“Gelios” compact atomic-absorption spectrometer with flame-free atomizer

The principle of operation and specifications of the “GELIOS” atomic-absorption spectrometer with a flame-free (tungsten) atomizer are described. Operation of the device under conditions of pulsed atomization and automatic control of the coil temperature is discussed. A distinctive feature of the device is use of a personal computer to control the coil temperature. Information on the software, test maintenance, reliability, and repairability of the spectrometer is provided. Belarusian State University, 4, F. Skorina Ave., Minsk, 220050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 604–607, July–August, 1998.     

3 to 15 keV Ar+ induced Auger electron emission from Si and Ar

Ar⁺ induced Auger electrons from Si and Ar were investigated at bombardment energies between 3–15 keV and target currents of a few μA. The Auger electron yields were compared with secondary ion yields of Si and Ar by simultaneous SIMS-AES measurements. In the ion induced Auger spectra of Si five Auger peaks and in the Ar spectra three Auger peaks were observed. The ion induced Auger electron yield of Si and Ar were found to be strongly dependent upon the primary ion energy. “Bulk like” and “atomic like” Auger transitions of ion induced Auger electrons of Si were observed.     

AlGaInP visible quantum well lasers for information technology

650 nm-range AlGaInP multi-quantum well (MQW) laser diodes grown by low pressure metal organic chemical vapor deposition (LP-MOCVD) have been studied and the results are presented in this paper. Threshold current density of broad area contact laser diodes can be as low as 350 A/cm². Laser diodes with buried-ridge strip waveguide structures were made, threshold currents and differential efficiencies are (22–40) mA and (0.2–0.7) mW/mA, respectively. Typical output power for the laser diodes is 5 mW, maximum output power of 15 mW has been obtained. Their operation temperature can be up to 90°C under power of 5 mW. After operating under 90°C and 5 mW for 72 hrs, the average increments for the threshold currents of the lasers at 25°C and the operation currents at 5 mW (at 25°C) are (2–3) mA and (3–5) mA, respectively. Reliability tests showed that no obvious degradation was observed after 1400 hours of CW operation under 50°C and 2.5 mW. Presented at the 1st Czech-Chinese Workshop “Advanced Materials for Optoelectronics”, Prague, Czech Republic, June 13–17, 1998.     

Fission fragment anisotropies for 19F +209Bi system

The fission fragment angular distributions have been measured for the system ¹⁹F +²⁰⁹Bi over a range of bombarding energies from 88.0 MeV to 125.6 MeV. The measured fission fragment anisotropies are in agreement with the saddle point statistical model calculations in the above energy range. Combining these data with those available for ¹¹B, ¹²C, ¹⁴N, ¹⁶O and ¹⁸O +²⁰⁹Bi, ²⁰⁸Pb systems, it is concluded that the spherical target plus projectile systems behave “normal” from near- to above – barrier energies. This observation is in contrast to the “anomalous” anisotropies exhibited by the deformed actinide target – projectile systems at near – barrier energies. Received: 5 May 1999 / Revised version: 25 July 1999     

Photoinduced self-limited low-temperature growth of ultra-thin silicon-oxide films with water vapor

The growth of ultra-thin (<2 nm) silicon-oxide films was investigated on Si(100):H, Si(111):H, and a-Si:H surfaces in a pure water atmosphere (0.1–10 Pa) at low temperatures of 30–250 °C. Oxidation was induced photochemically by pulsed F₂-laser radiation at 157 nm. The thickness and composition of the growing oxide films were monitored in real time by spectroscopic ellipsometry in the photon energy range of 1.15–4.75 eV. The mechanism of laser-induced silicon oxidation in a H₂O atmosphere is shown to differ fundamentally from the classical Deal–Grove mechanism of thermal oxidation at 900–1200 °C, as well as from the photoinduced low-temperature oxidation in an O₂ atmosphere. In particular, the film thickness essentially does not depend on temperature below 250 °C. A kinetic model is developed for low-temperature silicon oxidation in a H₂O atmosphere. According to this model, the growth is limited at small thicknesses by the oxidation reaction and at larger thicknesses by reactions of the diffusing oxidizing species in the oxide layer. Very good agreement is established between this kinetic model and the ellipsometric measurements and the temperature and pressure dependence of the water oxidation process. PACS 82.65.+r; 07.60.Fs; 81.65.Mq; 82.50.Hp     

Dissociation of PtSi,NiSi and PdGe in presence of Pt,Ni and Pd films,respectively

⁴He⁺ ions backscattering spectrometry and x-ray diffractometry were used to study interactions between PtSi and Pt, NiSi and Ni, PdGe and Pd. Due to the dissociation of the compound the formation of a phase richer in metal was observed to grow at the original compound/metal interface in the temperature range considered, 280–325°C for Pt₂Si, 325°C for Ni₂Si and 180–260°C for Pd₂Ge. The growth kinetics of these new phases (Pt₂Si and Pd₂Ge) follow a parabolic relation between thickness and annealing time. At a given temperature the growth rate of Pt₂Si and Pd₂Ge in compound-metal structure is a factor higher than in the usual semiconductor-metal structure. Partially supported by Consiglio nazionale delle Ricerche (Italy) and by Commission of the European Communities.     

Spectroscopic study of corona-discharge plasma in inert gas mixtures with impurities of water vapor and air

Positive corona discharge in inert gas mixtures with impurities of water vapor and air in small amounts at pressures of 100–300 kPa is studied. Experiments are carried out on a scale model with a system of gas mixture-pumping of the “electric wind” type. Uzhgorod State University, 46, Pidgirna St., Uzhgorod, 294000, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 242–248, March–April, 1997.     

Characteristics of negative corona discharge in the working media of atmospheric-pressure nitrogen lasers

We present the results of investigations of the electrical and optical characteristics of a negative-polarity corona discharge excited in systems of “pins-mesh” and “pins-plane” electrodes in a He/N₂ mixture at atmospheric pressure. In order that such a corona discharge could be applied in systems of electric pumping of the working medium of atmospheric-pressure N₂-lasers, the optimum conditions should be: the total pressure of the mixture ≤150 kPa and the nitrogen pressure ≤5 kPa. Uzhgorod State University, 46, Pidgirna St., Uzhgorod, 290000, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 837–840, November–December, 1997.     

Thermally activated diffusion of magnesium from bioapatite crystals

We have attempted to use heat treatment followed by ultrasonic treatment to separate the apatite from the non-apatite components of bone mineral in samples from different animals. The Mg content and the Ca/P ratio in the temperature range 560°C–720°C in the samples before and after ultrasonic treatment were determined by electron-probe x-ray microanalysis. Furthermore, we used atomic absorption spectrometry to measure the Mg content in powdered bone samples only after annealing and in distilled water, which was the “sonication” medium. We obtained evidence for thermally activated transition of Mg from a structurally bound state to a labile state at 680°C–720°C. At the same temperature, the Ca-deficient apatite is transformed to stoichiometric apatite. The data presented are evidence that crystals of Ca-deficient bioapatite are surrounded by Ca-enriched surface layers. As a result of thermal transformations at 680°C-720°C, all the Mg in the biomineral is found in the non-apatite environment surrounding the crystals and is removed by ultrasonic treatment, while the surface-localized Ca penetrates into the apatite lattice, restoring its stoichiometry. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 3, pp. 385–391, May–June, 2006.     

Instrumental complex and the results of precise measurements of millimeter- and submillimeter-wave propagation in condensed media and the atmosphere

We describe an instrumental complex based on high-Q open Fabry–Perot resonators for the frequency band 36–370 GHz and present original measurement techniques and the latest results of measuring (i) refractive indices and losses of modern high-quality dielectrics for high-power electronics (with prognosis for up to the terahertz band) and general-purpose dielectrics including films, (ii) reflectivities of both antenna reflectors of cryogenic-receiver radiotelescopes and the so-called “hot” antennas for future Mercurian missions, and (iii) the atmospheric absorption for the development of high-precision wave-propagation models including the continuum absorption. The instrumentation and the measurement techniques are intended for studying condensed-media parameters at temperatures 80–900 K and atmospheric parameters at temperatures from −40°C to +60°C and humidities from 0 to 80%.     

Multilayered electrochemical cell for NOx decomposition at moderate temperatures

A new multilayered electrochemical cell for NO_x decomposition was prepared. The cell demonstrated good characteristics at moderate temperatures (350–450 °C) and possessed much higher selectivity with respect to NO_x decomposition than previous one. It was found that the “crossover” process from high selective regime to the normal regime depends on the chemical composition of the catalytic electrode.     

Collisionless damping of surface oscillations and the possibility of its inversion in plasma-like media

We have developed a quantum theory of collisionless damping of surface plasmons under conditions of weak spatial dispersion of the permittivity of the medium and demonstrate the possibility of appearance of their instability as the interface between the media is crossed by a monoenergetic flow of charged particles. Institute of Radiophysics and Electronics of the National Academy of Sciences, Khar’kov, Ukraine; Research and Design Institute “Molniya” of the Ukraine Ministry of Education, Khar'kov, Ukraine. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 6, pp. 735–746, June, 1998.     

Size control of Si nanocrystals by two-step rapid thermal annealing of sputtered Si-rich oxide/SiO2 superlattice

Controllable size of silicon (Si) nanocrystals can be achieved by a two-step rapid thermal annealing technique consisting of rapid annealing at 1000°C in nitrogen ambient and rapid oxidation at 600–800°C of a radio frequency magnetron co-sputtered Si-rich oxide/SiO₂ superlattice structure. The photoluminescence (PL) spectra related to Si nanocrystals were observed in the visible range (600–900 nm). After rapid oxidation, the size of the nanocrystals was reduced and the quality of the Si nanocrystal/SiO₂ interface was improved, resulting in a blue shift and an increase of the PL peak intensity. Finally, annealing in air increases the PL intensity further.     

Ground-state instability in systems of strongly interacting fermions

The stability of a fermion system is analyzed for a model repulsive pair interaction potential. The possibility of different types of restructuring of the Fermi ground state (at sufficiently great coupling constant) is related to the analyticity properties of such potential. In particular, for the screened Coulomb law it is shown that the restructuring cannot be of the Fermi condensation type, known earlier for some exactly solvable models, but instead belongs to the class of topological transitions. A phase diagram constructed for this model in the variables “screening parameter-coupling constant” displays two kinds of topological transitions: a “5/2” kind, similar to the known Lifshitz transitions in metals, and a “2” kind, characteristic for a uniform strongly interacting system. Pis'ma Zh. éksp. Teor. Fiz. 68, No. 12, 893–899 (25 December 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Low-temperature formation of nanocrystalline SiC particles and composite from three-layer Si/C/Si film for the novel enhanced white photoluminescence

In this article, nanocrystalline silicon carbide (nc-SiC) and composite have been synthesized at an annealing temperature as low as 750 °C through the thermal reaction of Si/C/Si multilayers deposited on the Si(100) substrate by ultra-high-vacuum ion beam sputtering (UHV IBS) compared with the conventional thermal formation of crystalline SiC (c-SiC) nanostructures above 1,000 °C. The evolution of microstructure and reaction between C and Si was examined by Raman spectroscopy, Fourier transform infrared spectrometer (FTIR), high-resolution field emission scanning electron microscope (HR-FESEM), and high-resolution transmission electron microscopy. The c-SiC nanoparticles (np-SiC) of around 20–120 nm in diameter appeared on the top and bottom of the three-layer film with a particle density of around 2.63 × 10¹⁰ cm⁻² after 750 °C annealing. The composite of nc-SiC and Si nanocrystals (nc-Si) size below 5 nm embedded in an amorphous SiC (a-SiC) matrix appeared at the interface between the Si and C layers. Efficient thermal energy is the driving force for the formation of nc-SiC and composite through interdiffusion between C and Si. The broad visible photoluminescence (PL) spectrum of 350–750 nm can be obtained from the annealed composite Si/C/Si multilayer and deconvoluted into four bands of blue (~430 nm), green (~500 nm), green–yellow (~550 nm), and orange (~640 nm) emission, corresponding to the emission origins from nc-SiC, sp² carbon clusters, np-SiC, and nc-Si, respectively.     

Lateral field instability and six-wave mixing in a diode laser with broad active area

The electromagnetic field inside a nonlinear active medium of a laser is considered as a system of counterpropagating waves. Such an approach changes radically an earlier studied behavior of the lateral field instability due to self-deformaion (or self-focusing). In our calculations we used an expression for a laser field in the form of two “strong” counterpropagating waves whose complex amplitudes have weak perturbations. Amplitude perturbations of each of the “strong” waves can be presented by two spatial harmonics corresponding to two weak perturbation waves with wave vectors making some tilted angle ±φ with the cavity axis. Thus six waves would participate in the interaction: two counterpropagating strong waves and two pairs of weak waves. Using this approach, we have developed a theory for the propagation of four “weak” perturbation waves in a nonlinear amplifying medium in the presence of two counterpropagating “strong” waves. It is shown that perturbation waves with tilted angle φ⋍0.5–1.2° inside the active region, and respecively, with the side lobes of the far-field pattern at ∼1.7–4°, have the greatest growth increment. These perturbation waves produce lateral intensity modulation with period 10–30 μm for the 0.85 μm lasing wavelength. The appearance of such waves corresponds to the instability threshold of a homogeneous lateral distribution of optical power in a diode laser. The present theory makes it possible to investigate the stability of the homogeneous lateral optical intensity distribution in a diode laser of any design. This allows one to choose a suitable design of a laser with a homogeneous lateral distribution at high radiation power. Translated from Preprint No. 43 (1992) of the Lebedev Physics Institute, Russian Academy of Sciences.     

On the Rb+ and K+ counterdiffusion in single crystals of K(TiO)PO4 -a quasi-one-dimensional superionic conductor

The diffusion behaviour of Rb/K in K(TiO)PO₄ single crystals has been investigated in the temperature range 350 °C – 450 °C in detail. After a contact of the crystals with Rb containing nitrate melts (8 min - 16 h) the degree of ion exchange and the counterdiffusion coefficient are analyzed in relevant cystallographic directions. A simple atomic model is used to explain the anisotropy of diffusion and the activation energy for the Rb/K counterdiffusion. The influence of different size of the “bottle necks” and different jump distances is discussed for some elementary diffusion steps in the structure of KTP. Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996     

The effect of strong electrical field on the conductivity of proton solid electrolytes NaHSO4 and KHSO4

The influence of passing of high voltage pulse discharges through proton solid electrolytes NaHSO₄ and KHSO₄ and corresponding melts on their conductivities has been investigated. We have discovered the phenomenon of high voltage activation of the investigated electrolytes which is seen by a relative increase of the conductivity. This relative conductivity increase Δσ_rel reaches 754 % (at U=2.8 kV and 181°C) and 218 % (at U=2.0 kV and 200°C) for the solid NaHSO₄ and KHSO₄, respectively. For molten NaHSO₄ and KHSO₄ Δσ_rel is considerably higher and reaches 613% (at U=1.4 kV and 207°C) and 572 % (at U=2.2 kV and 232°C), respectively. We established the “memory” effect which was seen in maintaining of the excess conductivity for a long period of time. The process of relaxation of the excess conductivity of these electrolytes has been studied. The relaxation times of the non-equilibrium charge carriers in these electrolytes varies within the range of (1.9–7.8).10⁴s.     

Disorders produced during high-current and high-dose phosphorus ion implantation in silicon

Transmission electron microscopy, optical reflection and channeling effect measurements are employed to investigate disorders in 30 keV, high dose (3×10¹⁶ions/cm²) and high current (≦5 mA) phosphorus as-implanted silicon with (111), (100), and (110) orientation as a function of temperature rise (100–850°C) by the beam heating effect during implantation. Temperature rise below 400°C results in continuous amorrphous layer formation. This contrasts with results of the recovery into single crystals for temperature rise samples above 500°C, regardless of wafer orientation. Secondary defects (black-dotted defects, dislocation loops and rodlike defects) are formed in singlecrystal recovery samples, having a deeper distribution in (110) wafers and a shallower distribution in (111) and (100) wafers. Rodlike defects observed in 850°C samples are of “vacancy” type and have the largest density in (110) wafers.     

About ionic conductivity/diffusion relationships in yttria doped zirconia

The values of the oxygen self-diffusion coefficients (measured using¹⁸O tracer) are compared to the ionic conductivity (measured by impedance spectroscopy) of 9.5 mol% yttria doped zirconia single crystals in the temperature range 240–800 °C in air. Electrical conductivity measurements in polycrystals, exhibiting a grain boundary contribution to the ionic conductivity, are furthermore discussed in the frame of a “brick/boundary model”. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001.