Fisher Information of Wavefunctions： Classical and Quantum

A parametric quantum mechanical wavefunction naturally induces parametric probability distributions by taking absolute square, and we can consider its classical Fisher information. On the other hand, it also induces parametric rank-one projections which may be viewed as density operators, and we can talk about its quantum Fisher information. Among many versions of quantum Fisher information, there are two prominent ones. The first, defined via a quantum score function, was introduced by Helstrom in 1967 and is well known. The second, defined via the square root of the density operator, has its origin in the skew information introduced by Wigner and Yanase in 1963 and remains relatively unnoticed. This study is devoted to investigating the relationships between the classical Fisher information and these two versions of quantum Fisher information for wavefunctions. It is shown that the two versions of quantum Fisher information differ by a factor 2 and that they dominate the classical Fisher information. The non-coincidence of these two versions of quantum Fisher information may be interpreted as a manifestation of quantum discord. We further calculate the difference between the Helstrom quantum Fisher information and the classical Fisher information, and show that it is precisely the instantaneous phase fluctuation of the wavefunctions.     

Ab initio calculation and analysis of the properties of digital magnetic heterostructures and diluted magnetic semiconductors of IV and III-V groups

We present the first-principles calculations of digital magnetic heterostructures Si/M, Ge/M. GaAs/M, GaSb/M, GaN/M and GaN/M (50%) with M=Cr, Mn, Fe, and Co. The interaction between magnetic dopants results in a wide spin-polarized two-dimensional band inside the gap. It is found that beginning occupation of the minority-spin band greatly increases the energy of the ferromagnetic (FM) state and leads, as a rule, to the antiferromagnetic (AFM) spin ordering. This mechanism causes transition to the AFM state, when interaction between magnetic atoms is too strong, and defines the optimum of Curie temperature as a function of transition element concentration in magnetic layers.     

Electrical and infrared dielectrical properties of silica aerogels and of silica-aerogel-based composites

In this contribution we have studied the key electrical parameters of silica aerogels and of silica-aerogel-based composites, namely the dielectric constants , the dielectric losses tan (at 1 kHz), and the breakdown fields E _b (at 50 Hz). For low-density bulk silica aerogels we find =1.25 and tan =0.0005. E _b is about 500 kV/cm in quasi-homogeneous fields, and of the order of MV/cm in strongly inhomogeneous fields. The dielectric constants of partially densified aerogels increase linearly with density; their dielectric losses are relatively large and their breakdown fields are comparativiely low. The same results are found for aerogels in the form of settled materials, i.e. aerogel granules and powders in air. Acrylate-based aerogel composites with volume fractions larger than 70% have low dielectric constants but their losses are at least 10 times higher than those of low-density aerogels. These materials sustain high local fields in the MV/cm region, while in quasihomogeneous fields, breakdown occurs at about 100 kV/cm. Based on the present results and the interplay with other physical properties (low mechanical resistance, low thermal conductivity, adsorption of water, etc.), silica aerogels and silica aerogel-acrylate-based composites are predicted to have a low potential for electrical insulation.     

Study and applications of plasma-modified Si and porous Si surfaces

In this work we have studied the electrical, chemical and physical properties of CH_x/silicon and CH_x/porous silicon (PS). The hydrocarbon (CH_x) layer has been deposited by plasma of methane under argon atmosphere. Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) Spectroscopy and photoluminescence have been used to characterize the CH_x/p-Si, CH_x/PS interfaces and, electrolyte/(CH_x/p-Si) and CH_x/PS/p-Si structures. The results show that in the case of bare silicon, the CH_x layers act as a resistant film to HF electrolyte and can be used as a potential tool for ultra-low thickness for masking and patterning. The deposition of CH_x layer on PS shows that CH_x/PS/p-Si structure presents a rectifying behaviour and can be used for detecting low concentration of large variety of gases. In addition CH_x coated PS samples exhibit more intense luminescence than that observed from an uncoated PS surface where red luminescence is shown .In conclusion, the results clearly demonstrate the interest and applications of Si and PS electrodes coated with hydrocarbon groups.     

Base doping and dopant profile control of SiGe npn and pnp HBTs

Incorporation of high doping concentrations and the creation and maintaining of steep doping profiles during processing are key enabler for high level RF performance of heterojunction bipolar transistors (HBTs). In this paper, we discuss results of base doping and dopant profile control for npn and pnp SiGe HBTs fabricated within 0.25 μm BiCMOS technologies. High level of electrically active B and P doping concentrations (up to 10²⁰ cm⁻³) have been incorporated into SiGe. By adding C to SiGe steep doping profiles have been maintained due to the prevention of dopant diffusion during device processing. It is shown that broadening of P doping profiles caused by segregation could be reduced by lowering the deposition temperature for the SiGe cap. B and P atomic layer doping is shown to be suitable for the creation of steep and narrow doping profiles. This result is demonstrating the capability of the atomic layer processing approach for future devices with critical requirements of dopant dose and location control.     

Effect of annealing on the electric and magnetic properties of GaMnAs and Be-codoped GaMnAs

GaMnAs and Be-codoped GaMnAs films grown via molecular beam epitaxy (MBE) were heat treated and the stability of Mn in the matrix was investigated. MnAs had a stable phase at the low growth temperature, but MnGa was stable at the annealing temperature. Be-codoping did not prevent the precipitation processes, but Be itself was stable during the annealing process to maintain the GaAs matrix at the high conductivity.     

Influence of temperature and composition on cohesive and thermal properties of mixed crystal manganites

We have investigated the influence of temperature and composition on cohesive and thermal properties of the doped manganites: Eu_1−xY_xMnO₃ (0.0≤x≤1.0) by using a modified rigid ion model (MRIM). Theoretically, MRIM provides arguably the most realistic interaction potential to treat these properties. We have also computed the specific heat variations with temperatures for these manganites. The computed results obtained from MRIM have presented proper interpretation of the experimental data on Eu_1−xY_xMnO₃.     

Comparative examination of the microstructure and high temperature oxidation performance of NiCrBSi flame sprayed and pack cementation coatings

Coatings formed from NiCrBSi powder were deposited by thermal spray and pack cementation processes on low carbon steel. The microstructure and morphology of the coatings were studied by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). Flame sprayed coatings exhibited high porosity and were mechanically bonded to the substrate while pack cementation coatings were more compact and chemically bonded to the substrate. The microhardness and the high temperature oxidation resistance of the coated samples were evaluated by a Vickers microhardness tester and by thermogravimetric measurements (TG), respectively. Pack cementation coatings showed higher hardness and were more protective to high temperature environments than the flame sprayed coatings.     

Nanointegration of ZnO with Si and SiC

The study is dedicated to some aspects of the controlled heteroepitaxial growth of nanoscaled ZnO structures and an investigation of their general and dimension mediated properties. ZnO nanostructures were synthesized by optimized MOCVD process via two growth approaches: (i) catalyst free self-organized growth of ZnO on Si substrates and (ii) ZnO heteroepitaxy on p-type hexagonal 4H-SiC substrates. The SiC substrate was prepared by sublimation epitaxy and served as a template for the ZnO epitaxial growth. The epitaxial growth of n-ZnO on p-SiC resulted in a regular matrix of well-faceted hexagonally shaped ZnO single crystals. The achievement of ZnO integration with Si encompasses controlled growth of vertically oriented nanosized ZnO pillars. The grown structures were characterized by transmission electron microscopy and microphotoluminescence. Low concentration of native defects due to a stoichiometry balance, advanced optical emission, (excitonic type near-band-edge emission and negligible defect related luminescence) and continuous interfaces (epitaxial relationship ZnO_[0 0 0 1]/SiC_[0 0 0 1]) are evidenced. The ZnO nanopillars were further probed as field emitters: the grown structures exhibits advanced field emission properties, which are explained in term of dimensionality and spatial uniformity of the nanopillars. The present results contribute to understanding and resolving growth and device related issues of ZnO as a functional nanostructured material.     

X-ray and neutron reflectivity analysis of thin films and superlattices

X-ray and neutron reflectivity measurements provide a wealth of information on thickness and interfacial properties on the nanometer scale. This method is therefore well suited for the study of nano-structured thin films and superlattices. Neutrons provide a different contrast between the elements than X-rays and, in addition, are sensitive to the magnetization in the sample. Using polarized neutrons, magnetic as well as chemical profiles can be probed. In this review a basic introduction into the theory of X-ray and neutron reflectivity is provided along with some recent examples including the oxidation of Fe films and the structural and magnetic properties of Co/Cu superlattices.     

Direct comparison of the aging and memory effects of magnetic nanoclusters and nanoparticles

The magnetic characteristics of a dense magnetic nanoparticle system and a spin glass system consisting of magnetic nanoclusters are compared. Zero field cooled and field cooled magnetization measurements, including aging and memory experiments, of the nanoparticle and the magnetic cluster systems show similar characteristics, suggesting a common origin for the spin glass-type behavior of the magnetic nanoparticle and nanocluster systems.     

Synthesis and characterization of disodium ethylenediaminetetraacetic acid capped and europium doped CdS nanoparticles

We present a novel two-step chemical synthesis route to produce of disodium ethylenediaminetetraacetic acid (EDTA) capped and europium doped CdS nanoparticles. First EDTA was applied to chelate with cadmium on the surface of cadmium-rich CdS nanoparticles and act as a capping agent. Further, the purified EDTA-capped particles were used to bind with Eu³⁺. The purified and redispersed particles were characterized by UV/vis absorption, photoluminescence, TEM and SEM. It was observed that Eu³⁺ on the nanoparticle surface significantly increased the band gap emission intensity of the CdS nanoparticles.     

Ultrasonic-assisted preparation and characterization of CdS nanoparticles in the presence of a halide-free and low-cost ionic liquid and photocatalytic activity

An ultrasonic-assisted and environmentally favorable method is proposed for preparation of CdS nanoparticles in the presence of a halide-free and low-cost room-temperature ionic liquid (RTIL), 1-ethyl-3-methylimidazolium ethyl sulfate, ([EMIM][EtSO₄]). The prepared samples were characterized by powder X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and Fourier transform-infrared (FT-IR). Diffuse reflectance spectra (DRS) of the products reveal a blue shift of 1.45 eV relative to bulk CdS, which can be attributed to the quantum confinement effect of the prepared nanoparticles. Investigation of photocatalytic activity for the CdS nanoparticles towards photodegradation of methylene blue (MB) demonstrates that photodegradation of MB increases with RTIL content of the media using visible and UV irradiations.     

Identification of a rotator phase of octamethyl ferrocene and correlations between its structural and dynamical properties

The low- and high-temperature phases of octamethyl ferrocene were studied in detail, using high-resolution X-ray powder diffraction, differential scanning calorimetry and nuclear resonant scattering, in particular the novel technique of synchrotron radiation perturbed angular correlations (SRPAC). Much as in the case of an analogous but more unsymmetrical molecule, octamethyl ethinyl ferrocene, the high-temperature phase possesses the space group with lattice parameters , , which in the rhombohedral setting correspond to , α=104.79^°. An increase of the volume per formula unit of about 12% across the phase transition is observed.The rotation of the electric field gradient, which can be identified with the rotation of the entire molecule within the lattice, follows Arrhenius behaviour with a high activation energy of . Whereas precursor effects and a change in activation energy were observed for octamethyl ethinyl ferrocene, no such effects are observed for octamethyl ferrocene. We relate this difference to the absence of the ethinyl substituent in octamethyl ferrocene.     

Integration and characterization of aligned carbon nanotubes on metal/silicon substrates and effects of water

We report here a facile way to grow aligned multi-walled carbon nanotubes (MWCNTs) on various metal (e.g. gold, tungsten, vanadium and copper)/silicon electrically conductive substrates by aerosol-assisted chemical vapor deposition (AACVD). Without using any buffer layers, integration of high quality MWCNTs to the conductive substrates has been achieved by introducing appropriate amount of water vapor into the growth system. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) determination indicate tidy morphology and narrow diameter distribution of the nanotubes as well as promising growth rate suitable for industrial applications. Raman spectra analysis illustrates that the structural order and purity of the nanotubes are significantly improved in the presence of water vapor. The growth mechanism of the nanotubes has been discussed. It is believed that water vapor plays a key role in the catalyst-substrate interaction and nucleation of the carbon nanotubes on the conductive substrates. This synthesis approach is expected to be extended to other catalyst-conductive substrate systems and provide some new insight in the direct integration of carbon nanotubes onto conductive substrates, which promises great potential for applications in electrical interconnects, contacts for field emitters, and other electronic nanodevices.     

Morphological and electronic properties of the thin film phase of pentacene investigated by AFM and STM/STS

We investigated the morphological, structural and electronic properties of Pentacene thin films grown by vacuum thermal evaporation on different inert substrates at room temperature. The results of our AFM and STM analysis give an interplanar spacing of 1.54 nm corresponding to the (0 0 1) distance of the so-called “thin film phase”. The STS measurements show an HOMO-LUMO gap of 2.2 eV.     

Chemical and microstructural study of the oxygen passivation behaviour of nanocrystalline Mg and MgH2

Nanocrystalline Mg and MgH₂ samples have been prepared by high-energy ball milling and gas phase condensation methods. Starting from these materials in their “as received” state without air exposure, a study of the oxygen and air passivation behaviour was carried out by “in situ” analysis of the samples by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The binding energy and photoemission Auger parameters have been determined for metallic magnesium as well as for magnesium hydride, oxide and hydroxide species. Values of the MgH₂ material were reported for the first time. The study clearly shows the formation of an oxide passivation layer of ca. 3-4 nm in thickness for all the nanocrystalline magnesium samples handled under controlled inert gas atmospheres. A hydroxide like amorphous layer is formed at the topmost surface layers of the nanocrystalline Mg and MgH₂ samples. The implication of these studies for H₂ storage and transport applications of nanocrystalline magnesium is discussed.     

Optical and AFM study of electrostatically assembled films of CdS and ZnS colloid nanoparticles

CdS and ZnS semiconducting colloid nanoparticles coated with the organic shell, containing either SO₃⁻ or NH₂⁺ groups, were prepared using the aqueous phase synthesis. The multilayer films of CdS (or ZnS) were deposited onto glass, quartz and silicon substrates using the technique of electrostatic self-assembly. The films produced were characterized with UV-vis spectroscopy, spectroscopic ellipsometry and atomic force microscopy. A substantial blue shift of the main absorption band with respect to the bulk materials was found for both CdS and ZnS films. The Efros equation in the effective mass approximation (EMA) theoretical model allowed the evaluation of the nanoparticle radius of 1.8 nm, which corresponds well to the ellipsometry results. AFM shows the formation of larger aggregates of nanoparticles on solid surfaces.     

Model of opinion forming and voting

A simple model describing the dynamics of opinion forming in a two-party society is presented. Using a Monte Carlo simulation, we show what is the role played by the mobility of the electorate and the size of the groups within which opinions are exchanged. Each individual is characterized by its opinion and its susceptibility to the influence of others. We show what is the effect for a party to have a small percentage of supporters who will never change their mind. We determine when a party having at the beginning a smaller number of supporters, could nevertheless win democratic elections. The influence of an external random field (media) is also discussed.     

Photoablation by UV and visible laser radiation of native and doped biological tissue

Photoablation studies of biological material (human cornea) with UV and visible laser light show that effective, apparently non-conventional thermal photoablation can be achieved by introducing energy absorbing dopants in the tissue. Previously unknown high ablation rates of 80 Gmm/pulse have been observed. The results allow one to clearly postulate different ablation mechanisms for increasing laser fluence. The results are compared with the photoablation rates observed with 193 nm UV laser light on undoped human cornea. Explosive desorption has been found the dominant process involved.