A study of the infrared spectra of carbon monoxide adsorbed on metals of the copper subgroup and on cobalt,ruthenium, rhodium,and palladium

A study has been made of the infrared spectra of carbon monoxide CO, adsorbed on Cu, Ag, Au, Co, Ru, Rh and Pd at temperatures from –160° C to 200° C and pressures from 10^–5 to 1–10 mm Hg. The spectra of CO adsorbed on Cu, Ag, and Au show one absorption band, characteristic of a surface compound of carbon monoxide, with linear structure. It has been found that in the stable chemosorption of CO on Co, Ru, Rh, and Pd in the range of temperatures and pressures studied, two types of surface compound-linear and bridged-are produced.     

Q band interferometer for high temperature measurements

A Q band interferometer for determining the complex permittivity of solids and liquids between 20°C and 1300°C has been developed. The Roberts and Von Hippel standing-wave method was used. The technique involves the utilization of a computer-assisted digital voltmeter for data acquisition and treatment. Results for a 67SiO₂–33Na₂O within the temperature range 20–400°C and in the liqid state (950°C) are presented.     

Tunneling Processes and Anomalous Fading in Natural Feldspars Extracted from Quaternary Deposits

Reasons for a temporal decrease (fading) in the accumulated energy in feldspars used as paleodosimeters are considered. The tunneling processes capable of leading to fading as well as temperature and time dependences of tunnel afterglow have been studied in detail. It is shown that this glow bears no direct relation to the possible tunnel depletion of the dosimetric trapping centers. With a view toward directly observing tunneling from these centers, the temperature dependences (from −200°C to +100°C) of the intensity of the luminescence stimulated in the IR band with λ ≈ 900 nm (of the optically stimulated luminescence (OSL) signal) have been studied in detail. Within the limits of sensitivity of the equipment used, tunneling from the dosimetric centers has not been detected. It has been inferred that in fading of the OSL signal, an essential role can be played by the traps that are depleted at 200°C and have a lifetime of about 2 years at room temperature.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 2, pp. 207–212, March–April, 2005.     

Elastic properties of NaxK1-xBr and Naxk1-xCl solid solutions

A pulsed ultrasonic method has been used to measure the speeds of longitudinal and transverse elastic waves along [100] and [110] in single crystals of Na_xK_1-xBr and Na_xK_1–xCl solid solutions in the range 20–180°C; the elastic constants c_ik have been determined. These values have been extrapolated to 0°K, while the bulk modulus and shear modulus have been calculated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 76–81, January, 1973.     

Low-temperature diffusion of phosphorus in silicon

Nontrivial mechanisms of low-temperature diffusion of impurities in solids have been discovered recently. We studied accelerated diffusion of phosphorus in a single crystal of silicon, which takes place during decomposition of an over-saturated inhomogeneous solid solution. A thin (1.5–2 m) doped layer was formed by low-temperature diffusion from the gas phase. The distribution profile, which was determined by the method of differential conductivity, shows that heat treatment at 550°C leads to a decrease in the donor concentration in the subsurface region and to the impurity movement into the bulk of the sample. The diffusion coefficient has been calculated on the computer using experimental data, and in the range between 400°C and 700°C has been represented by the Arrhenius equation. The value of the frequency term is equal to 3.7·10^–6 cm²/sec, and the value of the activation energy is 1.81 eV. The presented results have been analyzed, as well as the data obtained from the measurements on carrier mobility (using the Hall effect) and the parameters of the crystal lattice (using the method of asymmetric double crystal x-ray spectrometer). A physical model for the dissociation diffusion is proposed, which is controlled by the decay, and analytical expressions are obtained which describe the main characteristics of the process.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 56–60, September, 1988.     

Annealing behaviour of high-dose-implanted nitrogen in InP

Concentration profiles of nitrogen in vacuum-annealed p- and n-type single-crystal (1 0 0) InP implanted with 1 × 10¹⁶ 30 keV¹⁵N⁺ ions cm^–2 have been studied by Secondary Ion Mass Spectrometry (SIMS) and Nuclear Resonance Broadening (NRB) techniques. Damage induced by the nitrogen implantation was studied by Rutherford Backscattering Spectrometry (RBS) and channeling. Annealing the samples led to loss and redistribution of nitrogen in the temperature range from 575 to 675 °C. At temperatures from 575 to 600 °C, rapid migration of nitrogen towards the sample surface was observed. The n-type InP material had a very dominant tendency for surface nitrogen build-up, whereas the p-type material had a markedly smaller surface peak in the nitrogen distribution. The surface peak in n-type material is due to sulphur acting partly as a diffusion barrier. SIMS analyses showed sulphur build-up on the surface in the course of annealing. At temperatures from 600 to 675 °C, the nitrogen profiles of n- and p-type InP were similar. A small loss of nitrogen was observed at 625–675 °C. Two different recovery stages were observed at 575–600°C and at 625–650 °C. The corresponding activation energies for nitrogen loss are 2.9 and 3.0 eV, respectively.     

Vibrational spectroscopy and the intermolecular dynamics of condensed states V. Temperature dependence of intermolecular spectra of acetonitrile and benzonitrile

Intermolecular spectra are reported for acetonitrile and benzonitrile between –196 °C and 100–140 °C. Structural changes can be established from the integral intensity, peak frequencies, and effective molecular vibration frequencies. There is a polymorphic transition in crystalline acetonitrile between –50 and –60 °C, while there is a change in the structure of liquid benzonitrile in the range 0–10 °C. There are peaks in the intermolecular spectrum of benzonitrile in the liquid state.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 92–95, August, 1971.     

Bulk and near-surface annealing behavior of the 0.8 eV luminescence in semi-insulating gallium arsenide

An annealing study of the 0.8 eV photoluminescence band in LEC GaAs has been performed, using a combination of 10 min annealing steps over a temperature range of 800–1100° C and one hour furnace annealing steps at 500–700° C. Results show that the defect responsible for the luminescence is stable in bulk material under all annealing conditions that have been investigated. In combination with earlier results, this demonstrates a stability of the defect to temperatures in excess of 900° C and indicates a parallel with the annealing behavior of the 0.67 eV band in semi-insulating GaAs. The observed annealing behavior is very different in the near-surface region, indicating an important role of As out-diffusion.     

Comparative study of pulsed laser deposited HfO2 and Hf–aluminate films for high-k gate dielectric applications

The thermal stability and the electrical properties of HfO₂ and Hf–aluminate films prepared by the pulsed laser deposition technique have been investigated by X-ray diffraction, differential thermal analysis, capacitance–voltage correlation, leakage-current measurements and high-resolution transmission electron microscopy observation, respectively. A crystallization transformation from HfO₂ amorphous phase to polycrystalline monoclinic structure occurs at about 500 °C. In contrast, the amorphous structure of Hf–aluminate films remains stable at higher temperatures up to 900 °C. Rapid thermal annealing at 1000 °C for 3 min leads to a phase separation in Hf–aluminate films. Tetragonal HfO₂(111) is predominant, and Al₂O₃ separates from Hf–aluminate and is still in the amorphous state. The dielectric constant of amorphous HfO₂ and Hf–aluminate films was determined to be about 26 and 16.6, respectively, by measuring a Pt/dielectric film/Pt capacitor structure. A very small equivalent oxide thickness (EOT) value of 0.74 nm for a 3-nm physical thickness Hf–aluminate film on a n-Si substrate with a leakage current of 0.17 A/cm² at 1-V gate voltage was obtained. The interface at Hf–aluminate/Si is atomically sharp, while a thick interface layer exists between the HfO₂ film and the Si substrate, which makes it difficult to obtain an EOT of less than 1 nm. PACS 77.55.+f; 81.15.Fg; 73.40.Qv     

Positron states between positronium and “free positron” states in condensed matter

Positronium (Ps), the bound state of an electron and a positron, is formed in many insulating solids and liquids. Recently, several cases of a transition from a Ps state to a non-Ps state have been observed. This has been found for liquid CS₂ if the temperature is decreased from about –40 °C to the melting point, –110.8 °C. In some solid aromatic hydrocarbons, such as naphthalene, biphenyl and p-terphenyl, similar transitions occur upon decreasing the temperature. These transitions are unique in physics since Ps is the only bound state of two light particles in normal low-energy physics. Measurements of the positron lifetime, angular correlation of the annihilation radiation, Ps chemical reactions, and Zeeman effect of Ps give information on the transitions.Deceased.     

Structural relaxation in polyethylene in the presence of silver oxide investigated by positron-lifetime spectroscopy

Structural relaxation in high-density virgin polyethylene and silver oxide doped polyethylene has been investigated using positron annihilation lifetime technique at 30 °C and 100 °C ageing temperatures. The ortho-positronium (o-Ps) pick-off lifetime and its intensity show no changes with isothermal ageing time for the virgin sample at 30 °C. In the case of the doped sample at 30 °C, the o-Ps intensity shows exponential relaxation in the short-time range. At 100 °C, the o-Ps lifetime remains almost constant, whereas the o-Ps intensity exhibits an exponential character in the virgin and doped samples, which can be fitted with exponential decay curves. The relaxation times have been evaluated from the structural relaxation function constructed using o-Ps intensity values, and the stretching exponent has been estimated using the Kohlrausch–Williams–Watts (KWW) function. Positron results indicate that the stretching exponent seems to be temperature dependent. PACS 78.70.Bj     

Gas-phase Crystallization of Titanium Dioxide Nanoparticles

We have investigated the development of crystal morphology and phase in ultrafine titanium dioxide particles. The particles were produced by a droplet-to-particle method starting from propanolic titanium tetraisopropoxide solution, and calcined in a vertical aerosol reactor in air. Mobility size classified 40-nm diameter particles were conveyed to the aerosol reactor to investigate particle size changes at 20–1200°C with 5–1-s residence time. In addition, polydisperse particles were used to study morphology and phase formation by electron microscopy. According to differential mobility analysis, the particle diameter was reduced to 21–23-nm at 600°C and above. Precursor decomposition occurred between 20°C and 500°C. The increased mobility particle size at 700°C and above was observed to coincide with irregular particles at 700°C and 800°C and faceted particles between 900°C and 1200°C, according to transmission electron microscopy. The faceted anatase particles were observed to approach a minimized surface energy by forming {101} and {001} crystallographic surfaces. Anatase phase was observed at 500–1200°C and above 600°C the particles were single crystals. Indications of minor rutile formation were observed at 1200°C. The relatively stable anatase phase vs. temperature is attributed to the defect free structure of the observed particles and a lack of crystal–crystal attachment points.     

The reaction process of the Bi-Sr-Ca-Cu-O system and the forming mechanism of the 2212 superconducting phase

The reaction process and the reaction behavior of each component in the Bi-Sr-Ca-Cu-O system are presented in this paper. It reveals that the reaction is carried out in three different stages: forming of an insulating interphase at 680°C–790°C, forming of the 2212 superconducting phase at 790°C–860°C and forming often semiconducting phases in the presence of the liquid phase at 860°C–970°C. It is also confirmed that the 2212 superconducting phase (T _c=85 K) is formed by the reaction of a trinary interphase together with CuO, SrO and CaO. A new two-step method is presented to prepare the 2212 superconducting phase by a presynthesized interphase.     

Experimental investigation of millimeter wave Gunn oscillator circuits in circular waveguides

Millimeter wave Gunn oscillator circuits using circular waveguides for 33–50 GHz and 75–110 GHz frequency bands are described. These oscillators are simpler to construct at millimeter wavelengths compared to the conventional rectangular waveguide circuits. The effect of various circuit parameters on the oscillator frequency and output power has been experimentally studied. The CW power and mechanical tuning range obtained from the circular waveguide Gunn oscillators are found to be comparable and sometimes even better than those obtained with conventional rectangular waveguide circuits using the same Gunn device.     

Structural phase transition and internal fields in rubidium thiocyanate probed through vibrational spectroscopy

A comprehensive vibrational study of Rubidium thiocyanate (RbNCS), in the 298–448°K range reveals that the orthorhombic to tetragonal transition atT _c440°K is of order-disorder type exhibiting purely second order characteristics. A consistent order-parameter exponent 0.45±0.04 has been obtained from both Raman and IR measurements. In the Raman spectra, the appearance of sidebands in both the C–N&C–S stretching modes and their temperature dependence indicate the existence and a gradual diminution of internal electric field asT approachesT _c. These results have been discussed in the context of an anharmonic oscillator model. An activation energy (U) for the reorientational motion of NCS^– ions,U0.29±0.02 eV, has been calculated from large changes in the bandwidth (_C-N) nearT _c.     

Use of infrared absorption spectra for studying the conformational equilibrium of cis-1-methyl-2-ethylcyclohexane

The equilibrium of the three most stable conformations of cis-1-methyl-2-ethylcyclohexane has been examined on the basis of changes in intensity of the triplet at 585–610 cm^–1 in its infrared absorption spectrum on changing the temperature from 30° to –140° C. H and S have been determined.     

Epitaxy of AlxGa1−xSb films from a molten metal.

Conclusions Crystallization from a solution of antimony in a gallium-aluminum melt has been used to produce epitaxial Al_xGa_1–xSb films with x=0 to 0.4; isothermal (T = 450, 500, 550°C) and isoconcentration (0; 1; 2.4 at. % Al) sections have been drawn for the liquidus surface on the composition plane. X-ray microspectral analysis has been used to examine the composition of the Al_xGa_1–xSb films in relation to aluminum content in the melt, as well as the distribution of Al and Ga over the epitaxial film. These films had a perfect structure. The results enable one to determine the solution composition needed to grow Al_xGa_1–xSb epitaxial films at 450–550°C on gallium antimonide substrates, and it is shown to be possible to make heterostructures in the Al_xGa_1–xSb-GaSb system.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 16, No. 9, pp. 146–148, September.We are indebted to Zh. I. Alferov and V. I. Shveikin for attention and support in this work.     

Thermal hysteresis of permanent magnets of alnico-type alloys

A study is made of the thermal magnetic hysteresis of permanent magnets of the alloy YuNDK25BA in the residually magnetized state with different operating points after two cycles (+20° to 400° to 20°C) and (+20° to –195° to 20°C). The results are interpreted with the model developed earlier by the present authors for thermalhysteretic magnetization reversal in dispersion-hardened alloys. The results can be useful in evaluating the thermal stability of magnets and systems.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizkia, No. 7, pp. 35–38, July, 1979.     

Possible determination of the emission wavelength of active ruby from its temperature. I

The surface-temperature dependence of the emission wavelength has been studied in the range 17–125 °C for two ruby lasers having similar illuminators. The same expression is found for both lasers in the case of identical crystal heating and temperature measurement. We can use this expression to evaluate the wavelength within 0.3 A. The discrepancies between the results obtained and those of other studies are explained.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, Vol. 12, No. 5, pp. 33–36, May, 1969.