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Veres T.,Wigner Research Center for Physics | Sajti S.,Wigner Research Center for Physics | Cser L.,Wigner Research Center for Physics | Balint S.,Institute of Materials and Environmental Chemistry | And 2 more authors.
Journal of Applied Crystallography | Year: 2017

Neutron supermirrors (SMs), the major components of neutron optical devices, are depth-graded d-spacing multilayers of several hundreds to several thousands of bilayers. The interface roughness is a major factor in the reflectivity of multilayers. This influence is especially significant if the number of bilayers is large. In this work, the interface roughness and its correlations were studied in DC-sputtered Ni-Ti neutron supermirrors. Detector scans were carried out to observe off-specular neutron scattering in selected regions of the q space from (increasing bilayer thickness) normal-and (decreasing bilayer thickness) reverse-layer-sequence SMs. In-plane and out-of-plane roughness correlations are manifested in diffuse scatter plateaus and peaks which are interpreted in terms of resonant diffuse scattering. Distorted wave Born approximation simulations quantitatively reproduce the characteristic features of the measured detector scans with reasonable roughness correlation parameters, i.e. in-plane and out-of-plane correlation lengths, common interface roughness, and Hurst parameters. The different character of resonant diffuse scattering from normal-and reverse-layer-sequence SMs is qualitatively explained and systematized using quasi-kinematical considerations in terms of material and SM parameters. The total off-specular intensity of the supermirrors was found to be non-monotonic with respect to the specular reflectivity at the corresponding angle of incidence.Long-range interface roughness correlation in Ni-Ti neutron supermirrors is found to manifest in plateaus and peaks in the diffuse neutron scatter. The features are of resonant character and are strongly dependent on the type of the supermirror structure (slowly increasing or decreasing bilayer thickness). Distorted wave Born approximation calculations yield the statistical parameters of the interface roughness correlations. © International Union of Crystallography, 2017.


Horvath Zs.J.,Óbuda University | Horvath Zs.J.,Hungarian Academy of Sciences | Basa P.,Hungarian Academy of Sciences | Basa P.,Semilab Semiconductor Physics Laboratory Co. | And 6 more authors.
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2013

Charge injection and retention behaviors of metal-nitride-oxide-silicon (MNOS) memory structures with Si or Ge nanocrystals embedded at a depth of 3 nm in the nitride layer were studied. The effect of Si nanocrystals on these properties was opposite in comparison with that of Ge nanocrystals. To understand the origin of these opposite effects, the influence of the oxide thickness and of the depth, size and location of semiconductor nanocrystals has been studied on the charging behavior of MNOS non-volatile memory structures by the calculation of electron and hole tunneling probabilities, and by the simulation of memory window, memory hysteresis and retention behavior. For MNOS structures it is obtained that the presence of nanocrystals enhances the charge injection resulting in better performance, but only for structures with thin tunnel oxide layer (below 3 nm), and if the nanocrystals are located close to the oxide/nitride interface. In the case of very high tunneling probability, i.e., of high tunneling currents the system approaches equilibrium and the memory behavior collapses. There is a narrow range of oxide thickness or depth of nanocrystals, where the charging properties change very fast. Retention exhibits a very sharp dependence on the oxide thickness and on depth of nanocrystals as well. Most part of the experimental results can be explained on the basis of the results of simulations. © 2013 Elsevier B.V. All rights reserved.


Horvath Z.J.,Óbuda University | Horvath Z.J.,Hungarian Academy of Sciences | Basa P.,Hungarian Academy of Sciences | Basa P.,Semilab Semiconductor Physics Laboratory Co. | And 6 more authors.
Applied Surface Science | Year: 2013

The charging behavior of MNS (metal-nitride-silicon) and MNOS (metal-nitride-oxide-silicon) structures containing Si or Ge nanocrystals were studied by capacitance-voltage (C-V) and memory window measurements and by simulation. Both the width of hysteresis of C-V characteristics and the injected charge exhibited exponential dependence on the charging voltage at moderate voltage values, while at high voltages the width of hysteresis of C-V characteristics and the injected charge exhibited saturation. The memory window for reference MNS structure without nanocrystals was wider than that for reference MNOS structures. The presence of nanocrystals enhanced the charging behavior of MNOS structures, but in MNS structures nanocrystals exhibited the opposite effect. The main conclusion is that the presence of nanocrystals or other deep levels close to the Si surface enhances the charge injection properties due to the increased tunneling probability, but nanocrystals or other deep levels located far from the Si surface in the nitride layer do not enhance, but even can degrade the charging behavior by the capture of charge carriers. © 2012 Elsevier B.V.


Wang K.,Zhejiang University | Cheng B.,Zhejiang University | Wu B.,Semilab China Co. | Defranoux C.,Semilab Semiconductor Physics Laboratory Co. | And 4 more authors.
Thin Solid Films | Year: 2014

A non-destructive approach to investigate the annealing effects on the optical and electrical properties of SnO2:F/SiCxOy low emissivity (Low-E) films via spectroscopic ellipsometry has been established. Using a four-layer model for the SnO2:F/SiCxOy films with various annealing times at 600 °C, the structural parameters and optical constants were evaluated, presenting an insight to the mechanisms in the deterioration of Low-E performance during annealing. The ellipsometric-derived results show that the roughness layer is decreasing when heating at 600 °C and supposed to give rise to defects and strain variations, contributing to decreased conductivity. However, the diffusion sodium ions from the substrate contribute little to the deterioration of electrical properties during annealing. More intuitively, two key parameters involved in the Drude dispersion law, plasma frequency and collision frequency, were also carried out to evaluate the electrical properties of SnO2:F, and one modified semi-empirical equation is proposed to relate the Drude parameters to emissivity. © 2013 Elsevier B.V. All rights reserved.


Talagrand C.,Ecole Nationale Superieure des Mines de Saint - Etienne CMP | Boddaert X.,Ecole Nationale Superieure des Mines de Saint - Etienne CMP | Selmeczi D.G.,Semilab Semiconductor Physics Laboratory Co. | Defranoux C.,Semilab Semiconductor Physics Laboratory Co. | Collot P.,Arts et Metiers ParisTech
Thin Solid Films | Year: 2015

This paper reports on an InGaZnO optical study by spectrometric ellipsometry. First of all, the fitting results of different models and different structures are analysed to choose the most appropriate model. The Tauc-Lorentz model is suitable for thickness measurements but a more complex model allows the refractive index and extinction coefficient to be extracted more accurately. Secondly, different InGaZnO process depositions are carried out in order to investigate stability, influence of deposition time and uniformity. Films present satisfactory optical stability over time. InGaZnO optical property evolution as a function of deposition time is related to an increase in temperature. To understand the behaviour of uniformity, mapping measurements are correlated to thin film resistivity. Results show that temperature and resputtering are the two phenomena that affect IGZO uniformity. © 2015 Elsevier B.V.


Everaert J.L.,IMEC | Rosseel E.,IMEC | Dekoster J.,IMEC | Pap A.,Semilab Semiconductor Physics Laboratory Co. | And 3 more authors.
Applied Physics Letters | Year: 2010

A method is described to determine the mobility of inversion charge carriers on Si substrates with SiO2 and HfO2 gate dielectrics. It is a completely contactless method combining corona charge and charge spreading metrology. [Patent Application Nos. EP 07118673 and U.S. 60940594.] It is shown that from such measurements mobility of inversion charge carriers can be calculated as a function of the effective electric field. The resulting mobility curves are comparable to those found in transistors. © 2010 American Institute of Physics.


Khosroabadi A.A.,University of Arizona | Gangopadhyay P.,University of Arizona | Cocilovo B.,University of Arizona | Makai L.,Semilab Semiconductor Physics Laboratory Co. | And 4 more authors.
Optics Letters | Year: 2013

The effective medium approximation is used to determine the optical constants of novel silver (Ag)/indium-tin oxide (ITO) multilayer nanopillar structures within the 300-800 nm wavelength range. The structures are modeled as inclusions in air with the pillar volume fraction at 42.4%, agreeing with SEM images of the sample. The simulated reflection intensity of the nanopillars is much less than that of the planar reference sample and is a result of the small difference between the refractive index of the top effective medium layer and that of air. Furthermore, the minimum in the reflection at around 450 nm in the nanostructured sample is evidence of surface plasmon enhancement, indicating suitability for plasmonic applications. The simulated Brewster angle decreases in the pillar region, which is an indication of smaller effective refractive index. © 2013 Optical Society of America.


Csordas A.,HAS ELTE Statistical and Biological Physics Research Group | Csordas A.,Eötvös Loránd University | Almasy O.,Eötvös Loránd University | Almasy O.,Semilab Semiconductor Physics Laboratory Co. | And 2 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

Two species superfluid Fermi gas is investigated on the BCS side up to the Feshbach resonance. Using the Greens's function technique gradient corrections are calculated to the generalized Thomas-Fermi theory including Cooper pairing. Their relative magnitude is found to be measured by the small parameter (d/RTF)4, where d is the oscillator length of the trap potential and RTF is the radial extension of the density n in the Thomas-Fermi approximation. In particular, at the Feshbach resonance the universal corrections to the local density approximation are calculated and a universal prefactor κW=7/27 is derived for the von Weizsäcker-type correction κW(2/2m)(2n1 2/n1 2). © 2010 The American Physical Society.


Findlay A.,Semilab SDI LLC | Lagowski J.,Semilab SDI LLC | Wilson M.,Semilab SDI LLC | D'Amico J.,Semilab SDI LLC | And 3 more authors.
Solid State Phenomena | Year: 2014

Recently introduced techniques for whole wafer mapping and imaging create new possibilities for root cause analysis of emitter passivation defects. Inline compatible PL imaging identifies such defects as localized regions with increased emitter saturation current and reduced implied open circuit voltage. Advanced offline evaluation of defective areas can be then performed with multiparameter noncontact measurements capable to establish the role of surface recombination, the interface trap density, or the dielectric charge that controls the field-effect passivation. The relevant novel metrologies are discussed and are illustrated using examples of advanced silicon passivation by dielectric films and by a-Si heterojunction structures. © (2014) Trans Tech Publications, Switzerland.


Tallian M.,Semilab Semiconductor Physics Laboratory Co. | Pap A.,Semilab Semiconductor Physics Laboratory Co. | Kosztka D.,Semilab Semiconductor Physics Laboratory Co. | Pavelka T.,Semilab Semiconductor Physics Laboratory Co.
AIP Conference Proceedings | Year: 2010

Many state-of-the-art techniques are used to create ultra shallow junctions, but they have a common side effect: the potential increase in the leakage current. This can heavily affect device performance, therefore it needs to be monitored carefully. Junction Photovoltage technique is suitable for the purpose. It is proven to work in a wide range of leakage currents, up to extremely high values. © 2010 American Institute of Physics.

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