Method of envelopes for studying a two-film system on a reflecting substrate

For determining the optical constants and the thickness of thin films (including strongly absorbing films) by the spectrophotometric method, we propose to deposit them on intermediate films formed on strongly reflecting substrates. Due to this, an interference pattern depending on the optical constants and the thickness of the film under study will be observed in the reflectance spectrum. The method of envelopes of the extrema in the reflectance spectrum that is based on the iterative approach is developed for studying two-film systems.     

Growth and sacrificial oxidation of transition metal nanolayers

Growth and oxidation of Au, Pt, Pd, Rh, Cu, Ru, Ni and Co layers of 0.3-4.3 nm thickness on Mo have been investigated with ARPES and AFM. Co and Ni layers oxidize while the Mo remains metallic. For nobler metals, the on top O and oxidation state of subsurface Mo increase, suggesting sacrificial e⁻ donation by Mo. Au and Cu, in spite of their significantly lower surface free energy, grow in islands on Mo and actually promote Mo oxidation. Applications of the sacrificial oxidation in nanometer thin layers exist in a range of nanoscopic devices, such as nano-electronics and protection of e.g. multilayer X-ray optics for astronomy, medicine and lithography.     

Ellipsometric technique for determining in situ the absorption coefficient of semiconducting nanolayers

An algorithm that makes it possible to solve the inverse problem of ellipsometry aimed at determining the absorption coefficient on the basis of a single-zone ellipsometric experiment during the growth of thin semiconducting films is developed and implemented. The technique is based on analysis of the variation of ellipsometric parameters Ψ and Δ directly during the growth. The algorithm is tested in synthesis of Si/SiO₂/Si(100) and Hg_{1 ? x} Cd _x Te structures.     

Formation of one-dimensional crystalline silica on a metal substrate

We have observed formation of one-dimensional silica structures of 0.5 nm in width on Mo(1 1 2) single crystal surface. Combination of high-resolution scanning tunneling microscopy, photoelectron and infrared spectroscopy, and density functional theory provides strong evidence for formation of paired rows of corner sharing [SiO₄] tetrahedra chemisorbed on a metal substrate.     

The aeroballistic technique for studying sonic-boom characteristics

In the present paper, we analyze a suggestion implying the use of the aeroballistic technique for carrying out studies of shock-wave (sonic-boom) characteristics at large distances from the freely flying model. An analysis of the main engineering solutions ensuring the possibility of implementing the proposed experimental facility in the range of flight velocities of examined models from one to two Mach numbers is performed. A list of scientific and engineering problems pertaining to the study of sonic-boom characteristics in the middle and far zones which can be experimentally tackled with the help of the proposed facility is presented.     

Photon transmission technique for studying multiple phase transitions in a liquid crystal

A photon transmission technique was used to monitor the multiple phase transitions in a 4-butoxyphenyl4(')-declyoxybenzoate (BOPDOB) liquid crystal. Drastic decreases in the transmitted photon intensity (I) were attributed to the sequential phase transitions in BOPDOB upon cooling. In this paper, it is assumed that the order parameter rho is proportional to the transmitted photon intensity. The isotropic-nematic and nematic-smectic-A transitions were observed and found to be of first order. It was observed that the smectic-A-smectic-C and smectic-C-smectic-G transitions are second order. It was found that for the smectic-A-smectic-C transition, critical exponent crosses over from beta=0.513+/-0.006, which is consistent with mean-field theory, to beta=0.35+/-0.009, which is consistent with heliumlike behavior, as the Ginzburg criterion predicts. The critical exponent for the smectic-C-smectic-G transition was found to be beta=0.703+/-0.001. Transition temperatures were established at each phase transitions and found to be 84.92 degrees C, 74.85 degrees C, 52.96 degrees C, and 33.03 degrees C for isotropic-nematic, nematic-smectic-A, smectic-A-smectic-C and, smectic-C-smectic-G transitions, respectively.     

SRXRF microprobe as a technique for studying elements distribution in Elsholtzia splendens

Elsholtzia splendens is a copper tolerant plant growing in copper mine areas in south of China and accumulates considerable heavy metals in plant tissue. In this study, synchrotron radiation X-ray fluorescence spectroscopy (SRXRF) microprobe was used to study the Cu and other elements distribution in E. splendens. The element (P, S, Cl, K, Ca, Mn, Fe, Cu, Zn) in the leaf epidermis and cross-sections of the stem and leaf could be checked by SRXRF which was considered a sensitive technique for trace element analysis. The highest Cu levels were measured in the vascular tissues of stem and petiole, while Cu levels in mesophyll were higher than in leaf epidermis. The levels of most elements were not higher in trichomes than in other tissues. It seems that the celluar compartmentation of heavy metals in epidermis and epidermal trichomes was not the general feature of all plants. There was a significant correlation between Cu and P, S, Ca in distribution, which suggested P, S, and Ca played an important role in Cu accumulation of E. splendens. Based on the significant correlation between Cu and elements Mn, Fe, and Zn in distribution, it seemed that Cu, Mn, Fe, and Zn could be transported by the same transporters with a broad substrate range.     

Conduction model including some fundamental conduction mechanisms for a discontinuous metal film on a dielectric substrate

Presented is a method of describing electrical properties of discontinuous metal films. In this method, the film random areas are generated with the following parameters (determined by experiment): the coverage coefficient q and the log-normal distribution of the island diameter and interisland space (gap). A lattice is set on the film taking into account such microscopic conduction mechanisms as tunneling, metal conduction and dielectric conduction. It has been found that depending upon the coverage coefficient and the island diameter and interisland gap distribution, different conduction mechanisms may be dominant.     

Wetting and coalescence of the liquid metal on the metal substrate

Molecular dynamics(MD) simulations are performed to investigate the wettability of liquid metal on the metal substrate. Results show that there exists different wettability on the different metal substrates, which is mainly determined by the interaction between the liquid and the substrate. The liquid metal is more likely to wet the same kind of metal substrate,which attracts the liquid metal to one side on the hybrid substrate. Exchanging the liquid metal and substrate metal has no effect on the wettability between these two metals. Moreover, the study of metal drop coalescing indicates that the metal substrate can significantly affect the coalescence behavior, in which the changeable wettability of liquid metal plays a predominant role. These studies demonstrate that the wetting behavior of liquid metal can be controlled by choosing the suitable metal substrate.     

Thickness measurement for submicron metallic coatings on a transparent substrate by laser optoacoustic technique

A new nondestructive technique for determining the thicknesses of submicron metallic coatings on transparent substrates is developed. The technique is based on measuring the frequency dependence of the efficiency of thermooptical conversion on the thickness of a metallic film in the case of its contact with a transparent fluid. Experiments were conducted with three chromium coatings of different thicknesses (0.2, 0.3, and 0.6 μm) on quartz substrates. Two different experimental schemes were used: a direct scheme (laser radiation hits the film from the side of the substrate) and an indirect one (the laser action upon the film occurs from the side of the fluid). The film thickness is determined by approximating the experimental frequency dependences of thermooptical conversion efficiency by theoretical curves with the use of the least-squares method. The optoacoustic method can be used for determination of coating thicknesses in the range from 50 nm to 5 μm with an error of about 50 nm.     

Optical anisotropy as a technique for studying ultrafast phase transformations at solid surfaces

A new technique for testing long-range order in high-absorption anisotropic crystals has been developed using conversion of an incident p-(s-)wave to an s-(p-)wave due to optical anisotropy. The technique yields time-resolved measurements of parameters related to phase transformations in thin (10⁻⁶–10⁻⁵ cm) layers with a high resolution (10⁻¹² s). Using picosecond laser pulses and an “Agat” streak camera, the technique has been applied to an experimental investigation of melting and recrystallization kinetics at zinc and graphite surfaces. It was found that the process of melting takes less than 3 ps and the recrystallization time is about 100 ps. Zh. éksp. Teor. Fiz. 113, 2162–2173 (June 1998)     

Method for studying metal ion self-diffusion in some inorganic compounds

A method for studying metal ion self-diffusion in oxides (or other inorganic compounds) is described. The method involves oxidation of an appropriate metal to form a dense, single-layered scale of the lowest valent oxide (e.g. MnO on Mn). The specimen is then treated in high vacuum, and the evaporation of metal diffusing through the scale is measured. From the rates of metal diffusion/evaporation as a function of scale thickness information about the defect structure is obtained. The metal ion self-diffusion coefficient is determined from the rate of metal transport (evaporation) through a scale with known thickness. The requirements and limitations of the method are discussed. The use of the method is illustrated for Mn self-diffusion in MnO at 1100°C. The self-diffusion coefficient of Mn in MnO is proportional to the square root of the oxygen pressure, , in t MnO phase field near the MnO/Mn₃O₄ phase boundary. It is also tentatively concluded that the predominating defects near the Mn/MnO phase boundary are manganese interstitials.     

X-Ray Reflectometry of DMPS Monolayers on a Water Substrate

The molecular structure of dimyristoyl phosphatidylserine (DMPS) monolayers on a water substrate in different phase states has been investigated by X-ray reflectometry with a photon energy of ~8 keV. According to the experimental data, the transition from a two-dimensional expanded liquid state to a solid gel state (liquid crystal) accompanied by the ordering of the hydrocarbon tails C₁₄H₂₇ of the DMPS molecule occurs in the monolayer as the surface pressure rises. The monolayer thickness is 20 ± 3 and 28 ± 2 Å in the liquid and solid phases, respectively, with the deflection angle of the molecular tail axis from the normal to the surface in the gel phase being 26° ± 8°. At least a twofold decrease in the degree of hydration of the polar lipid groups also occurs under two-dimensional monolayer compression. The reflectometry data have been analyzed using two approaches: under the assumption about the presence of two layers with different electron densities in the monolayer and without any assumptions about the transverse surface structure. Both approaches demonstrate satisfactory agreement between themselves in describing the experimental results.     

Microwave Correlation Reflectometry for Tokamak CASTOR

A correlation reflectometer in 8-mm wavelength range has been constructed and installed on CASTOR tokamak. The reflectometer can operate on three fixed frequencies (29, 33, and 35 GHz). This is universal correlation sine-cosine reflectometer, which can work in poloidal or toroidal correlation regime and in ordinary mode (O-mode) and/or extraordinary mode (X-mode). A computational method of a direct evaluation of the phase fluctuations as well as absolute value of the phase from sine-cosine data has been developed. Using this method the relative plasma density fluctuations in the CASTOR core plasma has been determined in the range of few percent under assumption of parabolic density distribution.     

Ordered ultra thin ZnO films on metal substrate

Ultra thin ZnO films were prepared on metal Mo(1 1 0) substrate under ultrahigh vacuum conditions either by depositing Zn in 10⁻⁵ Pa oxygen or by oxidizing pre-deposited Zn films. The films were characterized in situ by various surface analytical techniques, including Auger electron spectroscopy, X-ray and ultraviolet photoelectron spectroscopies, low energy electron diffraction and high resolution electron energy loss spectroscopy. The results indicate that a long-range ordered and stoichiometric ZnO films are formed along its [0 0 0 1] direction. The annealing experiments show that as-prepared ZnO films are thermal stable until 800 K. This study provides constructive information to further understand the growth mechanism of ZnO films on different substrates.     

金属衬底上石墨烯的红外近场光学

对石墨烯/铜体系开展了系统性的近场光学实验研究,成功观测到了区别于铜衬底的、来自石墨烯的近场光学响应信号,发现在表面台阶几何参数相同的铜衬底上的不同石墨烯样品表现出了截然不同的近场光学响应.