Quantitative characterization of chaotic instabilities in semiconductors

A method for quantitative characterization of chaotic dynamical systems is discussed. An electronic instrument for determining the number of independent variablesk ^*, involved in the motion, is described. It allows one to obtain these in real time from a single observable. The suggested technique has been applied to quantification of strange attractors underlying chaotic instabilities in semi-insulating GaAsCr, and n-Ge, irradiated with high energy electrons. In n-Ge, for instance, the measured numbersk ^* range from 2 to 4 depending on control parameters. These measurements reveal the highly deterministic nature of the observed chaotic oscillations. The physical mechanisms responsible for the current instabilities and chaotic behaviour are discussed.     

Thermal coefficient of linear expansion of non-crystalline chalcogenides in the As-S-Se-Te-I system

The object of the paper is an investigation of the glasses of the (As₂S₃)_x(AsSe_0.5Te_0.5I)_100-x. type for 65≤;x≤;95, using methods of thermomechanical analysis. Values of the thermal coefficients of linear expansion in solid and visco-plastic phase were determined. it was shown that introducing arsenic-sulfide in glass-matrix AsChI, i.e. (AsSe_0.5Te_0.5I), leads to an increasing stability of these glasses. The characteristic temperatures of softening Tg and the temperature of the beginning of deformation t_w increase by increasing content of As₂S₃. The analytical forms of dependence of four significant physical values α_g, α_l, Tg, Tw, as a function of As₂S₃ content in the structure of glasses were fitted. This revised version was published online in July 2006 with corrections to the Cover Date.     

FTS-20E富里叶红外光谱仪数据系统改造

报道了ＦＴＳ－２０Ｆ富里叶红外光谱仪数据系统改造的工作采用ＩＢＭ４８６计算机及新的数据接口取代了陈旧的ＮＯＶＡ４数据系统，文章详细描述了其硬件设计和软件编辑，改造不仅更新了ＦＴＳ－２０Ｅ里叶红外光谱仪，而且还使其达到９０年代的水平。     

Concentration and clean-up of trace hydrocarbons from atmospheric particulate matter

Summary The aim of this work is to establish the best conditions for concentration and purification steps in the trace analysis of aliphatic and polycyclic aromatic hydrocarbons (PAH) from atmospheric particulate matter by gas chromatography-flame ionisation detection (GC-FID) and high performance liquid chromatography with ultraviolet and fluorescence detection (HPLC-UV-FL). The best results for the more volatile compound were obtained with a combination of rotary evaporation and a stream of nitrogen (near to 100% for aliphatic hydrocarbons and from 70 to 105% for PAH). Two types of solid phase extraction (SPE)cartridges (Supelclean ^tm LC-Silica SPE tubes and Sep-Pak^? Plus silica cartridges) and glass column were examined for the purification and fractionation step. Blank chromatograms of both types of cartridges analysed by GC-FID made this study difficult, because a PSS (programmed split-splitless) injector was employed thereby increasing the sensitivity. This problem was not observed in the HPLC-UV-FL blank chromatograms of these cartridges. Glass columns filled with silica and alumina were chosen because no interference was found in the GC-FID blank chromatograms and the best recoveries in the fractionation of both aliphatic hydrocarbons and PAH were achieved. This is especially important when aliphatic hydrocarbons concentrations are lower than 1 μg mL⁻¹. Finally, the selected conditions were applied to the analysis of hydrocarbons in real atmospheric particulate samples.     

Phase Analysis of the Binary System of Cryolite (Na3AlF6) and Sodium Metasilicate (Na2SiO3)

The phase analysis of cryolite (Na₃AlF₆) and sodium metasilicate (Na₂SiO₃) was performed by thermal analysis. The eutectic system with a region of two immiscible substances at a concentration of Na₂SiO₃ between 42.8 and 46.3 mol‐% was identified and the eutectic temperature determined to (886±2) °C. Based on the results of mass‐loss measurements, it was assumed that the introduced Na₂SiO₃ reacts with Na₃AlF₆ due to the formation of some nonvolatile stable compounds. The stable reaction products were identified by X‐ray diffraction analysis and IR spectroscopy of the spontaneously cooled samples, which established the formation of NaF and stable amorphous aluminosilicate compounds.     

Multilayered Cu–Ti deposition on silicon substrates for chemiresistor applications

Abstract

On the perspective to develop CuO–TiO₂ MOS, multilayered Cu and Ti thin layers were alternatively deposited on silicon wafers using 25?keV Ar?+?ion beam sputtering and, subsequently, oxidized by thermal annealing in air at 400?°C for 24?h. The deposited films have variable ratios of the Cu and Ti % at. One of the main goal is to obtain such multilayers avoiding the presence of Cu–Ti–O compounds. The samples were characterized in terms of composition (by RBS and SIMS analyses) and morphology (by AFM and SEM investigations). In particular, SIMS maps allows to observe the spatial distribution and thickness of each phase of the Cu/Ti multilayers, and further to observe Cu diffusion and mixing with Ti, as well as phase separation of CuO and TiO₂ in the samples. The reasons of this effect represent an open issue that has to investigated, in order to improve the MOS fabrication.