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Gerhard Klimeck - One of the best experts on this subject based on the ideXlab platform.

  • full three dimensional quantum transport simulation of atomistic Interface Roughness in silicon nanowire fets
    IEEE Transactions on Electron Devices, 2011
    Co-Authors: Sunggeun Kim, Abhijeet Paul, Mathieu Luisier, Timothy B Boykin, Gerhard Klimeck
    Abstract:

    The influence of Interface Roughness scattering (IRS) on the performances of silicon nanowire (NW) field-effect transistors is numerically investigated using a full 3-D quantum transport simulator based on an atomistic sp3d5s* tight-binding model. An Interface between silicon and silicon dioxide layers is generated in a real-space atomistic representation using an experimentally derived autocovariance function. An oxide layer is modeled in a virtual crystal approximation using fictitious SiO2 atoms. 〈110〉-oriented NWs with different diameters and randomly generated surface configurations are studied. An experimentally observed on-current and threshold voltage are quantitatively captured by the simulation model. The mobility reduction due to IRS is studied through a qualitative comparison of the simulation results with the experimental data.

  • full 3d quantum transport simulation of atomistic Interface Roughness in silicon nanowire fets
    arXiv: Mesoscale and Nanoscale Physics, 2010
    Co-Authors: Sunggeun Kim, Abhijeet Paul, Mathieu Luisier, Timothy B Boykin, Gerhard Klimeck
    Abstract:

    The influence of Interface Roughness scattering (IRS) on the performances of silicon nanowire field-effect transistors (NWFETs) is numerically investigated using a full 3D quantum transport simulator based on the atomistic sp3d5s* tight-binding model. The Interface between the silicon and the silicon dioxide layers is generated in a real-space atomistic representation using an experimentally derived autocovariance function (ACVF). The oxide layer is modeled in the virtual crystal approximation (VCA) using fictitious SiO2 atoms. -oriented nanowires with different diameters and randomly generated surface configurations are studied. The experimentally observed ON-current and the threshold voltage is quantitatively captured by the simulation model. The mobility reduction due to IRS is studied through a qualitative comparison of the simulation results with the experimental results.

  • single and multiband modeling of quantum electron transport through layered semiconductor devices
    Journal of Applied Physics, 1997
    Co-Authors: Roger K Lake, Gerhard Klimeck, Chris R Bowen, Dejan Jovanovic
    Abstract:

    Non-equilibrium Green function theory is formulated to meet the three main challenges of high bias quantum device modeling: self-consistent charging, incoherent and inelastic scattering, and band structure. The theory is written in a general localized orbital basis using the example of the zinc blende lattice. A Dyson equation treatment of the open system boundaries results in a tunneling formula with a generalized Fisher-Lee form for the transmission coefficient that treats injection from emitter continuum states and emitter quasi-bound states on an equal footing. Scattering is then included. Self-energies which include the effects of polar optical phonons, acoustic phonons, alloy fluctuations, Interface Roughness, and ionized dopants are derived. Interface Roughness is modeled as a layer of alloy in which the cations of a given type cluster into islands. Two different treatments of scattering; self-consistent Born and multiple sequential scattering are formulated, described, and analyzed for numerical t...

Ping Xiao - One of the best experts on this subject based on the ideXlab platform.

  • role of internal oxidation on the failure of air plasma sprayed thermal barrier coatings with a double layered bond coat
    Surface & Coatings Technology, 2017
    Co-Authors: Lixia Yang, Xiao Shan, Xiaofeng Zhao, Ping Xiao
    Abstract:

    Abstract Failure of air plasma sprayed (APS) thermal barrier coatings (TBCs) with a double-layered bond coat was investigated. The bond coat consists of a dense layer near the substrate side and a porous layer on the surface. Both were made of NiCoCrAlY alloy and deposited using high velocity oxygen-fuel technique. After thermal cycling, a large amount of internal oxides formed (up to 45% in volume fraction), introducing a significant volume expansion both in in-plane and perpendicular direction in the bond coat. However, the presence of the ceramic top coat can suppress the bond coat in-plane swelling thus lowering the internal oxidation rate. Compared with the fully dense bond coat, the Interface Roughness of the porous bond coat increases significantly when internal oxidation occurs. There is a strong correlation between the internal oxidation and the Interface Roughness. In addition, both the beneficial and detrimental effects of internal oxidation on TBC failure were discussed. It is proposed that a fully dense bond coat with a proper surface Roughness should have a longer thermal cycling lifetime.

Tiejun Wang - One of the best experts on this subject based on the ideXlab platform.

  • the surface cracking behavior in air plasma sprayed thermal barrier coating system incorporating Interface Roughness effect
    Applied Surface Science, 2011
    Co-Authors: Weixu Zhang, Xueling Fan, Tiejun Wang
    Abstract:

    Abstract The objective of this work is to understand the effect of Interface Roughness on the strain energy release rate and surface cracking behavior in air plasma sprayed thermal barrier coating system. This is achieved by a parameter investigation of the interfacial shapes, in which the extended finite element method (XFEM) and periodic boundary condition are used. Predictions for the stress field and driving force of multiple surface cracks in the film/substrate system are presented. It is seen that the Interface Roughness has significant effects on the strain energy release rate, the interfacial stress distribution, and the crack propagation patterns. One can see the completely different distributions of stress and strain energy release rate in the regions of convex and concave asperities of the substrate. Variation of the Interface asperity is responsible for the oscillatory characteristics of strain energy release rate, which can cause the local arrest of surface cracks. It is concluded that artificially created rough Interface can enhance the durability of film/substrate system with multiple cracks.

Claire F. Gmachl - One of the best experts on this subject based on the ideXlab platform.

  • three dimensional Interface Roughness in layered semiconductor structures and its effect on intersubband transitions
    Physical Review B, 2016
    Co-Authors: R Bhat, Alex Y Song, Pierre M Bouzi, Chung En Zah, Claire F. Gmachl
    Abstract:

    A general model for treating the effects of three dimensional Interface Roughness (IFR) in layered semiconductor structures has been derived and experimentally verified. Configurational averaging of the IFR potential produces an effective grading potential in the out-of-plane direction, greatly altering the energy spectrum of the structures. IFR scattering self-energy is also derived for the general case; when IFR is strong, its scattering effect is shown to dominate over phonon interaction and impurity scattering. When applied to intersubband transitions, the theoretical predictions explain the experimental observation of the anomalous energy shift and unusual broadening of the ISB transitions in III-Nitride thin-layered superlattices.

  • importance of Interface Roughness induced intersubband scattering in mid infrared quantum cascade lasers
    Applied Physics Letters, 2012
    Co-Authors: Yenting Chiu, Yamac Dikmelik, Jacob B. Khurgin, Nyan Aung, Claire F. Gmachl
    Abstract:

    The electron transit time of many different quantum cascade lasers has been measured and compared to the calculated upper laser level lifetimes with and without taking into account Interface Roughness induced intersubband scattering. A significantly better correlation is found between the experimental results and the calculation when including the contribution from the Interface Roughness (corr. coeff.: 0.79 vs. 0.43 with and without the consideration of Interface Roughness, respectively). This suggests that in addition to longitudinal optical phonons, Interface Roughness is also crucial in determining the intersubband lifetimes in mid-infrared quantum cascade laser and should routinely be included in design.

  • role of Interface Roughness in the transport and lasing characteristics of quantum cascade lasers
    Quantum Electronics and Laser Science Conference, 2009
    Co-Authors: Jacob B. Khurgin, Kale J. Franz, Anthony J. Hoffman, Matthew D. Escarra, Yamac Dikmelik, Peter Q Liu, Claire F. Gmachl
    Abstract:

    A density-matrix based theory of transport and lasing in quantum-cascade lasers reveals that large disparity between lasing linewidth and tunneling broadening changes the design guidelines to favor strong coupling between injector and upper laser level.

  • role of Interface Roughness in the transport and lasing characteristics of quantum cascade lasers
    Applied Physics Letters, 2009
    Co-Authors: Jacob B. Khurgin, Kale J. Franz, Anthony J. Hoffman, Matthew D. Escarra, Yamac Dikmelik, Peter Q Liu, Claire F. Gmachl
    Abstract:

    A density-matrix based theory of transport and lasing in quantum-cascade lasers reveals that large disparity between luminescent linewidth and broadening of the tunneling transition changes the design guidelines to favor strong coupling between injector and upper laser level. This conclusion is supported by the experimental evidence.

Nicolas Pinel - One of the best experts on this subject based on the ideXlab platform.

  • a modified min norm for time delay and Interface Roughness estimation by ground penetrating radar experimental results
    IEEE Geoscience and Remote Sensing Letters, 2019
    Co-Authors: Meng Sun, Cédric Le Bastard, Yide Wang, Jingjing Pan, Nicolas Pinel
    Abstract:

    The development of methods and tools for the road infrastructure sustainable management is a research challenge, especially for nondestructive testing methods. This letter focuses on the estimation of the thickness of civil engineering structures, like pavements, and more precisely, the time delay and Interface Roughness. We propose a modified Min-Norm algorithm which allows efficiently estimating the time delay and Interface Roughness without the eigenvalue decomposition. Therefore, it has a smaller computational load compared with subspace-based methods. The experimental results show the efficiency of the proposed algorithm.

  • Time Delay and Interface Roughness Estimation Using Modified ESPRIT With Interpolated Spatial Smoothing Technique
    IEEE Transactions on Geoscience and Remote Sensing, 2018
    Co-Authors: Cédric Le Bastard, Yide Wang, Nicolas Pinel, Vincent Baltazart, Jean-michel Simonin, Xavier Dérobert
    Abstract:

    In civil engineering, ground penetrating radar is a common technique for evaluating the structure and quality of road pavement. This paper focuses on the estimation of the time delay and Interface Roughness of civil engineering structure, like pavements. The influence of Interface Roughness is taken into account in the signal model. A modified estimation of signal parameters via rotational invariance technique (ESPRIT) algorithm combined with an interpolated spatial smoothing technique is proposed. It allows us to jointly and efficiently estimate the time delay and Interface Roughness by ultrawideband radar (the upper frequency up to 8-10 GHz) with low computational complexity. The proposed algorithm is tested on both numerical and experimental data. Simulation and experimental results show the good performance of the proposed algorithm.

  • Estimation of time delay and Interface Roughness by GPR using modified MUSIC
    Signal Processing, 2017
    Co-Authors: Meng Sun, Cédric Le Bastard, Yide Wang, Nicolas Pinel, Jingjing Pan
    Abstract:

    In civil engineering, roadway structure evaluation is an important application which can be carried out by ground penetrating radar. In this paper, firstly a signal model taking into account the influence of Interfaces Roughness (surface and interlayer) is proposed. In order to estimate the time delay and Interface Roughness, we propose a method composed of 2 steps: 1) a modified MUSIC algorithm is proposed for time delay estimation; 2) the Interface Roughness is estimated by using Maximum Likelihood method (MLE) with the estimated time delays. The proposed algorithms are tested on data obtained by a method of moments (MoM). Numerical examples are provided to demonstrate the performance of the proposed algorithm.

  • road surface layers geometric parameters estimation by ground penetrating radar using estimation of signal parameters via rotational invariance techniques method
    Iet Radar Sonar and Navigation, 2016
    Co-Authors: Meng Sun, Cédric Le Bastard, Nicolas Pinel, Yide Wang
    Abstract:

    In civil engineering, ground penetrating radar is widely used to assess the roadway structures. This study evaluates the influence of Interface Roughness. A modified estimation of signal parameters by rotational invariance techniques algorithm is proposed with a spectral smoothing technique for efficiently estimating the time delay, the permittivity of the layers and the Interface Roughness. To reduce the impact of noise, a preprocessing method called propagator is used to estimate the noise variance. The algorithm is tested on simulated data obtained by the rigorous numerical method called PILE (propagation inside layer expansion). Numerical simulations are conducted to assess the performance of the algorithm. The simulation results show that the proposed algorithm can estimate road parameters with small relative root mean square error.