Study of the spectrum of CH3 35C1 between 4250 and 4600 CM−1: thev 2+v 4 andv 4+v 5 rovibrational bands

About 2500 lines of CH₃ ³⁵Cl have been assigned. The strong xy Coriolis resonance between thev ₂ andv ₅ modes is quite visible between thev ₄+v ₄ ^±1 perpendicular band, centered around 4383 cm^?1, and thev ₄ ^±1 +v ₅ ^±1 perpendicular component, centered around 4475 cm^?1, with a crossing of upper energy levels allowing the observation of lines which are normally forbidden. Although not yet observed with certainty, because of the great density of lines of the spectrum, thev ₄ ^?1 +v ₅ ^±1 parallel component is nevertheless detectable by its effects onv ₂+v ₄ ^±1 which is linked by Coriolis resonance to both components ofv ₄+v ₅. Moreover the spectrum is much complicated by many other resonances with weak bands which occur at level crossings: it is the case ofv ₂+3v ₆ ^±1 , connected tov ₂+v ₄ ^±1 by the well known Darling Dennison resonance which couplesv ₄ ^±1 and 3v ₆ ^±1 , and also ofv ₅ ^±1 +3v ₆ ^±1 connected tov ₄ ^±1 +v ₅ ^±1 by the same resonance; but this last case is complicated by an anharmonic resonance betweenv ₅ ^±1 +3v ₆ ^±1 and 2v ₃+3v ₆ ^?1 . Two more perturbations occur on the ΔK=?1 side ofv ₂+v ₄: a weak Coriolis resonance gives rise to one subband ofv ₁+v ₂ at a level crossing withv ₂+v ₄, and thev ₁+v ₅ band (linked of course tov ₁+v ₂ by the Coriolis resonance between thev ₂ andv ₅ modes) is quite visible and perturbs several subbands ofv ₂+v ₄ of high values of K through an anharmonic resonance. Moreover, the complex (3v ₅ ^±1 ,v+2v ₅ ⁰ , 2v ₂+v ₅ ^±1 , 3v ₂,v ₂+2v ₅ ^±2 , 3v ₅ ^±3 ) system of Coriolis-connected bands is linked to the bands studied in the present work by two Fermi resonances: one betweenv ₂+2v ₅ ⁰ andv ₁+v ₂, and the other one betweenv ₁+v ₅ and 3v ₅ ^±1 , whose several subbands have been observed on the low part of the spectrum. The values of all the band centres and of the different coupling constants have been estimated, but all these interactions make the line assignments and the interpretation of the spectrum very difficult.     

I–V characteristics and the spectrum width during electron tunneling through nanosandwiches W-WO2-(Au 147 ? )-Al2O3-Al and Nd-Nd2O3-(Au 55 ? )-Nd2O3-Nd. Part I: Quantum-chemical calculation of energies of orbitals for anions of nanoclusters Au55 and Au147

This work is devoted to the investigation of electron tunneling through ??magical?? nanoclusters Au₅₅ and Au₁₄₇. Using the quantum-chemical calculation, it is shown that the energy of the highest occupied molecular orbital (HOMO) level is ${E_{HOMOAu5{5^ - }}} = - 3.2eV$ and E _HOMOAu147 = ?4.4 eV, respectively. It is established that the difference between energy E _LUMO ^? of the lowest unoccupied level LUMO and energy E _LUMO ^? for the anions of clusters (Au ₅₅ ^? and Au ₁₄₇ ^? ) is 0.86 and 0.24 eV, respectively. Based on the results of the calculations, it is assumed that nanosandwiches W-WO₂-(Au ₁₄₇ ^? )-Al₂O₃-Al can be promising structures for implementation of metal nanodiodes based on them, while nanosandwiches Nd-Nd₂O₃-(Au ₅₅ ^? )-Nd₂O₃-Nd can be promising for implementation of energy filters not producing hot electrons and allowing the fabrication of the ring Aharonov-Bohm interferometers based on normal metals at liquid-helium temperatures.     

Role of silicon vacancies in formation of Schottky barriers at Ag and Au contacts to 3C-and 6H-SiC

A modified Ludeke model assuming that interfacial defect states are responsible for the formation of the Schottky barrier is applied to calculate the barrier heights Φ _b ⁿ in the systems 〈Ag, Au〉-〈3C-, 6H-SiC〉. Excellent agreement with experimental data is obtained. The calculation also shows that the concentration of silicon vacancies determining the Φ _b ⁿ value depends only slightly on the nature of the metal constituent of the contact.     

Effect of nonstoichiometry and doping on the photoconductivity spectra of GeSe layered crystals

The polarization photoconductivity spectra of Bi-doped nonstoichiometric GeSe layered crystals grown by static sublimation were investigated. Two strongly polarized maxima at the photon energies hν_max = 1.35 eV (E ∥ a) and 1.44 eV (E∥ b) due to the V ₁ ^V → V ₁ ^c and Δ ₂ ^v → Δ ₁ ^c optical transitions, respectively, were found in the spectra of nominally undoped GeSe crystals near the intrinsic absorption edge at 293 K. In the low-temperature region, an exciton photoconductivity band peaked at hν_max=1.32 eV, which is due to exciton dissociation at the cation vacancies, was revealed. With an increase in excess Se in crystals, a sharp increase in the intensity of the exciton peak in the photoconductivity spectra was observed. It is shown that doping of GeSe crystals with donor Bi impurity is an effective tool of the control of their electrical and photoelectric properties. Although introduction of Bi into germanium monoselenide does not lead to the conductivity conversion from the p to n type, a sharp increase in the resistivity is observed, the crystals become photosensitive, and a strong impurity band peaked at 1.11 eV arises in the photoconductivity spectra.     

Molecular — impurity absorption in KC1 for infrared laser windows

Residual impurity absorption in the 10μm region severely limits the usefulness of KCl as a high-power CO₂ laser window. In order to investigate possible origins for this absorption, KCl was doped with carbonate and hydroxyl impurities, and grown in various atmospheres. Characteristic absorption bands in the infrared and ultraviolet were used to determine relative dopant concentrations. Growth conditions introducing CO/ ₃ ⁼ exclusively, led to relatively low and featureless absorption spectra in the 10.6μm region, while conditions introducing both CO/ ₃ ⁼ and OH⁻ led to enhanced absorption. (Additionally, a correlation is indicated between the strength of absorption at 10.6μm and that of the oxygen band at 0.26μm in samples grown in atmospheres in which oxygen was present). Our observations suggest the possibility of absorption due to CO/ ₃ ^≽ complexes, NO ₃ ⁻ , HCO ₃ ⁻ and/or ClO ₃ ⁻ in the 10μm region. While the effects of ultralow concentration of these impurities remain uncertain, the present results suggest that their presence may well contribute to extrinsic absorption in the 10μm region. Rsch supported by AFCRL(AFSC) - Contr F19628-72-C-0286     

The contact of metal with silicon carbide: Schottky barrier height in relation to SiC polytype

The results obtained in measuring the Schottky barrier height Φ _b ⁿ for a chromium contact with 8H-, 6H-, 15R-, 27R-and 4H-SiC silicon carbide polytypes with n-type conduction are analyzed in terms of a simple model. It is shown that the Φ _b ⁿ value is proportional to the concentration of silicon vacancies in the polytypes. The results of Φ _b ⁿ measurements for palladium and platinum contacts to silicon carbide polytypes are discussed.     

The nature of point defects in CdTe

High temperature in-situ Hall effect measurements in CdTe single crystals grown by different techniques at 500–1,200 K under well-defined Cd and Te vapor pressure were made. It was established that native point defects (PD) Cd _i ²⁺ and V _Te ²⁺ are dominant at T>770 K in Cd-rich CdTe. Their formation enthalpies were determined (ΔH _VTe ²⁺ =1.3 eV; ΔH _Cdi ²⁺ =2.5 eV). It was shown that V _Te ²⁺ dominate at low temperatures and Cd _i ²⁺ begin to prevail at T>930 K. In Te-saturated CdTe at heating up to ～800 K, the hole density was Te vapor pressure independent. At higher temperatures (HT), the conductivity changed to intrinsic type, turning then into n-type. The results were explained in the framework of Kröger’s quasichemical formalism assuming the presence of an electrically active foreign point defect, the oxygen acceptor. The PD structure modeling demonstrated satisfactory agreement with experimental results both for temperature and component vapor pressure dependencies.     

TE On o -to- mode transducer designmode transducer design

This paper gives a structure on the mode converter from TE _0n ^O mode of gyrotron output to the main mode of the circular groove guide. The design consists of two parts: the first part is to convert TE _0n ^O to TE ₀₁ ^O using an advanced periodic wall perturbation technology, the second part is to convert TE ₀₁ ^O to mode basing on the method of gradually changing the wave guide cross section. An example at 37.5Ghz is given. For the first part, the efficiency is 94.71%, the length is 1.868m. For the second part, the theoretic figure of reflectance coefficient vs. frequency is given.     

(211)-Oriented Domain Formation During Growth of ZnTe on m-Plane Sapphire by MBE

ZnTe epilayers have been grown on 2°-tilted m-plane $\left( {10\overline{1} 0} \right)$ sapphire substrates by molecular beam epitaxy. Pole figure imaging was used to study the domain distribution within the layer, and the pole figures of 111, 220, 004, and 422 ZnTe and $30\overline{3} 0$ sapphire were measured. Computer simulation was used to analyze the symmetry of the diffraction patterns seen in the pole figure images. Stereographic projections were also compared with the pole figures of 422 and 211 ZnTe, confirming that single-domain (211)-oriented ZnTe epilayers had been grown on the 2°-tilted m-plane sapphire substrates. Although differences in crystal structure and lattice mismatch were severe in these heterostructures, precise control of the substrate surface’s lattice arrangement would result in the formation of high-quality epitaxial layers.     

INFLUENCE OF MAGNETIC FIELD INHOMOGENEITY ON OPERATION OF THE THz GYROTRON WITH A PULSE MAGNET

Influence of magnetic field tapering on operation of a gyrotron working in the TE _4,12 mode at the second harmonic frequency 1013.67 GHz is investigated. It is found that the existing inhomogeneity of the magnetic field of the order of 0.25%–0.50% in the cavity allows one to achieve higher efficiencies. It improves also mode competition scenario by suppressing oscillations of the two parasitic TE _3,6 ⁺ and TE _5,5 ^? modes at the fundamental frequencies 513.35 GHz and 503.64 GHz, respectively.     

On measuring the permittivity of “living” wood for microwave remote sensing

A procedure for measuring the permittivity of “living” wood is proposed. The permittivity of the trunk of a growing tree ε ₁ ^* has been measured by this procedure. Simultaneously, samples of wood of the same tree have been taken and their permittivities ε ₀ ^* determined under laboratory conditions. The obtained values has been compared, and considerable disagreement between measured ε ₁ ^* and ε ₀ ^* has been revealed. The study has been performed to model the reflection of microwaves from the forest.     

Analysis and application of NRD-guide excitors

In this paper, the NRD-guide excitors using a length of coaxial line which consists of a rectangle external conductor and a thin round inner conductor are presented, and the characteristics of the input impedances of LSE ₁₁ ^o mode and LSM ₁₁ ^o mode at the insertion points are analysed and calculated by using the method of the rector Green's function respectively. The computation results show that the mode excitors are able to improve the operating modes matching between NRD-guide and the quasi-TEM transmission line. The structures are suitable for fabrication LSE ₁₁ ^o mode oscillator and LSM ₁₁ ^o mode oscillator to compose millimeter wave NRD-guide integrated front ends. An example of an LSE ₁₁ ^o mode oscillator in Ka-band is given. Its oscillation frequency and output power could be easily adjusted by changing the parameters of the excitor.     

Injection currents in amorphous alloys of the Se-S system

The study of current-voltage characteristics of amorphous film samples of the Se_1?x S _x system (x = 0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5) showed that carrier transport occurs by the mechanism of one-carrier injection space-charge-limited currents, involving two groups of traps, i.e., shallow ones (E _t1) corresponding to charged intrinsic defects C ₁ ^? and caused by dangling bonds in selenium and deep traps E _t2 also corresponding to charged intrinsic defects _{C 3} ⁺ in selenium. It has been shown that a change in the Se-S system composition significantly affects both the charge transport mechanism and trap parameters, i.e., energy states and concentrations.     

Electrical characteristics of CdTe:Pb single crystals at high temperatures

The electrical properties of CdTe:Pb single crystals at high temperatures (400–900°C) and under controlled Cd vapor pressure (0.001–3 atm) were investigated for the first time. The temperature and baric dependences of the conductivity and Hall coefficient were measured. Low (in comparison with undoped CdTe) electron concentration indicates an increase in the number of impurity point defects related to the Pb impurity. The results obtained are explained within the Kröger theory of quasi-chemical reactions of defect formation on the assumption that lead may exist in the isolated state (Pb _Cd ⁺ ) and as a component of (Pb _Cd ⁺ V _Cd ^2? )^? associates.     

Investigation of vacancy-type complexes in GaN and AlN using positron annihilation

The momentum distribution of electron-positron pairs in GaN and AlN has been investigated for the first time by measuring the one-dimensional angular correlation of the annihilation radiation (1D-ACAR). The characteristic parameter of the electron density r _s ^′ (the radius of the sphere occupied by an electron) estimated from the experimental data differs noticeably from r _s calculated in terms of a standard model of noninteracting particles: r _s ^′ (AlN)≈1.28r _s, and r _s ^′ (GaN)≈1.66r _s, where r _s(AlN)≈1.6091 au, and r _s(GaN)≈1.6568 au. The chemical nature of atoms in the environment of the annihilating positron in AlN and GaN was identified from the electron-positron ionic radius of Al³⁺, Ga³⁺, and N⁵⁺ cores, which were determined from the characteristics of the high-momentum component of 1D-ACAR curves. The analysis was based on a comparison of the electron-positron ionic radii with those considered standard for Al and Ga metals and the related compounds GaP, GaAs, and GaSb. A conclusion is made that positron annihilation dominates in the regions of vacancy-type “nitrogen antisite”-“vacancy” complexes, [N _Ga ⁺ V _Ga] and [N _Al ⁺ V _Al], in GaN and AlN, respectively.     

Topological size effect in tin-dioxide cluster films produced by reactive sputtering

The optical properties of tin-dioxide nanofilms produced by reactive sputtering are studied by the internal reflection technique and modulation polarimetry. The angular and spectral characteristics of the reflection coefficients R _s ² and R _p ² are studied for linear-polarized radiations, for which the wave electric field is, correspondingly, orthogonal and parallel to the plane of incidence. The characteristics of the physical difference between the reflection coefficients, ρ = R _s ² -R _p ² , are studied as well. From the experimental results, it follows that (i) the doping-induced finite conductivity of the film brings about the appearance of surface plasmon resonance; (ii) the shape of the spectral and angular characteristics of the parameter ρ is indicative of the cluster structure of the film, which is in agreement with the phase topology data obtained by atomic force microscopy; and (iii) the nonspherical shape of the clusters is responsible for the splitting of resonances and for the dependence of their parameters on the angle of incidence, which defines the topological size effect.     

Die Bestimmung der KabelkopplungsparameterZ T ′ undY T ′ und ihr Wert für die EMV-Analyse

In EMC analysis, shielded cables are best characterized by a peculiar set of coupling parameters: the transfer impedanceZ _T ^′ , and the transfer admittanceY _T ^′ or the radial electric coupling coefficient ζ_R. Here, a way is shown how to measure these parameters and two examples are given of applying these parameters in practice.     

Origin of an absorption band peaked at 5560 cm−1 and related to divacancies in Si1−x Gex

It is found that two types of centers are formed in Si_1?x Ge_x single crystals as a result of irradiation with fast electrons: divacancies (V ₂) characteristic of silicon and the V ₂ ^* centers; the latter are complexes of divacancies V ₂ with germanium atoms (V ₂Ge). It is shown that an absorption band peaked at about 5560 cm^?1 is a superposition of two absorption bands that correspond to the above centers. The V ₂ divacancies diffuse during isochronous heat treatment and interact with germanium atoms, thus giving rise to additional V ₂ ^* centers. The latter have a higher thermal stability than the V ₂ centers do, and their annealing temperature increases with increasing content of germanium.     

Long-range effects of ion irradiation, chemical etching, and mechanical grinding on relaxation of a solid solution of iron in gallium phosphide

Electron spin resonance was used to study directly the influence of external factors on a system of defects in gallium phosphide crystals doped nonuniformly with iron. The Fe _s ³⁺ (Ga) ions replacing Ga atoms (the A centers) and Fe _i ⁰ interstitial atoms (the B centers) are considered as indicators and participants in rearrangement of the crystal’s defect system. Long-range effects of ion irradiation with argon, chemical etching, or mechanical grinding on the A and B centers are observed. The long-range effect is explained by plastic deformation of the GaP:Fe crystal and by interaction of dislocations with A and B centers when the crystal is modified by ion irradiation or by removal of a layer that is saturated with Fe _s ³⁺ (Ga) centers and gives rise to stresses from one of the sample surfaces. In the case of ion irradiation, the role of elastic waves that are generated in the stopping zone of argon ions and that interact with B centers and dislocations is apparently important.     

Studies of the infrared luminescence of ZnSe doped with copper and oxygen

The results of studying the poorly understood 700-to 2000-nm spectral region in ZnSe cathodoluminescence of condensates deposited from the vapor phase with deviations from stoichiometry and Cu and O introduction into a pure matrix are reported. The nature of cathodoluminescence in the region of 1300–1400 nm is refined: the conclusion is drawn that the emission is caused by isolated V _Zn ^I(II) vacancies. The behavior of V _Se-related luminescence bands at 830 and 960 nm, when the matrix composition changes, is considered.