Growth of In-Doped PbTe Films on Si Substrates

Data on the evaporation behavior of Pb_{1 – x} In _x (0.10 x 0.70) melts were used to devise a procedure for the growth of vapor-phase In doped PbTe thin films on Si substrates. This approach offers the possibility of growing single-phase, homogeneous Pb_{1 – y} In _y Te films of controlled composition by adjusting the composition and temperature of Pb_{1 – x} In _x (0.10 x 0.50) melts. X-ray diffraction characterization demonstrates that the films grown on Si with no oxide layer consist of slightly misoriented crystallites, with their (100) axes normal to the film surface, whereas the films grown on substrates covered with a SiO₂ layer are polycrystalline, with a strong (100) texture.     

Ga Doping of Thin PbTe Films on Si Substrates during Growth

In depositing thin PbTe films onto Si substrates by a modified hot-wall method, Pb_{1 – x} Ga _x melts were used as Ga vapor sources in combination with separate Pb and Te sources. Data on the vaporization behavior of Pb_{1 – x} Ga _x melts were used to devise a new technique for reproducible growth of PbTe/Si and PbTe/SiO₂/Si structures. The lattice parameter of the PbTe films was found to vary nonmonotonically with Ga content, which was interpreted as evidence that the dopant can be incorporated by different mechanisms. Conductivity and Hall effect measurements between 77 and 300 K reveal a nonmonotonic variation of carrier concentration with doping level and suggest that Ga is an amphoteric impurity in narrow-gap IV–VI semiconductors.     

Structural Perfection of PbTe Films Doped with Indium during Growth on Si Substrates

Pb_{1 - y} In _y Te films doped during growth are produced by a modified hot-wall method. According to x-ray diffraction and electron microscopy data, the films withy _tot < 0.012 are single-phase. The films with y _tot > 0.014 consist of two (PbTe + InTe) or three (PbTe + InTe + In₂Te₃) phases. The 583-K indium solubility in PbTe is determined in the ternary system Pb-In-Te. The results indicate that two pseudobinary joins, PbTe-InTe and PbTe-In₂Te₃, must be examined in assessing the In solubility in PbTe.     

Ionic conductivity of BaF<Subscript>2</Subscript> + ZnF<Subscript>2</Subscript> + CdF<Subscript>2</Subscript> + YbF<Subscript>3</Subscript> optical fluoride ceramic

The electrical conductivity of an optical fluoride ceramic in the quaternary system BaF₂ + ZnF₂ + CdF₂ + YbF₃ has been determined in the temperature range 338–722 K using impedance spectroscopy (5 to 5 × 10⁵ Hz). The 500-K ionic conductivity of the ceramic is σ = 3.3 × 10^–4 S/cm, which corresponds to the electrical characteristics of single crystals of the best conducting nonstoichiometric M_1–x R _x F_{2 + x} (M = Sr, Ba; R = La–Nd; x = 0.3–0.5) fluorite phases. We have observed nonmonotonic variation (breaks) in temperature-dependent σ, which is due to competing fluoride ion transport processes in different parts of the ceramic sample. The highly conductive state of the BaF₂ + ZnF₂ + CdF₂ + YbF₃ fluoride ceramic seems to be due to the formation of structural regions corresponding to a Ba_1–x Yb _x F_{2 + x} solid solution.     

Absorption and luminescence spectra of CeF<Subscript>3</Subscript>-doped BaF<Subscript>2</Subscript> single crystals and nanoceramics

We have studied the radiation resistance of BaF₂:Ce³⁺ scintillator single crystals and ceramics at gamma doses from 10⁶ to 10⁸ rad. It has been shown that the ceramics produced using the self-fluorinating precursor BaF₂ ? HF is more radiation-resistant.     

Thin-film PbSnTe:In/BaF<Subscript>2</Subscript>/CaF<Subscript>2</Subscript>/Si structures for monolithic matrix photodetectors operating in the far infrared range

We report for the first time on the creation of 288 × 2 matrix photodetectors with an element size of 25 × 25 μm based on PbSnTe:In/BaF₂/CaF₂/Si structures and present their threshold characteristics. The detection ability of about 90% elements ranges from 7.2 × 10¹² to 8.7 × 10¹² cm Hz^0.5/W at T = 21.2 K. The proposed technology opens ways to the creation of monolithic matrix photodetectors operating in the far-IR range.     

Epitaxial Growth of CeO<Subscript>2</Subscript>/YSZ/CeO<Subscript>2</Subscript> Buffer Layers on Textured Ni Substrates for YBCO Conductors

CeO₂/YSZ/CeO₂ buffer layers were deposited on textured Ni substrates byin situ pulsed laser deposition. The out-of-plane texture and in-plane texture of the buffer layers were characterized by X-ray diffraction ω-scans and ϕ-scans. Using this CeO₂/YSZ/CeO₂ architecture as the buffer layers, high quality YBCO films with a zero-resistanceT _c about 90 K and a self-field critical current densitiesJ _c above 10⁶ A/cm² at 77 K can be obtained on Ni substrates.     

Phonons in mixed superionic fluorites (BaF<Subscript>2</Subscript>)<Subscript>1-x</Subscript>(LaF<Subscript>3</Subscript>)<Subscript>x</Subscript>

In recent years, the fluorite-structured solid solutions with the general formula, (MF₂)_1-x(RF₃)_x (M = Ca, Sr, Ba, Pb and R is a rare-earth element or Y), have been the subject of numerous experimental studies focussed on their superionic properties. The overall cubic crystal symmetry (space group Fm3m) is conserved up to x ≶ x_max, where x_max ⊁ 0.4-0.5 depending on M and R. The zone centre phonons and phonon dispersion along three symmetry directions of the mixed superionic compound (BaF₂)_1-x(LaF₃)_x have been investigated by applying de Launey angular force model for x ≶ x_max. The calculated results are compared and explained with available experimental results.     

Epitaxial YBa<Subscript>2</Subscript>Fe<Subscript>3</Subscript>O<Subscript>8</Subscript> Films Prepared by Chemical Solution Deposition Method

YBa₂Fe₃O₈(YBFO) epitaxial films are prepared on (100) SiTrO₃ single crystal substrate by polymer-assisted non-fluorine chemical solution deposition (CSD) method. The influence of firing temperature on texture degree, microstructure, and physical properties of YBFO films is systematically investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and SQUID magnetometer. YBFO film fired at 1070 °C exhibits best epitaxial quality with FWHM value of (103) phi-scan and (005) omega-scan is 0.19° and 0.45°, respectively, and highly dense and smooth morphology. A weak ferromagnetism transition was observed at 68 K in the YBFO film.     

Transport Properties of Ga-Doped PbTe Thin Films on Si Substrates

Thin PbTe films on Si substrates were doped with Ga via annealing in the vapor produced by heating a Ga(l) + GaTe(s) mixture (GaTe(s) + L ₁+ Vequilibrium). Electrical measurements showed that the vapor-phase doping reduced the hole concentration in the films by more than two orders of magnitude. IR irradiation was found to reduce the resistivity of the PbTe films by a factor of 40–100. The films annealed in the vapor over GaTe(s) + L ₁for the longest time exhibited an anomalous temperature variation of resistance, which was interpreted as due to the limited Ga solubility in PbTe.     

Growth and properties of LiCu<Subscript>2</Subscript>O<Subscript>2</Subscript>-NaCu<Subscript>2</Subscript>O<Subscript>2</Subscript> crystals

Platelike Li_{1 ? x} Na _x Cu₂O₂ single crystals up to 2 × 10 × 10 mm in dimensions have been grown by slowly cooling (1 ? x)Li₂CO₃·xNa₂O₂·4CuO melts in alundum crucibles in air. Li_{1 ? x} Na _x Cu₂O₂ solid solutions in the LiCu₂O₂-NaCu₂O₂ system have been shown to exist in the composition range 0.78 < x < 1. The temperature stability ranges of NaCu₂O₂ and LiCu₂O₂ are 780–930 and 890–1050°C, respectively. The Mössbauer spectra and electrical conductivity of the crystals have been measured.     

Galvanomagnetic Properties of Bi<Subscript>95</Subscript>Sb<Subscript>5</Subscript> Thin Films on Substrates with Different Thermal Expansions

Results of an investigation of galvanomagnetic properties of Bi₉₅Sb₅ block thin films on substrates with different coefficients of thermal expansion covered with polyimide are presented. The difference between thermal expansions of the film material and the substrate was found to have a strong effect on the films’ galvanomagnetic properties. Analysis of the properties of the films using the two-band model showed that the concentration and mobility of the charge carriers in the Bi₉₅Sb₅ films are related to the coefficient of thermal expansion of the substrate material.     

Effect of Sn Doping on the Crystallization Kinetics of Amorphous TlInS<Subscript>2</Subscript> Films

The crystallization of amorphous Sn-doped TlInS₂ films into three polymorphs has been studied by kinematic electron diffraction. The results demonstrate that the crystallization of 30-nm-thick amorphous films produced by thermal evaporation in high vacuum can be described by the Avrami–Kolmogorov equation: V_τ = V₀[1–exp(–kτ^m)]. Kinematic electron diffraction patterns of the TlIn_1–хSn_xS₂ films have been used to assess the effect of doping with Sn on the growth dimensionality and the activation energy for the crystallization of the amorphous films and the unit-cell parameters of the resultant crystalline materials. Doping extends the temperature range and effective activation energy for the crystallization of the amorphous films.     

Preparation of La<Subscript>2</Subscript>NiMnO<Subscript>6</Subscript> thin films on Pt/TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript>/Si substrates by pulsed laser deposition

Double perovskite La₂NiMnO₆ thin films were prepared on Pt/TiO₂/SiO₂/Si substrates by the pulsed laser deposition process, and the crystal structure and microstructures were investigated. The temperature and the oxygen pressure played the primary roles dominating the crystallization behavior and the morphology of La₂NiMnO₆ thin films. The well crystallized La₂NiMnO₆ thin films could be obtained at 873 and 923 K under all oxygen pressures investigated here, and the fine morphology was obtained under the oxygen pressures equal to or higher than 50 and 100 Pa, respectively, while phase constitution was significantly affected by the oxygen pressure for La₂NiMnO₆ thin films prepared at 1,023 K where the higher oxygen pressure led to the appearance of some secondary phase.     

Microstructure and dielectric properties of BaTiO<Subscript>3</Subscript>-CeO<Subscript>2</Subscript>-SnO<Subscript>2</Subscript> ceramics

We have studied the effect of codoping with CeO₂ and SnO₂ (2 to 3.5 wt %) on the microstructure and dielectric properties of BaTiO₃. Doping with CeO₂ and SnO₂ inhibits grain growth in BaTiO₃ and enables the fabrication of ceramic materials with a grain size below 1 μm. The temperature coefficient of permittivity of the ceramics increases with CeO₂ + SnO₂ content, firing temperature, and firing time.     

Microstructure and high-temperature strength of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/Er<Subscript>3</Subscript>Al<Subscript>5</Subscript>O<Subscript>12</Subscript>/ZrO<Subscript>2</Subscript> ternary melt growth composite

A new Al₂O₃/Er₃Al₅O₁₂(EAG)/ZrO₂ ternary MGC (Melt Growth Composite) with a novel microstructure has been fabricated by unidirectional solidification. This ternary MGC has a microstructure consisting of continuous networks of single-crystal Al₂O₃, single-crystal EAG and fine cubic-ZrO₂ phases without grain boundaries. The ternary MGC has also characteristic dimensions of the microstructure of around 2–4 m for EAG phases, around 2–4 m for Al₂O₃ phases reinforced with around 0.4–0.8 m cubic-ZrO₂ phases. No amorphous phases are formed at interfaces between phases in the ternary MGC. The ternary MGCs flexural strength at 1873 K is approximately 700 MPa, more than twice the 330 MPa of the Al₂O₃/EAG binary MGC. The fracture manner of the Al₂O₃/EAG/ZrO₂ ternary MGC at 1873 K shows the same intergranular fracture as the Al₂O₃/EAG binary MGC, but is significantly different from the transgranular fracture of the sintered ceramic.     

Cu<Subscript>2</Subscript>O and CuO Films Produced by Chemical and Anodic Oxidation on the Surface of Copper Foil

The processes underlying the chemical and anodic oxidation of the surface of copper foil have been studied by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. It has been shown that, in the case of anodic oxidation, at a given process duration (τ) the composition and density of initially forming Cu(OH)₂ films depend not only on the current density (j_a) but also on whether or not the electrolyte is stirred. A Cu₂O film with an optimal, coral-like structure has been produced by the anodic oxidation of copper foil for τ = 10 min at j_a = 5 mA/cm² without stirring, followed by the thermal reduction of the Cu(OH)₂ in a nitrogen atmosphere for 1 h at 500°C. In the case of the chemical oxidation of the copper foil surface, similar Cu₂O films with a coral-like structure can also be produced by the thermal reduction of initially forming Cu(OH)₂ at 500°C for 1 h.     

Studies on Micro-Structure of Nano-ZrO<Subscript>2</Subscript> Films

In this paper, the micro-structure and laser damage threshold of nano-ZrO₂ thin films were investigated. High-purity nano-ZrO₂ particles as the coating materials of samples were prepared by electron beam evaporation. The crystallitic size and surfaces’ roughness of the samples were analyzed. The laser damage threshold test used a 1064 nm, 10 ns, 3 Hz Nd:YAG laser. The experimental results showed that oxygen partial pressure has an important influence on the micro-structure of nano-ZrO₂ films, and also we found that the laser damage threshold was dependent on the micro-structure.     

The Development of Microstructure and Ferroelectric Properties of Bi<Subscript>4</Subscript>Ti<Subscript>3.96</Subscript>Nb<Subscript>0.04</Subscript>O<Subscript>12</Subscript> Thin Films

Bi₄Ti_3.96Nb_0.04O₁₂ thin films were successfully deposited on Pt(111)/Ti/SiO₂/Si(100) substrates by a sol–gel method and rapid thermal annealing. The effects of Nb-substitution and annealing temperature (500–800°C) on the microstructure and ferroelectric properties of bismuth titanate thin films were investigated. X-ray diffraction analysis reveals that the intensities of (117) peaks are relatively broad and weak at annealing temperatures smaller than 700°C. With the increase of annealing temperature from 500°C to 800°C, the grain size of Bi₄Ti_3.96Nb_0.04O₁₂ thin films increases. The Bi₄Ti_3.96Nb_0.04O₁₂ thin films annealed at 700°C exhibit the highest remanent polarization (2P _r), 36 μC/cm² and lowest coercive field (2E _c), 110 kV/cm. The improved ferroelectric properties can be attributed to the substitution of Nb⁵⁺ to Ti⁴⁺ in Bi₄Ti₃O₁₂ assisting the elimination of defects such as oxygen vacancy and vacancy complexes.     

Growth of Y<Subscript>3</Subscript>Fe<Subscript>5</Subscript>O<Subscript>12</Subscript> films on Si with AlO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> and SiO<Subscript>2</Subscript> buffer layers by ion beam sputtering

Amorphous yttrium iron garnet films ranging in thickness from 100 to 600 nm have been produced on single-crystal silicon substrates by sputtering a polycrystalline target with the composition Y₃Fe₅O₁₂ (yttrium iron garnet) by a mixture of argon and oxygen ions. Before film growth, AlO _x or SiO₂ buffer layers up to 0.8 μm in thickness were grown on the Si surface. The heterostructures were crystallized by annealing in air at a temperature of 950°C for 30 min. The properties of the films were studied by magneto-optical techniques, using Kerr effect and ferromagnetic resonance measurements. The Gilbert damping parameter reached 2.8 × 10^–3 and the effective planar magnetic anisotropy field was independent of the nature of the buffer layer. This suggests that the thin-film heterostructures obtained in this study are potentially attractive for use in spin-wave semiconductor devices.