Structure analysis of the system Hafnium/Silicon by means of X-ray photoelectron spectroscopy and X-ray photoelectron diffraction (XPD)

Due to the ongoing miniaturization of semiconductor devices new gate dielectrics are required for future applications. In this work we investigated hafnium silicide as a pre-system for hafnium oxide, one of the most promising candidates. One of the major problems of HfO₂-films on silicon is the formation of hafnium silicide at the HfO₂/Si interface. Therefore, ultrathin films of the system HfSi on with a systematic varied thickness from 3 to 30 Å were prepared. Measurements were conducted by means of X-ray photoelectron spectroscopy and low energy electron diffraction (LEED). Also full 2π X-ray photoelectron diffraction (XPD) patterns with high spectral resolution were recorded. Against other reports related to thicker films, several heating cycles showed no phase transitions of the ultrathin films. However, above temperatures of an island formation is strongly indicated. The experimental XPD patterns are compared to simulated patterns of model structures. For the first time we present a modification of the C49 structure a possible structure for ultrathin HfSi₂-films on bulk Si. As an outlook possibilities for preparing the system are introduced.     

calculations of p-type δ-doped quantum wells in Si

We present the hole subband structure calculation in single and double p-type δ-doped quantum wells in Si based on the 4×4 Luttinger–Kohn Hamiltonian. The valence band bending and the Γ hole states are calculated within the lines of the Thomas–Fermi–Dirac approximation and the effective mass theory at the Brillouin zone center. The obtained zone center eigenstates are then used to diagonalize the k·p Hamiltonian for non-zero k. The hole subband structure is analyzed as a function of the impurity density and the distance between δ wells. It is shown that the application of a 4×4 model to describe the hole ground state in single p-type δ-doped in Si can be misleading.     

Novel high-K inverse silver oxide phases of , , , and their alloys

The recently reported inverse silver oxide phase of SiO₂ possesses a high dielectric constant as well as lattice constant compatibility to Si. We explore the closely related oxides, GeO₂, SnO₂ with the same inverse silver oxide structure using ab initio density functional theory within the local density approximation (LDA). According to the phonon dispersion curves, both these structures are computed to be unstable. On the other hand, their alloys Si_0.5Ge_0.5O₂, Si_0.5Sn_0.5O₂, and Ge_0.5Sn_0.5O₂ are stable with higher dielectric constants than that of SiO₂ in the same phase. Their first-principles elastic constants, electronic band structures and phonon dispersion curves have been obtained with high precision.     

Partially mode-dependent filtering for discrete-time Markovian jump systems with partly unknown transition probabilities

This paper is concerned with the partially mode-dependent H_∞ filtering problem for discrete-time Markovian jump systems with partly unknown transition probabilities via different techniques, where the unknown elements are estimated. New version of bounded real lemma for discrete-time Markovian jump systems with partly unknown transition probabilities is presented. Based on the obtained criterion and via a stochastic variable satisfying Bernoulli random binary distribution, new H_∞ filter with partially mode-dependent characterization is established in terms of linear matrix inequalities (LMIs). Finally, numerical examples are given to show the effectiveness of the proposed design method.     

Optimization of a parallel distributed detection system using distance measures

In this paper, we use both J-divergence and Bhattacharyya coefficient as distance measures to optimize a parallel distributed detection system consisting of N local detectors and a global decision maker. The optimization is obtained by allowing the thresholds of the local detectors to be functions of the global probability of false alarm. Numerical results for the case of four and six local detectors are obtained. These results indicate the superiority of our approach over those reported in the literature in which the local thresholds were specified without taking the level of global probability of false alarm into account.     

Photonic theory of noise

The paper proposes that 1/f noise in materials and devices under non-equilibrium conditions is of electromagnetic origin rather than being related to charge carriers. For samples represented by simple resistors the analysis shows that the noise is due to the discrete nature of photons constituting the impinging electromagnetic flux from the source feeding the resistor. The paper presents detailed analysis of the external and internal electromagnetic fields of the resistor environment, with appropriate interpretation in terms of discrete photons. From quantum theory photons are known to retain their energy under interactions in linear environments. This property implies a departure from macroscopic electromagnetics in that photons cannot be partially transmitted and partially reflected, a phenomenon requiring appropriate modifications of boundary conditions at the resistor surface. These special demands call for inclusion of a supplementary internal resistor mode, serving as a lossless idler which is active only for matching purposes. At the resistor terminals the impinging photons give rise to excitation of RF current and voltage noise with an exact 1/f frequency distribution, which is in agreement with all available experimental measurements. The paper presents detailed formulae for noise spectral densities under general drive conditions from DC and RF sources of arbitrary internal resistance. The presented theoretical noise formulae have the same form as earlier empirical formulae for 1/f noise. With an RF source at frequency f₀ the analysis predicts noise with 1/|f-f₀| frequency distribution, which is compatible with available experimental observations.     

Using neighborhood-pixels-information and ANFIS for impulsive noise suppression

This paper introduces a novel approach for denoising the images corrupted by impulsive noise (IN) by using a new nonlinear IN suppression filter, entitled k-nearest neighborhood pixels-based Adaptive-Fuzzy Filter (k-AFF). The proposed filter is based on statistical impulse detection and nonlinear filtering which uses Adaptive-Network-Based Fuzzy Inference System (ANFIS) as a missed data interpolant over the k-nearest neighbor pixels of the corrupted pixels. The impulse detection is realized by using the well-known Kolmogorov–Smirnov-based goodness-of-fit test, which yields a decision about the impulsivity of each pixel. To demonstrate the capability of k-AFF, extensive simulations were realized revealing that the proposed filter achieves a better performance than the other filters mentioned in this paper in the cases of being effective in noise suppression and detail preservation, even when the images are highly corrupted by IN.     

Comment on “closed-form SER expressions for star MQAM in frequency non-selective Rician and Nakagami- channels”

An explicit expression is derived for the symbol error rate (SER) of the star MQAM system considered by Ioannis and Aris [Closed-form SER expressions for star MQAM in frequency non-selective Rician and Nakagami-m channels. Int J Electron Commun AEU 2005;59:417–20].     

Dynamic establishment of restorable connections using -cycle protection in WDM networks

Dynamic establishment of restorable connections in WDM networks is an important problem that has received much study. We propose a dynamic restorable connection establishment scheme that uses p-cycles to protect a connection’s working lightpath. For a given connection request, our scheme first computes a working lightpath and then computes a set of p-cycles to protect the links on the working lightpath so that the connection can survive any single link failure. The key advantage of the proposed scheme is that it enables fast failure recovery while requiring very simple online computation at connection establishment time. Our scheme consists of three components for connection establishment: offline computation of primary cycles, online computation of the working lightpath, and online computation of p-cycles for working lightpath protection. Our scheme also includes a connection teardown procedure that computes and releases all p-cycles that are no longer needed. Simulation study shows that our scheme significantly outperforms an existing p-cycle-based dynamic restorable connection establishment scheme.     

Programmable processor implementations of -best list sphere detector for MIMO receiver

An increasing number of standards in wireless communications have encouraged to study programmable processors as platforms for flexible receivers. A multiple-input multiple-output (MIMO) antenna system combined with orthogonal frequency division multiplexing (OFDM) technique has been introduced in many wireless communications standards, such as in the third generation long term evolution (3G LTE). The MIMO-OFDM system requires an efficient detector and a platform support for parallel processing of multiple subcarriers. A K-best list sphere detector (LSD) provides for near optimal decoding performance and a fixed throughput making it an interesting algorithm from the point of view of practical implementations.In this paper, we compare the implementations of the K-best LSD on four processor platforms: a digital signal processor (DSP), software defined radio (SDR), application-specific processor (ASP) and application-specific instruction-set processor (ASIP). The DSP is a popular very long instruction word (VLIW) device (TMS320C6455), the SDR processor employs multithreading and multiple cores (SB3500 core processor), the ASP is based on transport triggered architecture (TTA), while the ASIP is the SDR processor enhanced with a special instruction-set extension for sorting.A 2×2 MIMO antenna system with 64-quadrature amplitude modulation (64-QAM) is assumed. The chosen list sizes K=8 and 16 are based on simulation results carried out in MATLAB environment with the third generation long term evolution (3G LTE) parameters. The proposed ASIP achieved a promising throughput of 32.0 Mbps, where the software defined radio (SDR) implementation on the SB3500 core processor suffers from an inefficient software sorter. The ASP, in which the minimized hardware complexity has been the goal, achieves a throughput of 7.6 Mbps. However, more essential examination is related to the symbol time, which sets strict parallel processing requirements to the programmable processors.     

Quasi-analytical study of the energy levels in double quantum wells

In this work we develop an analytical expression to the eigenvalue equation for the double quantum well (DQW), to describe the energy gap between resonant levels. The calculation of the energy gap does not involve the evaluation of the wavefunctions for the DQW nor the transfer or tunneling integrals in contrast to how it is usually done.     

Asymptotic bootstrap corrections of AIC for linear regression models

The Akaike information criterion, AIC, and its corrected version, AIC_c are two methods for selecting normal linear regression models. Both criteria were designed as estimators of the expected Kullback–Leibler information between the model generating the data and the approximating candidate model. In this paper, two new corrected variants of AIC are derived for the purpose of small sample linear regression model selection. The proposed variants of AIC are based on asymptotic approximation of bootstrap type estimates of Kullback–Leibler information. These new variants are of particular interest when the use of bootstrap is not really justified in terms of the required calculations. As its the case for AIC_c, these new variants are asymptotically equivalent to AIC. Simulation results which illustrate better performance of the proposed AIC corrections when applied to polynomial regression in comparison to AIC, AIC_c and other criteria are presented. Asymptotic justifications for the proposed criteria are provided in the Appendix.     

Some useful properties of cross--energy operator

In this paper, some useful properties of cross-Ψ_B-energy operator, which measures the interaction between two signals, are provided. We show that Ψ_B is a generalization of some extensions of Teager–Kaiser operator to complex signals. Due to its bilinearity, Ψ_B satisfies the quadratic superposition principle. We point out the link between the Ψ_B and the Lie bracket, which measures the instantaneous differences in the relative change between two signals. We show how the Ψ_B operator can handle wideband signals using bandpass filtering. We also show how the quadratic superposition law can be used for detection purpose.     

The conductance and magnetoresistance effect in a periodically magnetically modulated nanostructure

In this paper, we theoretically investigate the conductance and the magnetoresistance effect in a periodically magnetically modulated two-dimensional electron gas. It is shown that there exists a significant conductance difference for electrons through the parallel and antiparallel magnetization configurations, which leads to a considerable magnetoresistance effect. It is also shown that the conductance and the magnetoresistance effect depend on both the temperature and the number of the periodic magnetic barriers.     

Quantum size effect on excitons in zinc-blende GaN/AlN quantum dot

Within the framework of effective-mass approximation, exciton states confined in zinc-blende GaN/AlN quantum dot (QD) are investigated by means of a variational approach, including three-dimensional confinement of the electron and hole in the QD and finite band offsets. Numerical results show that the exciton binding energy and the interband emission energy are both decreased when QD height (or radius) is increased. Our theoretical results are in agreement with the experimental measurements.     

Growth mechanism of iron nanoparticles on (0 0 0 1) sapphire wafers

Laser ablation of a high purity (99.7%) iron target was used to accomplish the depositions of iron nanoparticles on the (0 0 0 1) face of single crystal sapphire wafers. The nanoparticles were characterized in situ by means of X-ray photoelectron spectroscopy (XPS). The growth mechanism was determined by applying the QUASES-Tougaard methodology to the extended part of the background intensity of the Fe KMM peak in XPS spectra. The heights of nanoparticles obtained are between 3.5 and 6.5 nm. In the first 150 laser pulses, the height of the nanoparticles remained constant while the coverage was increased.     

Piezoelectric models for semiconductor quantum dots

The importance of fully coupled and semi-coupled piezoelectric models for quantum dots are compared. Differences in the strain of around 30% and in the electron energies of up to 30 meV were found possible for GaN/AlN dots.     

Milling time effects on the magnetic and structural properties of the Fe70Si30 system

The magnetic and structural properties of the Fe_0,70Si_0,30 alloy are analyzed by using X-ray diffraction and Mössbauer spectrometry. The samples were prepared by mechanical alloying in a planetary ball mill pulverisette 5 during 1, 5, 9, 15, 75 and 100 h milling, with a ball mass to powder mass relation of 10:1. The X-ray diffraction patterns showed a coexistence of BCC, DO₃ and FeSi structural phases; however, for 1-5 h process, we observed additional peaks which correspond to iron and silicon elements. These results indicate us that the alloy is still a non-fully consolidated sample. The grain size decreases drastically from 1 to 5 h, then slowly up to 15 h, and finally it remains nearly constant. The lattice parameter for each phase remains nearly constant (2838 A for the BCC structure). The shape of hyperfine field distributions used to describe the Mössbauer spectra is discussed.