual stress near the interface.

Chemical Structure of Interfacial Transition Layer Formed on Si(100) and Its Dependence on Oxidation Temperature, Annealing in Forming Gas, and Difference in Oxidizing Species

The angle-resolved Si 2p photoelectron spectra arising from a interfacial transition layer formed on a Si(100) were measured with a probing depth of nearly 2 nm. The novel analytical procedure of these spectra was developed by considering that one SiO2 monolayer, two compositional transition layers (CTLs), and one Si monolayer constituting the Si substrate surface are continuously connected with each other to maintain the areal density of Si atoms. It was found for thermally grown transition layers that two CTLs are formed on the oxide side of the CTL/Si interface and the chemical structures correlated with the residual stress appear on the Si substrate side of the interface. The effects of oxidation temperature in the range from 900 to 1050 °C, annealing in the forming gas, and oxidation using oxygen radicals on the chemical structures of transition layers formed on both sides of the interface were also clarified.

Electron-Trap and Hole-Trap Distributions in Metal/Oxide/Nitride/Oxide/Silicon Structures

Distributions of both electron traps and hole traps in metal/oxide/nitride/oxide/silicon (MONOS) structures were studied. These trap distributions were analyzed by using a combination of an avalanche-injection method and capacitance-voltage measurement. The thicknesses of the nitride layers in the MONOS capacitors were varied. It was found that electron traps are mainly located at both the top and bottom oxide/nitride interfaces, whereas hole traps are located at the interfaces as well as in the nitride bulk. This analysis clarified that electron-trap capability decreases anomalously in the range of nitride thickness of less than 4 nm. Moreover, the effective activation energy of electron emission also decreases at nitride thickness less than around 5 nm. These decreases are considered to be accounted for by detrapping due to the Coulomb repulsion between electrons at both interfaces and electron trapping in the interfacial transition layers.

Investigation of Relationship between Interface State and Random Telegraph Noise Using Metal–Oxide–Semiconductor Field-Effect Transistors Fabricated on Si(100), (110), and (111) Substrates

It is clarified that suboxides and interface traps are closely linked to threshold-voltage variation (ΔVth) due to random telegraph noise (RTN) from an investigation of dependence of ΔVth on silicon-surface orientation: Si(100), (110), and (111). The amount of RTN traps increases with increasing amount of suboxides in the interfacial transition layer. With regard to the total amount of suboxides, the Si(110) surface orientation gives a larger amount than Si(100) and Si(111). Furthermore, we found that Si(110) has the potential to give fast RTNs with a larger ΔVth than Si(111). Accordingly, ΔVth for Si(110) is larger than those of Si(100) and Si(111). Attention should be paid to the possibility of the impact of RTN on Si(110) as the vertical plane of a three-dimensional device.

Interface Oxidative Structural Transitions in Graphene Growth on SiC (0001)

The structural transition from a three-dimensional SiC lattice to a two-dimensional graphene sheet is a crucial element in the growth mechanism of graphene on SiC. An interfacial defective transition layer near the surface of the SiC substrate is believed to be an intermediate structure for graphene layer formation. The transition layer consists of SiOxCy, vacancies, and other defects in the SiC lattice, which result from Si evaporation via thermal degradation of the SiC lattice and oxidation reactions of residual oxygen and other oxygen containing molecules on the SiC surface at high temperatures. This partially oxidized and structurally degraded SiC lattice layer is formed at temperatures lower than the graphene growth temperature but then decomposes with increasing temperature, leading to graphene formation. Then, the growth mechanism for graphene on SiC (0001) in high vacuum consists of multiple steps, including Si removal by thermal decomposition and oxidation, collapsing of the near surface SiC latt...

Effects of heterogeneous interfaces on microstructure and dielectric properties of Ca(Mg1/3Nb2/3)O3/CaTiO3 multilayered thin films

The effects of heterogeneous interfaces on the microstructure, the morphology and the dielectric properties of Ca(Mg1/3Nb2/3)O3/CaTiO3(CMN/CT) multilayered(ML) thin film prepared in the layer-by-layer mode with a certain thickness are investigated. According to the experimental results, an equivalent circuit of CMN/CT ML thin film is simulated, and the theoretical formulae of the dielectric constant and loss of thin film are established. The results indicate that CMN/CT ML thin film, in which CT and CMN phases can exist independently, possesses a pure orthorhombic perovskite structure, dense smooth surfaces and intermediate layers at the heterogeneous interfaces, and that the dielectric constant increases and the dielectric loss decreases with the increase in the number of heterogeneous interfaces, and reducing the thickness of the interfacial transition layer is useful to improve the dielectric properties of CMN/CT multilayered thin film.

Role of interfacial transition layers in VO2/Al2O3 heterostructures

Epitaxial VO2 films grown by pulsed laser deposition (PLD) on c-cut sapphire substrates ((0001) Al2O3) were studied by aberration-corrected scanning transmission electron microscopy (STEM). A number of film/substrate orientation relationships were found and are discussed in the context of the semiconductor-metal transition (SMT) characteristics. A structurally and electronically modified buffer layer was revealed on the interface and was attributed to the interface free-energy minimization process of accommodating the symmetry mismatch between the substrate and the film. This interfacial transition layer is expected to affect the SMT behavior when the interfacial region is a significant fraction of the VO2 film thickness.

Formation of transition layers at metal/perovskite oxide interfaces showing resistive switching behaviors

The authors have investigated the chemical states at the interface of metal/perovskite oxides both with and without bipolar resistive switching (RS) behavior using photoemission spectroscopy and x-ray absorption spectroscopy. Al/Pr0.7Ca0.3MnO3 (PCMO), Al/La0.7Ca0.3MnO3 (LCMO), and Al/La0.33Sr0.67FeO3 interfaces were chosen as typical examples of interfaces for the perovskite-based resistance random access memory (ReRAM), while Pt/PCMO and Ag/LCMO were chosen as references for the metal/perovskite interface without RS behavior. Detailed analyses of spectroscopic data revealed that transition layers were formed at the interfaces showing RS behavior as a result of interfacial redox reactions between the Al electrodes and the transition metal ions in the oxides. On the other hand, for the interfaces that did not exhibit RS behavior, no chemical reaction occurred at the interface. The formation of the interfacial transition layer is naturally explained by considering the redox potential between the electrode materials and transition metal ions. These results suggest that a suitable combination of electrodes and oxides could be designed based on their redox potentials.

Quantitative Discussion on Electron-Hole Universal Tunnel Mass in Ultrathin Dielectric of Oxide and Oxide-Nitride

MOS and MIS capacitor has been extensively studied in past several decades by many authors. It has been expected to reveal how basic physics relate electron device operation. In this structure, several physical phenomena co-work and then exhibit the electrical properties measured in IV- and CV-characteristics. On the other hand, the conventional models were established separately for the inversion layer (positive gate voltage), the depletion region (negative-low gate voltage), and the accumulation region (negative-high gate voltage). In addition, actual MOS/MIS samples have interfacial transition layer where physical properties are gradually changed from Si to oxide or other dielectric, the varying composition ratio of molecules and local traps owing to atomistic dangling bonds through dielectric layer. What will happen if we self-consistently unify all the physical models that are separately developed?

Interface and defect characterization in hot-pressed ZrB 2-SiC ceramics

ZrB 2 is interesting for thermal protection materials because of favorable thermal stability, mechanical properties and oxidation resistance. ZrB 2-20 vol.% SiC composite was prepared by hot-pressing at 2000 °C and 30 MPa. Microstructures and interfacial characterization were investigated by high resolution transmission electron microscopy. SiC polytype was formed as 6H structure in hot-pressed ZrB 2-SiC ceramics. Numerous edge dislocations were found in ZrB 2 grains. There was no interfacial amorphous layer or transition layer at the ZrB 2/6H-SiC interface. Note also that since only one of the constituents (ZrB 2 or SiC) was oriented along a proper zone axis, no evident orientation relationship was observed between SiC or ZrB 2.

Properties of Interface Structure between Ultra-Thin White Topping and Old Concrete Pavement

The research of this paper focused on bond characteristics of overlay-substrate interface in ultra-thin white topping(UTW), aim at ultra-thin concrete overlay on old concrete. Compressive and shear stress have been considered in the structural analysis and experimental research. Bonding behaviors of several surface pretreatments to old concrete have been investigated. A shear-peel test device has been developed to imitate brake-load of wheels at the plate boundary of UTW, and its analytical calculate principle have been discussed to simulate the mechanical theory of the shear peel test. Structural analysis and experimental research results indicate that various flaws are accumulated remarkably in the transition layer at overlay-substrate interface in UTW. Different surface pretreatments of the old concrete will influence on the bonding characteristics of overlay-substrate interface, chiseling treatment for interface has more contribution to working together with the new concrete, but interface adhesive agent enhances the coordination between the interface and the old concrete layer. The treatment combination of chiseling and brushing interface adhesive can effectively improve the strength of the weak interface transition layer. Shear-peel test results indicate that the interlocking influence generated by chiseling treatment is prior to brushing interface adhesive. It is necessary turn to account suitable measure to prevent ultra-thin concrete overlay peeling off from old concrete.

Interfacial chemical states of resistance-switching metal/Pr0.7Ca0.3MnO3 interfaces

The relationship between interfacial chemical states and resistance-switching (RS) behaviors at the metal/Pr0.7Ca0.3MnO3 (PCMO) interfaces has been studied by photoemission spectroscopy and x-ray absorption spectroscopy. For Al/PCMO interfaces that exhibit RS behavior, redox reactions between Al and Mn ions occur at the interface. In sharp contrast, no chemical reactions occur at Pt/PCMO interfaces that do not exhibit RS behavior. These results strongly suggest that the interfacial transition layer due to the redox reactions is responsible for the RS behavior at metal/PCMO interfaces.

Universal Tunnel Mass and Charge Trapping in $[( \hbox{SiO}_{2})_{1-x} (\hbox{Si}_{3}\hbox{N}_{4})_{x}]_{1-y}\hbox{Si}_{y}$ Film

Although the tunnel mass is indispensable to predict the gate leakage current of electron devices, it has been regarded as an adjustable parameter to fit the calculated leakage current with the measured ones. This appears useful because it enables calculation of the tunnel current while ignoring some details in advanced device modeling, even though it has veiled the intuitive nature of the modeling. More concretely, the adjustable tunnel mass pushes us to ignore the related issues that should carefully be considered. In this paper, we extract the tunnel masses for electrons and holes from an individual experiment and find that they are 0.85 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , where <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the rest electron mass, irrespective of the molecular compound ratio between Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> and SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and the film thickness. This suggests a convincing model for charge trapping in [(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> (Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> ] <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-y</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> including interfacial transition layers. It is also found that the leakage mechanism is the direct tunneling enhanced by the trapped positive charge.

The Novel Ionic Transfer Detecting Methodology of Lithium Polymer Battery by Positron Annihilation Studies

A new method for ionic transfer detection is called Doppler Broadening S parameter of Positron Annihilation Spectroscopy (PAS) is used to study polysiloxane electrolytes with ethylene oxide (EO) side chains and carbonate electrolytes. First, the polymer electrolytes are modified to enhance contact with an acrylate, and an increase in the lengths of the EO chains is shown to decrease the resistance of the transition interface layer at the pristine electrode surface. Second, an ionic transfer study of the electrode surface after electrochemical reactions showed that the polymer electrolytes have a greater effect on the interface transition layers than did the carbonate electrolytes. In addition, a continuity phase including a chemical membrane that is formed from carbonate electrolytes during electrochemical reactions and the enhancing ionic transfer benefits is found by this new detecting methodology.

Definition of ionic transfer mechanisms based on positron annihilation studies in lithium batteries

Abstract An interface ionic transfer detection method called the Doppler broadening S parameter of positron annihilation spectroscopy (PAS) is used to study polysiloxane solid electrolytes with ethylene oxide (EO) side chains and carbonate liquid electrolytes. First, the solid polymer electrolytes are modified to enhance contact with an acrylate, and an increase in the lengths of the EO chains is shown to decrease the resistance of the transition interface layer on a pristine electrode surface. Second, a study of ionic transfer on the electrode surface after electrochemical reactions showed that the solid polymer electrolytes have a greater effect on the interface transition layers than the carbonate liquid electrolytes. In addition, the detection technique revealed a continuous-phase interface containing a chemical membrane formed from carbonate liquid electrolytes by electrochemical reactions; the ionic transfer enhancement due to this membrane is examined by this new detecting methodology.

Large eddy simulation of a shocked gas cylinder instability induced turbulence

The Navier-Stokes equations for compressible fluid are solved with the operator splitting technique and LES (large eddy simulation) with the Smagorinsky model. A computational code MVFT (multi-viscosity-fluid and turbulence) is developed to study hydrodynamic instability and the induced turbulent mixing for multi compressible fluid. In order to validate the code MVFT, the LANL’s shock tube experiment of shocked SF6 gas cylinder is simulated with the initial state of SF6 gas cylinder described by dissipative ITL (interface transition layer). It is shown that the width and height of gas cylinder calculated with MVFT are closer to the experimental results than RAGE, and that the velocities of upstream edge, downstream edge and vortex edge agree with the experimental results, and are appreciably smaller than the RAGE results. The code MVFT has been preliminarily validated.

Stability-instability transition of reaction fronts in thermal oxidation of silicon

By combining atomic force microscopy and x-ray reflectivity measurements, the morphological evolution at the ${\text{SiO}}_{2}/\text{Si}(001)$ interface during thermal silicon oxidation was systematically studied as a function of oxidation temperatures. We found that the oxidation-induced roughening switches to smoothening at an oxidation temperature of $1250\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$ on the oxidation front. The transition is governed by how the strain induced by oxidation is spatially relieved at the interfaces in the silicon oxide bulk film through the interfacial transition layers, which is inevitably important for the strain-relief mechanism.

Silicon Oxide Gate Dielectric on n-Type 4H–SiC Prepared by Low Thermal Budget Anodization Method

Metal-oxide-semiconductor (MOS) capacitors with silicon oxide as the gate dielectric were fabricated on n-type 4H–SiC. was prepared by the room-temperature anodization (ANO) method followed by rapid thermal annealing. Thin oxide layers were produced with various ANO time. The interfacial transition layer is not observed in this work. The oxide breakdown strengths are greater than 5 MV/cm and the capacitance–voltage hysteresis is negligible. Furthermore, the conduction mechanisms in positively and negatively biased regions are explored by the temperature responses of MOS capacitors. For the positively biased case, the conduction mechanism is shown to be dominated by Schottky emission with an effective barrier height of . For the negatively biased case, the gate current is shown to be mainly due to the generation–recombination process in the depletion region. The integration of on n-type 4H–SiC by a low thermal budget process is therefore possible.

SnO 2/ZnO double-layer thin films: A novel economical preparation and investigation of sensitivity and stability of double-layer gas sensors

A double-layer SnO 2/ZnO gas sensor was produced by utilization of SnO 2 and ZnO thin films. Top layer consisted of SnO 2 produced by a sol–gel controlled-annealing technique. Bottom coating consisted of ZnO thin film precipitated by two-stage chemical deposition (TSCD) from an aqueous zinc containing solution. Both top and bottom coatings were analyzed by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and electron dispersive elemental analysis (EDAX). Auger electron spectroscopy (AES) was also used to investigate the growth of tin oxide films on zinc oxide films and their interface. Gas sensitivity of the SnO 2/ZnO double layer was determined by electrical sheet resistance measurements. Although sensitivity was slightly reduced by double-layer formation, selectivity and stability were considerably improved by combination of the two thin layers. The existence of an interfacial transition layer between SnO 2 and ZnO and stabilization mechanism of the SnO 2/ZnO double layer were rigorously investigated in this research.