高温碳离子注入形成碳化硅埋层的结构研究

采用离子束合成法,将p型(100)单晶硅衬底加热并保持在700℃的条件下分别进行剂量为8.0×1017cm-2和9.0×1017cm-2的C+注入,随后在氩气保护下经1250℃退火5h后形成β-SiC埋层。借助红外反射光谱、卢瑟福背散射能谱以及高分辨透射电镜等测试手段,对退火前后碳化硅埋层的组分及结构进行了表征分析,结果证明形成的碳化硅埋层结晶质量较好,并与硅衬底呈良好的外延关系。     

不同能量氮氧共注入形成的多层SOI结构

将氮和氧离子在不同能量下依次注入于硅片,并经1200oC,2h高温退火后,形成具有含有中间硅层的夹心埋层SOI结构。对该样品做俄歇电子能谱(AES)、剖面透射电镜(XTEM)、二次离子质谱(SIMS)和击穿场强等测试,表明退火后形成具有Si-N-O、Si和Si2O夹心埋层的SOI结构。其击穿场强最大为5×106V/cm,与普通剂量SIMOX的相当。测试还发现氮在界面处有明显的富集效应,而且其在前界面的富集行为明显大于其在后界面的。     

Formation of thin SiO2 films by high dose oxygen ion implantation into silicon and their investigation by IR techniques

The ion dose dependence of the infrared transmission spectra of SiO₂ layers formed by high dose ion implantation into silicon was investigated for ion doses ranging from $\text{10}{}^{16}\text{to}\text{2 × 10}{}^{18}\text{(}{}^{16}\text{O}{}_2\text{)}{}^{\mathrm{+}}\text{30}\text{kV ions cm}{}^{-2}$. The annealing temperature dependence of these spectra is also reported.The passivation properties of the SiO₂ layers and their dependence on annealing were investigated and monitored by IR techniques. It was found that an SiO₂ layer that is formed by implantation with 1 × 10¹⁸ ions cm^-2 and annealed at temperatures higher than 550 °C but not more than 800 °C is similar in its IR and passivation properties to thermally grown SiO₂ films.     

Formation of functional layers on titanium alloys under nonstattonary conditions

We formulate basic thermodynamic ideas concerning the relationship between the physicochemical processes and the accumulation of defects in materials. The accumulation of damage results in, generally speaking, nonstadonary conditions of interaction in the metal-medium system. To describe the kinetics of the processes of high-temperature interaction of binary alloys with gaseous media, we formulate the corresponding initial-boundary-value diffusion problem and obtain analytic expressions for the distributions of impurity and alloying elements, for the thickness of the newly formed phase, and the increment of mass. We also perform the verification of the proposed approach. The numerical solutions adequately reflect the observed tendencies in the behavior of the parameters of corrosion of OT4 alloy in oxygencontaining media under the conditions of thermal cycling and static loading. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 36, No. 2, pp. 65–75, March-April, 2000.     

Structurally perfect silicon layers produced on sapphire by oxygen ion implantation

We demonstrate that the structural perfection of silicon layers on sapphire can be improved through high-temperature solid-state recrystallization after preamorphization of the most imperfect silicon layer near the silicon/sapphire interface by high-energy oxygen ions, followed by high-temperature recrystallization in an inert atmosphere.     

The formation of SiO2 films on silicon by high dose oxygen ion implantation

High dose oxygen ion implantation into silicon at 30 keV was performed to produce SiO₂ surface layers.The oxygen profile, stoichiometry and volume swelling were studied by Rutherford backscattering at doses of up to 2 × 10¹⁸cm^?2 and for various current densities. The surface structure and lateral homogeneity of the inslation properties were investigated by scanning electron microscopy and the liquid crystal technique respectively. By means of current-voltage and capacitance-voltage measurements the electrical properties of the layers produced were determined.A qualitative model of the formation of SiO₂ during high dose oxygen implantation into silicon is proposed. Blistering caused by implantation at high current densities leads to oxygen losses and to conductive channels in the dielectric layer. Except for their interface properties the SiO₂ films produced are comparable with thermal oxides.     

HI-ERDA, Micro-Raman and HRXRD studies of buried silicon oxynitride layers synthesized by dual ion implantation

Silicon oxynitride (Si_xO_yN_z) buried insulating layers were synthesized by dual implantation of nitrogen (¹⁴N⁺) and oxygen (¹⁶O⁺) ions sequentially into single crystal silicon in the ratio 1:1 at 150 keV to ion-fluences ranging from 1 × 10¹⁷ to 5 × 10¹⁷ cm⁻². Heavy ion elastic recoil analysis (HI-ERDA) studies of as implanted samples show Gaussian like distributions of nitrogen and oxygen. After annealing at 800 °C, both the nitrogen and oxygen distributions appear as flat plateau like regions near projected range showing the formation of a continuous buried oxynitride layer. Micro-Raman study of as implanted samples shows a broad peak at 480 cm⁻¹ for all fluences. It signifies a complete amorphization of silicon due to high fluence implantation. The annealing at 800 °C results in the reduction of the intensity of the broad peak observed at 480 cm⁻¹ and also gives rise to an additional peak at 517 cm⁻¹. It shows partial recrystallization of damaged silicon due to annealing. The X-ray rocking curves studies from high-resolution X-ray diffraction (HRXRD) of the samples implanted with different fluences have also further confirmed partial recrystallization of damaged silicon on annealing.     

Creep life extension of high temperature components under wall thinning conditions

Current methods of life extension of high temperature components have been examined. Importance of changing section size as a result of corrosion and erosion has been emphasized. A simple method based on the influence of service exposure on rupture strength of the material and the data collected on loss of section size during routine shut-down of plants has been suggested. Highlights of the computer software developed to assist such an exercise have been discussed. The outputs have been shown to compare fairly well with the results reported in literature.     

Flow properties of thermally insulating powders under different atmospheric conditions

We determined the flow properties of powders used as thermal insulative materials at different temperatures, pressures and moisture conditions. The powders used in this study, SiO₂-aerogel, precipitated and fumed silica, have primary particle sizes ranging from a few nanometers to hundred micrometers. Due to the porosity of the particles and/or their large interparticular forces compared to their weight, the powders have very low densities (about 100 kg/m³). Therefore they display very small solid thermal conductivities in the order of 1 to 2 · 10^х W/(m K) and thus are promising as evacuated thermal insulants. In addition these powders are resilent to external loads. A prerequisite for the use of these powders in technical applications is the determination of their flow properties. For this purpose the powder samples were filled into a stainless steel hopper and the flow rate through the bottom opening was measured using a balance. Simultaneously, the resulting angle of repose was determined. The hopper can be heated up to 200^°C to remove adsorbed water and gases from the inner surface of the powder. The measuring device was mounted into a vacuum chamber in order to determine the influence of atmospheric humidity or gas pressure (pressure variation from 30 to 10⁵ Pa).     

Spectroscopy of SiSiOx type samples prepared by oxygen implantation and processing under high pressure

The hydrostatic pressure-induced effect on the massive creation of “new” defects in CzSi with oxygen-related defects introduced by implantation of oxygen (at E?200 keV and doses D?1×10¹⁸ cm⁻²) and subsequent processing at up to 1500 K, is investigated in this work. The diamond anvil cell method (DAC) allows to carry out in situ investigations of structure, phase transitions and properties at high pressures (HP). Such a device was used for obtaining experimental absorption spectra of SiSiO_x sample in the DAC at hydrostatic pressure up to 20 GPa.     

Diamond formation from glassy carbon under high pressure and temperature conditions

The process of the formation of diamond from the glassy carbon with its characteristic bond nature was investigated in the diamond stable region at high pressures (up to 10 GPa) and temperatures (up to 3000° C), without any intentional addition of metals as solvent. The process of diamond formation was found to obey Ostwalds's step rule as follows: amorphous glassy carbon crystallized to form fully well-crystallized graphite prior to diamond formation and then the graphite crystals were converted to diamond by further heat treatment at pressures above 9 GPa. The many trigons formed are considered to be essentially a record of growth failure in the growth period. As a result of heat treatment for a longer time and/or at a higher temperature close to the diamond—graphite stability boundary, the diamond tended to grow with the (111)-face composed of the thin growth layers.     

Amine promoted, metal enhanced degradation of Mirex under high temperature conditions

In this study, zero-valent metal dehalogenation of mirex was conducted with amine solvents at high temperatures. Mirex was treated with excess amine in sealed glass tube reactors under nitrogen. The amines used were n-butyl amine (l), ethyl amine (l), dimethyl amine (g), diethyl amine (l), triethyl amine (l), trimethyl amine (g) and ammonia (g). The metals used were copper, zinc, magnesium, aluminum and calcium. The most suitable amine solvent and metal were selected by running a series of reactions with different amines and different zero-valent metals, in order to optimize the conditions under which complete degradation of mirex takes place. These dehalogenation reactions illustrated the role of zero-valent metals as reductants, whereas the amine solvents acted as proton donors. In this study, we report that mirex was completely degraded with diethyl amine (l) in the presence of copper at 100 degrees C and the hydrogenated products accounted for more than 94 of the degraded mirex.     

低能低剂量注水形成SOI结构材料的研究

采用无质量分析器的离子注入机，以低能量低剂量注水的方式替代常规SIMOX注氧制备SOI材料，测试结果表明，此技术成功地制备了界面陡峭，平整，表层硅单晶质量好的SOI结构材料，在剂量一定的条件下，研究不同注入能量对SOI结构形成的影响，使用剖面透射电镜技术（XTEM）和二次离子质谱技术（SIMS）等测试方法对注入样品和退火后样品进行分析，结果表明，表层硅厚度随注入能量增大不断增大；埋层二氧化硅厚度相对独立，仅在超低能（50keV)低剂量情况下厚度出现明显降低；埋层质量（包括界面平整度，硅岛密度等）与注入能量变化相关。     

Synthesis and crystallographic study of Pb-Sr hydroxyapatite solid solutions by high temperature mixing method under hydrothermal conditions

The solid solutions in the system of Pb and Sr hydroxyapatite, Sr_10−xPb_xHAp (x = 0-10), were successfully synthesized by high-temperature mixing method (HTMM) at 160 °C for 12 h under hydrothermal conditions. The samples were characterized by X-ray diffraction, chemical analysis and electron microscopic observation, and the site of the metal ions in the solid solutions was analyzed with the Rietveld method. The lattice constants, both a and c, of the solid solutions varied linearly with Pb content. It was found that Pb ions in the solid solutions preferentially occupied the M(2) site in the apatite structure. HTMM gives Sr-Pb HAp solid solutions much better crystallization. However, due to the formation of intermediate compound of Pb₃O₂(OH)₂ in the Pb(NO₃)₂·4H₂O solution before mixing with (NH₄)₂HPO₄ solution at 160 °C, HTMM causes the decrease of crystallization of the samples with high Pb content.     

Modelling of high temperature fatigue crack growth in Inconel 718 under hold time conditions

Inconel 718 is a frequently used material for gas turbine applications at temperatures up to 650 °C. The main load cycle for such components is typically defined by the start-up and shut-down of the engine. It generally includes hold times at high temperatures, which have been found to have a potential for greatly increasing the fatigue crack growth rate with respect to the number of load cycles. However, these effects may be totally or partly cancelled by other load features, such as overloads or blocks of continuous cyclic loading, and the actual crack propagation rate will therefore depend on the totality of features encompassed by the load cycle. It has previously been shown that the increased crack growth rate found in hold time experiments can be associated with a damage evolution, where the latter is not only responsible for the rapid intergranular crack propagation during the actual hold times, but also for the increased crack growth during the load reversals. In this paper, modelling of the hold time fatigue crack growth behaviour of Inconel 718 has been carried out, using the concept of a damaged zone as the basis for the treatment. With this conceptually simple and partly novel approach, it is shown that good agreement with experimental results can be found.