Radical-Recombination Luminescence of the Uranyl Nitrate Complex in the Adsorbed State

We have investigated the luminescence of uranyl nitrate molecules on the surface of powdery SiO₂ upon excitation by UV light (PhL) and hydrogen atoms (radical-recombination luminescence (RRL)). It has been found that the PhL and RRL spectra have a clearly defined vibrational structure. The luminescence peaks of the adsorbed UO₂ ^2– ion are characterized by a systematic longwave shift from the same peaks of crystalline uranyl nitrate (by 230–430 cm^–1 at 130 K). Moreover, in the adsorption centers the vibration frequencies of UO₂ ^2– are 20–80 cm smaller than in crystalline salt and the RRL bands are 150–350 cm^–1 (130 K) wider than the corresponding PhL bands.     

Local Vibrations of Oxygen-Containing Thermal Donors in Germanium

The vibrational absorption bands associated with some types of double thermal donors (TD) in Ge enriched with the oxygen isotopes ¹⁶O and ¹⁸O have been identified. The thermal donors were formed during heat treatment of Ge:O crystals at 300 and 350°C. Absorption spectra were measured at room temperature and at 10 K. The formation of the thermal donors was accompanied by the appearance of three absorption bands, which in the Ge:¹⁶O spectra at room temperature are located at 600, 740, and 780 cm^–1. In low-temperature measurements, the bands at 600 and 780 cm^–1 exhibited splitting into series of narrow lines (up to 9) associated with some types of thermal donors (TD1–TD9). The absorption spectra measured at 10 K after different cooling conditions display bistability of the first four types of thermal donors (TD1–TD4). In the samples cooled by illumination with light in the region of frequencies of the fundamental absorption of Ge, pairs of lines are observed that belong to the bistable thermal donors in the helium-like configuration of double donors (DD). After cooling the samples in the dark, these pairs of lines are replaced by three new bands, which belong to local vibrational modes of bistable thermal donors in the low-energy neutral configuration. Based on the isotopic shift of the local vibrational modes of the thermal donors in Ge:¹⁶O and Ge:¹⁸O, a rigorous proof of the oxygen atoms entering into the composition of thermal donors is obtained.     

Absorption coefficient in the wings of carbon dioxide bands in the 790–910-cm−1 spectrum range

The absorption coefficient of carbon dioxide is computed on the basis of the theory of spectral line wings during self-broadening and for broadening by nitrogen in the range 790–910 cm^–1 at 296 and 240°K temperatures. The contribution of the 18 vibrational-rotational bands of CO₂ to absorption is taken into account. The temperature dependence of the absorption coefficient was determined by the dependence of the classical intermolecular interaction on the temperature. The results of the computation are in satisfactory agreement with experiment.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 105–108, May, 1982.     

Positron annihilation and Hall effect in electron irradiatedn-InP crystals

Positron annihilation and Hall effect inn-InP crystals as a function of electron irradiation up to 1 · 10¹⁹ cm^–2 and post-irradiated isochronal annealing up to 550 °C have been studied. It is concluded that in irradiatedn-InP samples positrons interact with negatively charged acceptor-type defect with level atE _c –0.33 eV, probablyV _In (primary defect). In post-irradiated isochronal annealed (up to 330 °C) samples ofn-InP positron trapping occurs preferably in secondary defects-vacancy clusters, which are formed in the temperature range (150–300 °C). Inn-InP crystals containing radiation induced defects the trapping rate was found to decrease with temperature in the range (300–77) K.     

Matrix reactions of alkaline earth metal atoms with ozone : Infrared spectra of the metal ozonide and metal oxide molecules

The 15°K deposition of alkaline earth metal atoms and ozone molecules at high dilution in argon yielded intense bands near 800 cm⁻¹ and in the region, 450–650 cm⁻¹. The bands near 800 cm⁻¹ showed the appropriate oxygen isotopic shifts for assignment to ν₃ of the ozonide ion; the use of scrambled isotopic ozones indicated that the metal cation is symmetrically bound to the ozonide anion which contains three oxygen atoms with two equivalent oxygens. For the case of Ca and Ba atoms and ozone, infrared absorptions appeared between 450–650 cm⁻¹ which showed appropriate oxygen isotopic shifts for vibrational assignment to several metal oxide species. In the calcium experiments, bands at 635.7 and 575.5 cm⁻¹ which showed diatomic oxygen-18 isotopic shifts were tentatively identified as (CaO)₂ species; a pair of bands at 593.0 and 592.2 cm⁻¹ were tentatively assigned to CaO₂. For the barium reactions, bands at 634.7, 571.3, and 460.0 showed appropriate oxygen-18 frequency shifts for assignment to BaO, BaO₂, and (BaO)₂, respectively. The BaO assignment was confirmed by the N₂O-nitrogen matrix reaction which yielded a nitrogen matrix counterpart for BaO at 612.4 cm⁻¹.     

Tritium isotope separation by CO2-laser irradiation at low temperatures

Tritium isotope separation by CO₂-laser induced multiphoton dissociation of CTF₃ is investigated. For the optimization of the performance of this working substance, trifluoromethane, the conditions to yield high-selectivity at high-operating pressure and low-critical fluence for complete dissociation are studied using our deconvolution procedure. The irradiation conditions are varied over the following ranges; wavenumber: 1052–1087 cm^–1, gas temperature: 25°C to –78°C, CHF₃ pressure: 5–205 Torr. The selectivities exceeding 10⁴ are observed for 85–205 Torr CHF₃ at –78°C by the irradiation at 1057 cm^–1.     

Temperature-dependent change in the nature of glass fracture under electron bombardment

We report the experimental discovery of a temperature-dependent change in the nature of glass fracture under low-energy (<10 keV) electron bombardment. This is shown to depend on the transition from the thermal-shock to the thermalfluctuation mechanism of fracture at the limiting temperature T₁ = (T_g – 150) °C. The high-temperature cleavage fracture of K8 and TF1 glasses was studied and the threshold value of the critical power initiating cleavage fracture was determined (for the glasses studied _thr = 50–70 W·sec·cm^–2).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 14–16, April, 1991.     

Laser-induced free-carrier absorption in Si single crystal

The transmitted energy density in thin single Si crystal, wafers is measured at=1.06 m as a function of the incident energy density for a Nd laser pulse of 30 ns duration. Non-linear effects begin to become important at about 0.3 J/cm². The contribution due to free-carriers is separated from the interband one by using measurements made at low energy density and at different sample temperatures in the 20°–150 °C range. The time dependence of the free-carrier concentration and of the lattice temperature is computed for different values of the Auger constant. The experimental data in the 0.2–2.5 J/cm² energy density range are fitted with an Auger constant of 10^–30 cm⁶s^–1.Work supported in part by M.P.I. and G.N.S.M.-C.N.R.     

Optical studies on free-standing polypyrrole films by the photopyroelectric method

Optical spectra of free-standing polypyrrole films were investigated by a novel PhotoPyroElectric (PPE) method. The reflection and absorption spectra in the range 2000–25000 cm^–1 of TsO^–- and ClO ₄ ^su– -doped polypyrrole films were obtained with an experimental setup comprising two pyroelectric sensors. The absorption bands due to electronic transitions to the bonding and antibonding bipolaronic levels appear at 11 000 and 21 500 cm^–1, respectively. Some relevant details in the polypyrrole spectrum in the 2000–5000 cm^–1 range were observed. The absorption band located at 3400 cm^–1 is characteristic for NH stretching vibration. The bands in the 2300–2500 cm^–1 range are ascribed to the vibration of N⁺H groups containing positively charged nitrogen. The PPE spectra also reveal changes of the electronic and vibrational absorption bands after polymer reduction and HCl treatment.     

Quadrupole interactions at57Fe in titanium metal

The electric field gradient (EFG) at⁵⁷Fe in titanium is measured using Mössbauer spectroscopy in the temperature range 80°–380°K. The value of EFG obtained at room temperature is 0.53(4)×10¹⁷ V/cm². The value of EFG obtained is compared with the conduction electron charge shift model.     

Electronic absorption spectrum of Ni2+ in lithium potassium sulphate single crystal

Single crystals of nickel-doped lithium potassium sulphate were grown by slow evaporation method at room temperature. From the nature and position of the bands observed, a successful interpretation of all the bands could be made assumingO _h symmetry for the Ni²⁺ ion in the crystal. The bands have been assigned transitions from the ground³A_2g(F) state to the excited³T_2g(F),¹E_g(D),³T_1g(F),¹T_2g(D) and³T_1g(P) states. The crystal field parameters derived areDq=910cm^–1,B=890cm^–1 andC=3560cm^–1.The authors wish to express their thanks to Prof. K. Sreerama Murthy for his constant encouragement throughout this investigation. The authors are also thankful to Prof. Mihir Chowdhury, Indian Association for the cultivation of Science, Calcutta for giving permission to take the spectra.     

Structure and electrical properties of thin films of copper selenide

Electron-diffraction and electron-microscope methods were used to investigate the structure of Cu₂Se films of close to stoichiometric composition. It is shown that in polycrystalline and single-crystal films of thickness >400Å at room temperature, the tetragonal modification is stable, which at temperatures above 400°K is transformed into the cubical modification. In thinner films d<400 Å the cubical modification of copper selenide is stable at room temperature. A sharp peak is observed at 400°K on the temperature dependence of the resistance; this is connected with the phase transition. At room temperature, copper selenide is a degenerate p-type semiconductor with carrier concentration 5 · 10²²–8 · 10²⁰ cm^–3, depending on the thickness of the film.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 90–94, August, 1973.     

Thermal redistribution of boron implants in bulk silicon and SOS type structures

The redistribution of boron profiles in bulk silicon and SOS (silicon-on-sapphire) type structures is investigated in this paper. Experimental data on thermally redistributed profiles are correlated with predictions based on a computer program whose numerical algorithm was described in an earlier paper. Three cases were considered which involved the thermal redistribution of 1) a high dose (2×10¹⁵ and 5×10¹⁴ cm^–2) 80keV boron implant in (111) bulk silicon, in an oxidizing ambient of steam at 1000°, 1100°, and 1200°C, respectively; 2) a high dose (2.3×10¹⁵ cm^–2) 25 keV boron implant in (100) silicon-on-sapphire, in a nonoxidizing ambient of nitrogen at 1000 °C; and 3) a low dose (3.2×10¹² cm^–2) 150 keV boron implant in (100) bulk silicon, in oxidizing and nonoxidizing ambients that make up the fabrication schedule of an-channel enhancement mode device. For all three cases the overall correlation of computer predictions with experimental data was excellent. Correlations with experimental data based on SUPREM predictions are also included.     

Infrared spectra of urine from cancerous bladders

The infrared spectra of organic constituents of urine from cancerous bladders of some patients were recorded. The spectra of the organic part of the samples were classified into five types according to the bulk constituents. Samples with type A spectra consisted mainly of proteins with only trace amounts of lipids. Their spectra were characterized mainly by the absorption bands of proteins at the frequencies 3330, 3075, 2960, 2850, 1650, 1530, 1450, 1400 and 1320 cm^–1, in addition to a weak band at 1720 cm^–1 due to the absorption of lipids. Samples with type B spectra were characterized by high amounts of proteins and low amounts of lipids and phosphate compounds. The presence of phosphate compounds was indicated by the absorption bands at the frequencies 1100 and 1030 cm^–1. Samples giving spectral type C were characterized by high urea contents as indicated by the presence of two strong bands at 1670 and 1630 cm^–1. Samples with the spectral type D consisted of urea and phosphate compounds whereas the last spectral type E consisted mainly of calcium oxalates, uric acids and phosphate compounds. The presence of calcium oxalates was indicated by the presence of its diagnostic bands at the frequencies 1630 and 1330 cm^–1, while the presence of uric acid was indicated by the bands at the frequencies 1360, 1130, 1020 and 880 cm^–1. On the other hand, the spectra of the organic part of urine from some normal bladders exhibited the characteristic bands of urea only.Careful examination of the spectra of the inorganic part of urine revealed that some samples consisted mainly of hydroxyapatite. The absorption bands of hydroxyapatite appeared at the frequencies 568, 603, 985, 1037 and 1128 cm^–1. The spectra of other samples showed that the bands of basic phosphates at the frequencies 568, 620, 727, 890, 1035 and 1140 cm^–1. The spectra of the inorganic part of urine from a number of normal bladders displayed the bands of basic phosphates. The relationship between urine constituents and pathological types of bladder tumor tissue was discussed.     

Temperature dependence of anisotropy in monocrystalline lithium ferrite films

A study of crystallographic and uniaxial anisotropy in monocrystalline Li-ferrite films in the temperature range 4.2–550°K is presented. The experimental results K₁(T) agree well with calculations based on the one ion model with crystalline field coefficients of a_A=–2.77 ·10^–2 cm^–1, a_B=3.34 · 10^–2 cm^–1. An experimental function K_u(T) is obtained which does not contradict the assumption that anisotropic stresses are responsible for the development of uniaxial anisotropy in Li-ferrite films.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 113–116, August, 1973.     

Low-Temperature Midinfrared Absorption in GaSe

We report the measurement of the temperature dependence of the absorption spectra of - GaSe over the temperature range 300 K to 5 K. Measurements have been made for both the e-ray (polarized parallel to the crystals c-axis) and the o-ray (polarized perpendicular to the c-axis), over the spectral range 4000 to 10 cm^–1. Nine absorption lines at 417, 440, 499, 546, 891, 945, 1015, 1093, 1270 cm^–1 were recorded at 300 K for the e- ray spectra. Some of these lines were identified using the results of a modified single layer, linear chain model of GaSe. The lines at 417, 440 and 499 cm^–1 were assigned to local impurity absorption originating from N, Mg and O, respectively. The weak lines at 945, 1015 and 1093 cm^–1 were assigned to hole transitions from the acceptor levels to the top of the valence band. Two absorption lines at 891 cm^–1 and 1270 cm^–1 were assigned to hole transitions from the quasi-local acceptor levels to the double degenerate valence sub-bands ₅ or ₆. The origin of lines recorded in the far IR absorption spectra at 20, 37 cm^–1 and 362 cm^–1 were also identified.     

Determination of the electron temperature of a degenerate semiconductor in quantizing fields under heating by an electric field

Investigations of the Shubnikov-de Haas oscillation of the transverse magnetoresistance due to the magnitude of the electric field in n-type InSb with 5 · 10¹⁵, 3 · 10¹⁶ cm^–3 concentrations at a 4.2 °K temperature are carried out herein. A method is proposed to determine the electron temperature T_e; dependences of T_e on the electric and magnetic fields in the sample are obtained for a transversely oriented magnetic field. The relaxation time of the electron energy is estimated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 96–100, February, 1972.     

FTIR and Raman spectroscopic study of Fenugreek (<Emphasis Type="Italic">Trigonella foenum graecum L.</Emphasis>) seeds

The composition of Fenugreek seeds in the form of powder, ash, and oil is investigated through FTIR and FT Raman spectra measurements. The results indicate that Fenugreek seeds (powder) are rich in proteins. Fats (lipids) and starch are present in small amounts in the seeds. The FTIR absorption bands of seed powder appeared at: 3365 cm^–1 assigned as N-H stretching vibrations (amide A of protein), 1657 cm^–1 (C=O, amide I), 1540 cm^–1 (N-H bending vibration, amide II), and 1240 cm^–1 (N-H bending, amide III). In the FT Raman spectra the band at 1661 cm^–1 is ascribed to amide I (C=O) of proteins while the band at 1080 cm^–1 indicates the starch. The fenugreek oil Fourier transform infrared absorbance ratios A(3009 cm^–1)/A(2924 cm^–1), A(3009 cm^–1)/A(2854 cm^–1), and A(3009 cm^–1)/A(1740 cm^–1) were considered for measuring the iodine values. These ratios (0.3609, 0.4916, and 0.4129) revealed that the iodine value of fenugreek oil is higher than that of other oils. On the other hand, the ash of fenugreek is very rich in phosphate compounds. The spectra showed absorption bands at frequencies 1082, 1000, 618, and 566 cm^–1, and the FT Raman spectrum showed a strong absorbance band at 793 cm^–1, which is due to phosphate compounds. It could be concluded that the inorganic part of fenugreek consists mainly of phosphate compounds. The Fenugreek seed contains proteins, fat, fiber, and ash, which is in complete harmony with AACC, 1980.__________Published in Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 1, pp. 106–110, January–February, 2005.     

Anomalous photoluminescence and raman scattering behavior in heavily Mg+ ion-implanted InP

Mg⁺ ions were implanted into highly pure InP grown by the liquid encapsulated Czochralski (LEC) method in which the Mg concentration [Mg] was varied between 1×10¹⁵ cm^–3 and 3×10²⁰ cm^–3. Two annealing methods were used: furnace annealing (FA) up to 740° C and flash lamp annealing (rapid thermal annealing, RTA) up to 900° C. For characterization, photoluminescence (PL) spectra were measured between 2K and room temperature together with Raman scattering measurements at room temperature. An emission designated by g, which was attributed to a novel energy state of an isolated acceptor, was found to be produced for a rather low value of [Mg]. In addition, a broad emission denoted by [g–g], which was ascribed to acceptor-acceptor pairs, was observed below bound exciton emissions for moderate values of [Mg]. These features were quite similar to those previously observed in acceptor-doped GaAs when the background concentration of donors is extremely low. Two additional novel emissions located far below the band-to-acceptor emission were also obtained, and each showed a remarkable energy shift towards lower energy with increasing [Mg]. The binding energies of these emissions were estimated from the temperature dependence of PL spectra and the results suggest that they are complex-type radiative recombination centers, presumably donor-acceptor-type centers. A strong broad emission centered near the band-to-acceptor emission was observed for [Mg]=3×10²⁰ cm^–3. This observation indicates a formation of a new material between In, P and Mg, which was also attested by the appearance of a new TO-like Raman signal for [Mg] greater than 1×10¹⁹ cm^–3. A substantial difference of PL and Raman spectra was revealed for the two annealing methods, suggesting that the annealing behaviour of ion-implanted InP should be investigated more extensively in order to establish reliable annealing procedures.Dedicated to H.-J. Queisser on the occasion of his 60th birthday     

Formation of thermally stable low-resistance Ti/W/Au ohmic contacts on n-type GaN

A Ti(12 nm)/W(20 nm)/Au(50 nm) metallization scheme has been investigated for obtaining thermally stable low-resistance ohmic contacts to n-type GaN (4.0×10¹⁸ cm^-3). It is shown that the current–voltage (I–V) characteristics of the samples are abnormally dependent on the annealing temperature. For example, the samples that were annealed at temperatures below 750 °C for 1 min in a N₂ ambient show rectifying behavior. However, annealing the samples at temperatures in excess of 850 °C results in linear I–V characteristics. The contact produces a specific contact resistance as low as 8.4×10^-6 Ω cm² when annealed at 900 °C. It is further shown that the contacts are fairly thermally stable even after annealing at 900 °C; annealing the samples at 900 °C for 30 min causes insignificant degradation of the electrical and structural properties. Based on glancing angle X-ray diffraction and Auger electron microscopy results, the abnormal temperature dependence of the ohmic behavior is described and discussed. PACS 72.80.Ey; 73.40.Cg; 73.20.At; 79.60Bm; 73.40.Gk