Graduation of electron spectrometer intensity scale. Part 2. How to do it

Graduation function G(E′) absolute values have been determined experimentally for the first time for the intensity scale of an ordinary Auger electron spectrometer. The determination of G(E′) includes creation of an original standard signal and measurement of the consequent reaction of the spectrometer using a “giant rectangular modulation” operation mode, integration of the measurand, and use of an original G(E′) definition. The experimental values of G(E′) are presented in the correct dimensional units for a pass energy range E′ = 150–1000 eV. A non-monotonous behaviour of G(E′), a strong dependence of G(E′) on the multiplier entrance bias voltage, and a discrepancy between the graduation functions of spectrometers of the same type with CMA are demonstrated. Possibilities are predicted for a similar G(E′) determination for other types of spectromer.     

Electrical properties of pure and Li2O-doped CuO/Fe2O3 system precalcined at different temperatures

The electrical properties of pure and Li₂O-doped CuO/Fe₂O₃ solids were investigated. Pure and variously doped solids were subjected to thermal treatment at 1073–1273 K and the amount of dopant was varied between 0.84 to 3.36 mol%. The effect of precalcination temperature and amount of Li₂O added on the electrical conductivity σ, activation energy E_a and dielectric constant * were studied. The variation of ′ and ″ as a function of frequency for pure and variously doped solids precalcined at different temperatures was also investigated. The results obtained were discussed.     

Determination and analysis of the dispersive optical constants of the 5,5′,6,6′-tetraphenyl-2,2′-bi([1,3]dithiolo[4,5-b][1,4]dithiinylidene)–DDQ complex thin film

The synthesis and optical properties of the 5,5′,6,6′-tetraphenyl-2,2′-bi([1,3]dithiolo [4,5-b] [1,4]dithiinylidene)–2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) complex thin film were investigated by the optical characterization. The optical constants such as refractive index, extinction coefficient and absorption coefficient were determined using the transmittance T(λ) and reflectance R(λ) spectra and the refractive index dispersion was analyzed using single oscillator of Wemple–Didomenico model. The single oscillator energy E₀ and the dispersion energy E_d were calculated. The effect of temperature on refractive dispersion and optical band gap E_g is also discussed. As a result, the annealing temperatures have an important effect on refractive index of thin film.     

Li-doping effects on the electrical properties of ZnO films prepared by the chemical-bath deposition method

Zn_1−xLi_xO thin films, with x varying from 0.0 to 0.5, successfully have been deposited on glass substrates using the chemical bath deposition (CBD) technique. J–E characteristics, DC conductivity and dielectric measurements have been carried out. These measurements were done as a function of temperature, Li concentration and applied electric field intensity. The J–E characteristics are explained in terms of the Pool–Frenkel and Schottky effects. The J–E relation and DC conductivity are strongly dependent on both the Li concentration and applied electric field intensity. Dielectric hysteresis was observed between heating and cooling runs which revealed that the dielectric constant often increases slowly in the low-temperature region, then increases faster above the phase transition.     

Preliminary results on Cu diffusion through grain boundaries of thin ion-plated Ag---Sn films

The diffusion process of copper through grain boundaries of 500 nm thick ion-plated Ag-12at%Sn films was studied in the temperature range 100–250°C. The method is based on the determination of the time of first appearance of Cu on the Ag---Sn surface using Auger electron spectroscopy for determining trace amounts of Cu. An activation energy of E_a = 0.53 eV and a diffusivity of D′_o = 1.3 × 10⁻⁷cm²s⁻¹ was obtained. For comparison, diffusion studies of Cu through ion-plated pure Ag layers have been performed. In this case an activation energy of E_a = 0.68 eV and a diffusivity of D′_o = 2.3 × 10⁻⁵cm²s⁻¹ have been found.     

Incoherent bremsstrahlung in nuclei

We have studied the processes A(e, e′γ)X in nuclei, or incoherent bremsstrahlung, and determined expressions for the cross section in terms of the same nuclear response functions R_L, R_T, which appear in inclusive electron scattering (e, e′) in nuclei. Calculations of the cross sections are carried out using a Fermi gas model, complemented by the local-density approximation, to evaluate the response functions. We have carried out a study which shows that the reaction can be used to determine reliably the response functions from experimental data. On the other hand we have compared the incoherent bremsstrahlung with the coherent one in order to see the limits to the tagging technique, which produces monochromatic photons based on the assumption of the dominance of the coherent process. We observe that at energies E_γ < 1 GeV the dominance of the coherent process extends to relatively large scattering angles, making the present technique completely safe. However, as the energy of the electron increases, the region of dominance of the coherent process is reduced to smaller scattering angles. These results should be of use when extending the tagging technique to planned or future electron facilities.     

Optical absorption, disorder and the Anderson transition

The optical gap, E_g, of amorphous indium-oxide films is measured as a function of static disorder near the metal-insulator transition. On the insulating side of the transition the optical gap obeys a scaling relation, ΔE_g = -E_*Δg where E_* is of the order of the Fermi energy of the given sample and g≡K_Fl. These results are ascribed to the continuous shift of the mobility-edge in the conduction band with disorder.     

Effect of oxide thickness on the capacitance and conductance characteristics of MOS structures

In this work, the investigation of the interface states density and series resistance from capacitance–voltage (C–V) and conductance–voltage (G–V) characteristics in Au/SnO₂/n-Si (MOS) structures prepared at various SnO₂ layer thicknesses by spray deposition technique have been reported. It is fabricated five samples depending on deposition time. The thicknesses of SnO₂ films obtained from the measurement of the oxide capacitance in the strong accumulation region for MOS Schottky diodes are 37, 79, 274, 401, and 446 Å, for D1, D2, D3, D4, and D5 samples, respectively. The C–V and G–V measurements of Au/SnO₂/n-Si MOS structures are performed in the voltage range from −6 to +10 V and the frequency range from 500 Hz to 10 MHz at room temperature. It is observed that peaks in the forward C–V characteristics appeared because of the series resistance. It has been seen that the value of the series resistance R_s of samples D1 (47 Ω), D2 (64 Ω), D3 (98 Ω), D4 (151 Ω), and D5 (163 Ω) increases with increasing the oxide layer thickness. The interface state density D_it ranges from 2.40×10¹³ cm⁻² eV⁻¹ for D1 sample to 2.73×10¹² cm⁻² eV⁻¹ for D5 sample and increases with increasing the oxide layer thickness.     

Dielectric behavior of hexaferrites BaCo2−xZnxFe16O27

The dielectric constant (′) and dielectric loss (tan δ) for hexaferrites BaCo_2−xZn_xFe₁₆O₂₇ have been studied as a function of frequency (f), temperature (T) and composition (x). The experimental results indicate that ′ and tan δ above the relaxation frequency only decrease as the frequency increases and as the temperature decreases. Tan δ shows the dielectric relaxation at certain critical frequencies which rise as temperature increases. The activation energy for the dielectric relaxation (E_D), ′, and tan δ are found to be minimum for x = 0.8.     

Flat principal bundles over an abelian variety

We prove that a principal G-bundle E_G over a complex abelian variety A, where G is a complex reductive algebraic group, admits a flat holomorphic connection if and only if E_G is isomorphic to all the translations of it by the group structure of A.     

Measurement of the transmission function of the hemispherical energy analyser of ADES 400 electron spectrometer

For determination of the transmission function of a hemispherical energy analyser of an ADES 400 photoelectron spectrometer (V. G. Sci.) a direct method is used. This method is based on the definition of the transmission coefficient of an energy analyser. The number of impinging electrons from an electron gun is measured by a Faraday cup and the current of passed electrons is determined as a peak area of the current signal from the channel multiplier which is used as the Faraday cup. The transmission function of the energy analyser of the ADES 400 photoelectron spectrometer is measured for four values of the analyser pass energy.Presented at the Seminar on Secondary Electrons in Electron Spectroscopy, Microscopy, and Microanalysis, Chlum (The Czech Republic), 21–24 September, 1993.     

Scale-dependent analysis of magnetic flux condensation in QCD

The structure of the vacuum is studied in the Yang-Mills theory as a function of the scale length R. As a candidate of the vacuum we analyze explicitly the Savvidy state. We obtain the following results: (i) there is no gluon condensation for R<R′_c (perturbative phase); (ii) there is condensation of a uniform magnetic flux for R′_c<R<R′_c (Savvidy phase); (iii) the Savvidy state becomes unstable for R>R_c (Copenhagen phase). Here, R_c and R′_c are calculable in terms of magnetic flux condensation H².     

The Boltzmann equation for very hard particles

The nonlinear Boltzmann equation is solved analytically for general initial distributions in a (spatially homogeneous) system of very hard particles (VHP) with two translational degrees of freedom and with a transition probability for binary collisions (vw →v′w′) proportional to δ(v² + w² − v′² −w′²).

The scattering cross-section corresponding to this model increases as the square root of the collision energy (hence the name VHP-model). As the total energy of the system is finite, essentially no highly energetic particles are present to probe the unphysical high-energy behavior of the cross-section.

The VHP-model is extended to a multicomponent mixture of particles, and solved by the same technique, viz. Laplace transformation. An analogous discrete variable model is solved by a generating function method.

Finally the solutions of the nonlinear and linearized Boltzmann equation are compared. Their large-energy behavior at a fixed (large) time is different; their large-time behavior at a fixed energy is the same.     

Metal-clad graded-index planar optical waveguides: accurate perturbation analysis

We present a perturbation analysis of propagation constants and attenuation coefficients of TE and TM modes in a metal-clad linear index planar optical waveguide. The imaginary part N″ of the complex modal index N=N′ + iN″ is given by N″ = (∂N′ / ∂′), where =′ + i″ is the complex dielectric constant of the metal cladding and ∂N′ / ∂′ is obtained by numerical differentiation of the solution of the real eigenvalue equation. The cumbersome solution of a complex transcendental equation is thus completely eliminated. The results are in good agreement with those obtained by solving the eigenvalue equation in the complex plane. By taking the metal-clad linear planar waveguide as a preselected waveguide, we can use our RWKB method to solve metal-clad planar waveguides with parabolic, exponential, gaussian and complementary error function index profiles.     

B→ηlν decays and the flavor-singlet form factors

We study semileptonic decays B→η^(′)lν, taking into account the flavor-singlet contribution (F^singlet₊) to the B→η^(′) form factors, which arises from the two-gluon emission in a decaying B meson. It has been recently pointed out that, in addition to large weak annihilation effects, the unknown value of F^singlet₊ prevents accurate theoretical estimates in the analysis of B→η′K decays in QCD factorization. We present a certain method to determine F^singlet₊ with a reasonable accuracy, using B→η^(′)lν and B→πlν decays. We also investigate the possible effect of F^singlet₊ on the estimated branching ratios (BRs) for B→η^(′)lν and find that the BR for B→η′lν is particularly sensitive to the effect of F^singlet₊.     

Analysis of frequency-dependent series resistance and interface states of In/SiO2/p-Si (MIS) structures

In this work, the investigation of the interface state density and series resistance from capacitance–voltage (C–V) and conductance–voltage (G/ω−V) characteristics in In/SiO₂/p-Si metal–insulator–semiconductor (MIS) structures with thin interfacial insulator layer have been reported. The thickness of SiO₂ film obtained from the measurement of the oxide capacitance corrected for series resistance in the strong accumulation region is 220 Å. The forward and reverse bias C–V and G/ω−V characteristics of MIS structures have been studied at the frequency range 30 kHz–1 MHz at room temperature. The frequency dispersion in capacitance and conductance can be interpreted in terms of the series resistance (R_s) and interface state density (D_it) values. Both the series resistance R_s and density of interface states D_it are strongly frequency-dependent and decrease with increasing frequency. The distribution profile of R_s–V gives a peak at low frequencies in the depletion region and disappears with increasing frequency. Experimental results show that the interfacial polarization contributes to the improvement of the dielectric properties of In/SiO₂/p-Si MIS structures. The interface state density value of In/SiO₂/p-Si MIS diode calculated at strong accumulation region is 1.11×10¹² eV⁻¹ cm⁻² at 1 MHz. It is found that the calculated value of D_it (≈10¹² eV⁻¹ cm⁻²) is not high enough to pin the Fermi level of the Si substrate disrupting the device operation.     

Effective transfer for singlets formed by hole doping in the high-Tc superconductors

By comparing the exact results of an extended multiband Hubbard Hamiltonian for Cu₂O₇ and Cu₂O₈ clusters to those obtained from an effective single band Hamiltonian, we show that the low energy scale physics is very well described by a t-t′-J model which describes the motion of singlets in an antiferromagnetic background of spins. We obtain values for t, t′ and J for both hole and electron doping and show that these are different. We also study the dispersion relations and density of states within the quasi particle approximation both of which show rather interesting characteristics which could be relevant for high T_c superconductors.     

The quantum mechanics of affine variables

We study the wrapping of N-type IIB Dp-branes on a compact Riemann surface Σ in genus g>1 by means of the Sen–Witten construction, as a superposition of N′-type IIB Dp′-brane/antibrane pairs, with p′>p. A background Neveu–Schwarz field B deforms the commutative C-algebra of functions on Σ to a non-commutative C-algebra. Our construction provides an explicit example of the N′→∞ limit advocated by Bouwknegt-Mathai and Witten in order to deal with twisted K-theory. We provide the necessary elements to formulate M(atrix) theory on this new C-algebra, by explicitly constructing a family of projective C-modules admitting constant-curvature connections. This allows us to define the g>1 analogue of the BPS spectrum of states in g=1, by means of Donaldson’s formulation of the Narasimhan–Seshadri theorem.     

Strangeness production on the nucleon

Results of a tree-level analysis of p(γ, K)Y and e, e′K)Y observables are presented. It is shown that the background diagrams play a predominant role in the p(γ,K)Y reaction dynamics. It is argued that the electro-production p(e,e′K)Y channel can help in further constraining the parameters required for determining the background strength.     

On the pp → ppη(η′) reactions near threshold

The production rate for η′ in pp → ppη′ at rest is calculated in a covariant one boson exchange model, previously applied to study π⁰ and η production in NN collisions. The transition amplitudes for the elementary BN → η′N processes with B being the meson exchanged (B = π, σ, η, , ω and a₀) are taken to be the sum of s- and u-channels with a nucleon in the intermediate states, and an a₀ meson pole in a t-channel. The couplings of the η′ to hadrons are a factor 0.4 weaker than the respective η-hadron couplings, as suggested by a quark model and a singlet-octet mixing angle θ = −23°. The model reproduces near threshold cross sections for the quasielastic processes π⁻p → nη(η′) and pp → ppη(η′) reactions.