A. N. Moiseev

Low-loss, high-purity (TeO2)0.75(WO3)0.25 glass

By melting a mixture of high-purity oxides in a platinum crucible under flowing purified oxygen, we have prepared (TeO2)0.75(WO3)0.25 glass with a total content of 3d transition metals (Fe, Ni, Co, Cu, Mn, Cr, and V) within 0.4 ppm by weight, a concentration of scattering centers larger than 300 nm in size below 102 cm−3, and an absorption coefficient for OH groups (λ ∼ 3 μm) of 0.008 cm−1. The absorption loss in the glass has been determined to be 115 dB/km at λ = 1.06 μm, 86 dB/km at λ = 1.56 μm, and 100 dB/km at λ = 1.97 μm. From reported specific absorptions of impurities in fluorozirconate glasses and the impurity composition of the glass studied here, the absorption loss at λ ∼ 2 μm has been estimated at ≤100 dB/km. The glass has been drawn into a glass-polymer fiber, and the optical loss spectrum of the fiber has been measured.

Preparation of high-purity TeO2-ZnO glass batches

Tellurium oxide-zinc oxide glass batches have been prepared through chemical vapor deposition from tellurium and zinc alkyl compounds in an oxyhydrogen flame onto the lateral surface of rotating cylindrical substrates. The composition of the deposits has been shown to be determined by the relative amounts of the metalorganic precursors in the gas phase. Varying the deposition conditions, we obtained both amorphous and crystalline deposits, with concentrations of metallic impurities below 1 ppmw. Melting the deposits, we prepared high-purity (TeO2)1 − x(ZnO)x (0.15 ≤ x ≤ 0.35) glasses.

Coprecipitation of tellurium and molybdenum oxides from aqueous solutions

We report the preparation of mixtures of tellurium and molybdenum oxides of controlled composition through the precipitation of tellurous and molybdic acids from hydrochloric acid solutions of tellurium(IV) and molybdenum(VI) compounds. We have established general trends in the distribution of macrocomponents between the precipitate and solution and shown the feasibility of quantitative tellurium(IV) and molybdenum(VI) precipitation in a weakly acidic medium. After drying and calcination, the precipitates were tested as TeO2-MoO3 glass batches.

Fine Purification of Monoisotopic Silanes 28SiH4 , 29SiH4 , and 30SiH4 via Distillation

High-purity isotopically enriched (99.98% 28Si, 99.57% 29Si, and 99.83% 30Si) silane samples are prepared for the first time. The total hydrocarbon content of the samples is no higher than 0.1–0.3 ppm. The concentration of electroactive impurities in the silicon prepared from the purified monoisotopic silane is below 1015 cm–3.

Thermodynamic properties of (TeO2)0.95 − n − z (ZnO) z (Na2O) n (Bi2O3)0.05 glasses

AbstractThe heat capacity (Cp0) of the tellurite glasses

MOCVD of p-CdxHg1 – xTe/GaAs Heteroepitaxial Structures

\begin{gathered} (TeO_2 )_{0.70} (ZnO)_{0.15} (Na_2 O)_{0.10} (Bi_2 O_3 )_{0.05} (I), \hfill \\ (TeO_2 )_{0.75} (ZnO)_{0.10} (Na_2 O)_{0.10} (Bi_2 O_3 )_{0.05} (II),and \hfill \\ (TeO_2 )_{0.75} (ZnO)_{0.15} (Na_2 O)_{0.05} (Bi_2 O_3 )_{0.05} (III) \hfill \\ \end{gathered}

Impurity composition of molybdate-tellurite glasses prepared from mixtures precipitated from hydrochloric acid solutions of tellurium and molybdenum compounds by ammonia

has been measured in the temperature range 255–750 K using a differential scanning calorimeter (glasses I–III) and in the range 208–325 K using an adiabatic calorimeter (glass II). We have determined the temperature ranges of the glass transition, evaluated the thermodynamic characteristics of the glass transition and glassy state, and estimated the crystallization onset temperatures. Using the experimental data and a statistical model approach, we have calculated the standard thermodynamic functions for glassy and “supercooled liquid” states in the temperature range 0–740 K: heat capacity Cp0(T), enthalpy H0(T) − H0(0), entropy S0(T) − S0(0), and Gibbs function G0(T) − G0(0).

Electrophysical Properties of p -Type Undoped and Arsenic-Doped Hg 1 – x Cd x Te Epitaxial Layers with x ≈ 0.4 Grown by the MOCVD Method

Metalorganic chemical vapor deposition from Cd and Te alkyl compounds and Hg vapor is used to grow p-type CdxHg1 – xTe epitaxial layers on semi-insulating GaAs(111)Bsubstrates by the interdiffused multilayer process (alternating CdTe and HgTe layers) at a substrate temperature of 350°C, followed by postgrowth annealing. Layers are obtained with x = 0.2–0.4, 77-K carrier concentrations in the range (1–5) × 1016 cm–3, and 77-K carrier mobilities from 200 to 400 cm2 /(V s). The rocking curves of the epilayers have a full width at half maximum in the range 2–4 min of arc.

Growth of arsenic-doped cadmium telluride epilayers by metalorganic chemical vapor deposition

Molybdate-tellurite glasses have been prepared from precipitates obtained by adding aqueous ammonia to hydrochloric acid solutions of tellurium(IV) and molybdenum(VI) compounds. The impurity compositions of the precipitates and glasses have been determined by atomic emission spectroscopy. The results indicate that contamination with metal impurities occurs mainly in the precipitate washing step. Prolonged holding of a glass-forming melt in a porcelain crucible leads to contamination of the glass with aluminum, magnesium, and calcium.

Effect of eddy formation on gas mixture homogeneity near a substrate in a vertical reactor for CdHgTe deposition

The temperature dependences of the charge-carrier concentration and lifetime of minority carriers in undoped and arsenic-doped p-type Hg1 – xCdxTe epitaxial layers with x ≈ 0.4 grown by the MOCVD-IMP (metalorganic chemical vapor deposition–interdiffusion multilayer process) method are studied. It is shown that the temperature dependences of the charge-carrier concentration can be described by a model assuming the presence of one acceptor and one donor level. The ionization energies of acceptors in the undoped and arsenic-doped materials are 14 and 3.6 meV, respectively. It is established that the dominant recombination mechanism in the undoped layers is Shockley–Read–Hall recombination, and after low-temperature equilibrium annealing in mercury vapors (230°C, 24 h), the dominant mechanism is radiative recombination. The fundamental limitation of the lifetime in the arsenic-doped material is caused by the Auger-7 process. Activation annealing (360°C, 2 h) of the doped layers makes it possible to attain the 100% activation of arsenic.