Changes in the optical and electrophysical properties of langmuir films of liquid crystals upon a ferroelectric phase transition

The adsorption isotherms of water molecules, spectra of diffuse reflection and of reflected-light polarization, and electrophysical properties of hyperfine films fabricated on the basis of liquid crystals have been studied. A structural phase transition was detected at a temperature of about 70°C; near the transition, features of light polarization, of the reflection coefficient’s behavior, and of the temperature dependence of the sample capacitance have been found. Hypotheses regarding the nature of the phase transition are proposed.     

Dielectric properties of thin PbTiO<Subscript>3</Subscript> films

The electrophysical properties and phase composition of thin lead titanate films prepared on various substrates by layer-by-layer magnetron sputtering of metals followed by annealing have been studied. The main parameters of the metal-ferroelectric film-metal multilayer structures, namely, the spontaneous polarization, coercive field, and permittivity, were studied for various substrate types and electrode materials. The conditions favorable for the formation of PbTiO₃ films that are similar in stoichiometry and phase composition were established.     

The influence of ion irradiation on the structure and properties of amorphous carbon films

Presented in this work are the results of investigation of the structure and electrophysical properties of amorphous carbon films. The films were produced by sputtering of graphite by ion beam and usin ion irradiation (E=0–200 eV) during condensation process. The structure of i-C films has been studied by means of transmission electron microscope. The electron diffraction data have been interpretated by employing the calculated interference function of carbon clusters. The structure of V-band was obtained from AES by deconvolution method. Experimental data shows that under ion irradiation the transformation of short range order and electron bonds is an oscillating function of ion energy E. This paper presents a theoretical calculation of tunneling neutralization cross-section of Ar⁺ ions on carbon surface. The process also has an oscillating dependence on ion energy. A significant importance of inelastic processes in carbon phase transformation has been revealed.     

Structure and properties of ZnSe nanocomposite thin films

The structure and electrophysical and optical properties of semiconductor ZnSe nanocomposite thin films are studied. These films are obtained by discrete thermal evaporation in an ultrahigh vacuum. ZnSe films are synthesized in various structural states in the condensation temperature range 2–200°C. The optical spectra of these films are studied in the visible region.     

Annealing atmosphere effect on the processes of recrystallization of polycrystalline films of cadmium selenide

Using the example of polycrystalline films CdSe doped with I group elements by means of ion implantation, the structure rearrangement processes, including recrystallization, under annealing in various environments are discussed in detail. The interrelation of recrystallization and activation of an implanted impurity is found; it is shown that structural transformations under film recrystallization have a determining effect on activation of the implanted impurity and, as a consequence, on electrophysical and photoelectric properties of recrystallized films.     

The Effect of Synthesis Temperature on the Microstructure and Electrophysical Properties of BST 80/20 Films

Physics of the Solid State - In this paper, we show the effect of synthesis temperature on the microstructure and electrophysical properties of ferroelectric Ba0.8Sr0.2TiO3 films during the...     

The Influence of the Percolation Transition on the Electric Conductive and Optical Properties of Ultrathin Metallic Films

Physics of the Solid State - The results of the study of the peculiarities of changes in the electrophysical, optical, and plasmonic properties of ultrathin metallic films during the percolation...     

Nanostructured heterophase thin films of lead zirconate titanate

The results of a comprehensive study of electrophysical and photoelectric properties of capacitor structures are analyzed within the proposed model of Pb(ZrTi)O₃ (PZT) films with an excess lead content, which is based on the presence of heterophase intergrain boundaries. It is shown that aging of thin-film capacitor structures is accompanied by a significant increase in the oxygen content in submicron PZT films, as well as by the modification of elemental and phase compositions of the interfaces. It is confirmed experimentally that a decrease in the switching charge in the aged PZT films is due to the oxygen sorption at heterophase crystallite boundaries containing lead oxide and to pinning of the polarization in regions adjacent to the charged boundaries. It is demonstrated that the current-voltage characteristics of the capacitor structures are described in terms of the mechanisms of space-charge-limited currents.     

Temperature dependence of the conductance and capacitance of langmuir films of liquid crystals

Langmuir films of various thicknesses, fabricated based on liquid crystals, have been studied. Previously, a structural phase transition at a temperature of ～75°C was detected for these films. To determine the nature of this transition, the temperature dependences of the capacitance and conductance of the metal-Langmuir film-metal structures have been measured. The results obtained suggest that the ferroelectric phase in the studied samples exists beginning with one monolayer. The length of the temperature interval in which the phase transition is observed indicates a film structure imperfection.     

Changes of thermo-morphologic and thermotropic properties of liquid crystals at direct and reverse nematic mesophase ↔ isotropic liquid phase transitions: surface-induced effect

In this work, the effect of thin films on the thermo-morphologic and thermotropic properties of the phase transitions between the nematic mesophase and isotropic liquid has been investigated. Investigations have been carried out for both the heating and cooling processes. The temperature and linear widths of the biphasic regions of the direct and reverse phase transitions in nematic liquid crystals versus thickness of the thin films have been calculated with a high accuracy. The shift of the nematic mesophase–isotropic liquid and the isotropic liquid–nematic mesophase phase transition temperatures to higher temperatures and the enlargement of the temperature and linear widths of the biphasic regions as the effect of surfaces have been found.     

Ferropiezoelectric properties and microstructure of PbFe1/2Nb1/2O3 ceramics

Ceramic samples of lead ferroniobate (PFN) having a rhombohedral symmetry at room temperature are obtained. Their ferroelectric and magnetic properties in the vicinity of the antiferromagnetic and ferroelectric phase transition temperatures are investigated. The electrophysical parameters of the polarized ceramic are presented. By means of electron-probe microanalysis, the number of inclusions of Fe-containing impurity phases (??0.2 vol %) is revealed to be several times higher than that in grains of the PFN ceramics. It is suggested that the above could be caused by the magnetic properties of PFN at room temperature.     

纳米二氧化钒薄膜的电学与光学相变特性

采用双离子束溅射氧化钒薄膜附加热处理的方式制备了纳米二氧化钒薄膜。在热驱动方式下,分别利用四探针测试技术和傅里叶变换红外光谱技术对纳米二氧化钒薄膜的电学与光学半导体-金属相变特性进行了测试与分析。实验结果表明,电学相变特性与光学相变特性之间存在明显的偏差,电学相变温度为63 ℃,高于光学相变温度,60 ℃;电学相变持续的温度宽度较光学相变持续温度宽度宽;在红外光波段,随着波长的增加,纳米二氧化钒薄膜的光学相变温度逐渐增大,由半导体相向金属相转变的初始温度逐渐升高,相变持续的温度宽度变窄。在红外光波段,纳米二氧化钒薄膜的光学相变特性可以通过光波波长进行调控,电学相变特性更适合表征纳米VO₂薄膜的半导体-金属相变特性。     

Non-debye dielectric response in monolithic layers of silver stearate

This paper reports on the results of investigations of the electrophysical properties of silver stearate by the methods of dielectric spectroscopy and differential scanning calorimetry (DSC). The mechanisms of charge transfer and dielectric relaxation in silver stearate have been established. It has been found that there is a critical temperature T = 338 K, which is probably related to the low-temperature phase transition in the system under investigation.     

Structural and electrophysical characteristics of YBCO films on sapphire

We present experimental results for the structural and electrophysical characteristics of YBCO films deposited on sapphire substrates without an interface layer. The films were deposited by laser sputtering of a target. We establish certain relationships between the structural and electrophysical characteristics of the films. We show the films’ electrophysical parameters are determined by the number of "defective" blocks whose [010] axes are at random angles relative to the [100] axis of the substrate. V. D. Kuznetsov Siberian Physicotechnical Institute, Tomsk University. Translated from Izvestiya Vysshikh Uchebnykh Zaved, Fizika, No. 5, pp. 75–78, May, 1998.     

Phase transitions in PbSc0.5Ta0.5O3

Ordered and partially ordered PbSc_0.5Ta_0.5O₃ ferroelectric single crystals are studied by diffraction, electrophysical, and optical methods. X-ray diffraction and electrophysical methods indicate the presence of a phase transition in the low-temperature range (at T = ?40°C).     

Hydrogen and helium films as model systems of wetting

Optical experiments on the wetting properties of liquid ⁴He and molecular hydrogen are reviewed. Hydrogen films on noble metal surfaces serve as model systems for studying triple point wetting, a continuous transition between wetting and non-wetting. By means of optically excited surface plasmons, the adsorbed film thickness for temperatures around, and far below, the bulk melting temperature is measured, and the physical mechanisms responsible for the transition are elucidated. Possible applications for other experiments in pure and applied research are discussed. Thin films and droplets of liquid helium are studied on cesium surfaces, on which there is a first order wetting transition. Our studies concentrate on dynamical observations via surface plasmon microscopy, which provide insight into the morphology of liquid helium droplets spreading at different temperatures. Features corresponding to pinning forces, the prewetting line, and the Kosterlitz-Thouless transition are clearly observed.     

Electrophysical properties of anode oxide films on an indium antimonide surface

Anode oxide films are widely used for the passivation of the surface of semiconductors of group A^IIIB^V (GaAs [1–5], InSb [6–8], InAs [9], etc.) and as a subgate dielectric in MOS devices on a base of these materials. As well as a study of the properties of the boundary of separation of an anode oxide-semiconductor, the investigation of the electrophysical properties of such anode oxide films is an independent and extremely important problem. This is due to the fact that such characteristics of MOS devices as the charge stability, hysteresis phenomena, leakage currents through the gate, etc., are largely determined by the volume properties of the dielectric layer (by the spectrum of localized electron states in the volume, the mechanism of charge transfer through the dielectric film, etc.). At the same time, much less attention has been paid to the study of the properties of anode oxide films than to the investigations of the boundary of separation of a dielectric and a semiconductor. In this paper we investigate the electrophysical properties of anode oxide films of indium antimonide obtained by anode oxidation of a semiconductor substrate in a 0.1 N aqueous solution of KOH. We measured the dependence of the capacitance of the anode oxide on frequency (f), on temperature (T), and on the bias voltage (V), as well as the DC current-voltage characteristics.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 79–83, April, 1981.     

The effect of ultraviolet irradiation on the properties of Zr/Si contacts

The effect of ultraviolet (UV) irradiation on the properties of Zr/Si contacts subjected to heat treatment is investigated. It is established that, due to variations in the phase composition of the contact, its electrophysical parameters are modified. The application of the combined treatment allows one to form Zr/Si contacts with specified properties.     

Electrophysical properties of MIS structures with nanodimensional β-cyclodextrin Langmuir-Blodgett films

Mixed cyclodextrin-phenanthrene monolayers at the water-air interface are studied. The formation conditions for Langmuir-Blodgett films on single-crystalline substrates are found. Aluminum/Langmuir-Blodgett film/single-crystal n-Si structures are obtained, and their properties are investigated by taking current-voltage and lux-ampere characteristics. The deposition conditions of the Langmuir-Blodgett film and its thickness are shown to influence the electrophysical and photoelectric properties of the heterostructures.     

Changes in optical properties of TDO BAM BCC Langmuir films during a phase transition

The isotherms of water molecule adsorption and the spectra of absorption, diffusion reflection, and polarization of reflected light for hyperfine Langmuir films that were fabricated based on liquid crystals are investigated. Singularities in the reflection spectra at the temperature of the structural phase transition (∼70°C) are revealed. Some reasonable assumptions on the nature of the phase transition are made.