The Ti/c-Si solid state reaction I. An ellipsometrical study

This paper is the first of a series of three articles in which we present the results and analyses of an extended study of the c-Si/Ti solid state reaction. In this paper we will discuss the spectroscopic ellipsometric investigation. Thin (≈10nm) Ti films are grown on clean Si(111) surfaces and are subsequently heated. The Si indiffusion and the Si-Ti intermixing are continuously registered by three-wavelengths ellipsometry. Two metastable intermediate phases are observed to form before the final state is obtained Spectroscopic ellipsometry (E = 2−4.5 eV) is used to characterize the as-deposited layer, the metastable intermediate phase and the final state. Analysis of these spectra shows that: (1) Si and Ti intermix during the initial Ti deposition, (2) a fast reordering of the Ti atoms occurs when the system is slightly heated (≈175°C), (3) a metastable, probably monosilicide phase with a large Si concentration gradient is obtained at ≈350°C, (4) a homogeneous metastable TiSi₂ forms at ≈450°C, at ≈700°C a roughened TiSi₂ layer with a surplus of c-Si is formed.     

The Ti/c-Si solid state reaction : II. Additional measurements by means of RBS, XPS and AES

In a previous paper [Appl. Surface Sci. 40 (1990) 333], we have reported the results of a spectroscopic ellipsometric study of the c-Si/Ti solid state reaction. For this purpose we have grown and heated thin (≈10nm) Ti films on a clean c-Si substrate. The investigation revealed that already at moderate temperatures a metastable silicide (≈350°C), probably a monosilicide, and disilicide (≈450°C) are formed. These two metastable transition states, denoted by state I and II respectively, and the final disilicide (state III, ≈700°C) are additionally studied by means of a number of quantitative techniques, such as RBS, XPS and AES. The results reveal a Si-enriched monosilicide state I, Si: Ti = 1.2 and a stoichiometric but Si segregated disilicide state II; surface composition approximately TiSi₃. The finally obtained disilicide (III) has recrystallized into probably large, flat islands embedded in a c-Si matrix.     

The solid state reaction between AgI and HgI2

The kinetics of the solid state reaction between AgI and HgI₂ is investigated experimentally by measuring the thickness of the layer of the α-Ag₂HgI₄ product phase as a function of the annealing time and the reaction temperature. A theoretical expression is derived which allows the calculation of the variation of the chemical potentials of the binary components across the product layer considering the variation of the product phase composition. A value of A₀ = 6 kJ/mol is estimated for the standard affinity for the formation of stoichiometric Ag₂HgI₄ from the binary components AgI and HgI₂.     

Dielectric spectroscopy on the kinetics of solid state reactions

Solid state reactions can be investigated by a great number of methods. Most of these, disturb the reaction system under test since they require either taking samples for chemical analysis or unbalancing the system thermally. Measurements on suitably chosen physical parameters may serve as useful tools for avoiding such problems. It is shown in this paper that dielectric spectroscopy is a good means for analysing solid state reactions of ion conductors. We have carried out measurements on the reaction 2AgI+HgI₂ → Ag₂HgI₄ obtaining results which clearly allow the exact determination of the overall reaction's time dependence and the product conductivity. However, there is some more investigation necessary in order to evaluate individuals constants describing the product growth and initial product decrease separately. Nevertheless first ideas can be discussed on the basis of our results.     

NMR study of solid state reaction in Co-Sn multilayers

Amorphization by solid state reaction at room temperature in Co-Sn multilayers with periodicities of 65, 130 and 195 Å and relative Co to Sn ratio varying as 4, 3, 2 has been studied by zero field NMR method. The distribution of⁵⁹Co hyperfine fields and that of NMR enhancement factors were used as a probe of the ferromagnetic part of a sample and its evolution with the annealing time. The critical role of the interface during the first hours of annealing is pointed out. On the long time scale the diffusion process is slowed down by the creation of Kirkendall voids and after 3 months of annealing some crystalline Co is still present.     

Synthesis of earth-abundant Cu2SnS3 powder using solid state reaction

Cu₂SnS₃ (CTS) powder has been synthesized at 200 °C by solid state reaction of pastes consisting of Cu and Sn salts and different sulphur compounds in air. The compositions of the products is elucidated from XRD and only thiourea is found to yield CTS without any unwanted CuS_x or SnS_y. Rietveld analysis of Cu₂SnS₃ is carried out to determine the structure parameters. XPS shows that Cu and Sn are in oxidation states +1 and +4, respectively. Morphology of powder as revealed by SEM shows the powder to be polycrystalline with porous structure. The band gap of CTS powder is found to be 1.1 eV from diffuse reflectance spectroscopy. Cu₂SnS₃ pellets are p-type with electrical conductivity of 10⁻² S/cm. The thermal degradation and metal–ligand coordination in CTS precursor are studied with TGA/DSC and FT-IR, respectively, and a probable mechanism of formation of CTS has been suggested.     

Transformation kinetics of A-15 superconductors formed by solid state reactions

Various fabrication processes devised for making multifilamentary A-15 super-conductors are all based on solid state reactions, transforming the host metal into the binary A-15 phase. The kinetics of the growth process involved in the compound formation form the theme of this paper.     

Synthesis of indium oxide nanoparticles by solid state chemical reaction

A three stage process consisting of mechanical milling, heat treatment, and washing has been investigated as a means of manufacturing nanoparticulate powders of In₂O₃. In the first stage of processing, mechanical milling was used to prepare a nanocrystalline mixture of In₂(SO₄)₃, Na₂CO₃, and NaCl. Subsequent heat treatment of the milled reactant resulted in the formation of nanocrystalline In₂O₃ particles embedded within a matrix of Na₂SO₄ and NaCl. In the final stage of processing, the In₂O₃ powder was recovered by washing with deionised water. The duration of milling was found to determine the degree of hard agglomeration in the final washed powder. It was also found that the average particle size of the powder could be controlled between 8 and 18 nm by simply varying the temperature of the post-milling heat treatment over the range of 400 to 550°C. These results demonstrate that solid state chemical reaction can be used as a technically simple method for manufacturing nanoparticulate In₂O₃ powders with a controlled particle size and low levels of hard agglomeration.     

Hyperfine interactions in solid state reaction of hematite with aluminium

The solid state reaction of hematite with aluminium has been induced by mechanical alloying. Mössbauer spectroscopy and X‐ray diffraction have been used to investigate the reaction products. The reaction was completed in a time longer than 15 min but shorter than 30 min. During the reaction a Fe(Al) bcc solid solution was obtained as a matrix, with Al₂O₃ as reinforcement. After prolonged milling both components were in a nanocrystalline paramagnetic state.     

钛－镍－硅固相反应形成的镍硅化物/n-硅(100)接触的I-V-T研究

在不同退火温度下，有一薄层钛覆盖层的镍－硅经过固相反应生成了镍硅化物/n-硅(100)接触，研究了其在80K到室温的电流－电压（I-V）特性。低温I-V曲线在低偏压区的电流显著地比传统的热电子发射（TE）模型预计的要大。用基于Tung的夹断模型简化得到的双肖特基势垒模型分析了实测的I-V曲线，从中可以得到肖特基势垒不均匀性的量度。较高温度退火导致较大的势垒不均匀性，意味着硅化物薄膜均匀性的变坏。钛覆盖薄层可以稍微提高硅化镍的相转变温度，以及形成的一硅化镍的热稳定性。     

Proton irradiation and solid state reaction of Fe−Zr multilayers

The amorphization of Fe−Zr multilayers due to ion-beam mixing and solid state reaction is studied in detail using the CEMS and CXMS. The nature of the amorphous Fe−Zr phase produced by both processes is the same suggesting that diffusion of Fe is an important mechanism during ion-beam mixing.     

Amorphization of crystalline Co and Sn multilayers by solid state reaction

Co_xSn_1?x amorphous alloys have been formed by solid state reaction at room temperature, from polycrystalline multilayers of Co and Sn deposited at 77 K. The forming ability range, temperature variation of the resistance, crystallization temperature of the amorphous alloys obtained by this new technique are very similar to those of amorphous Co_xSn_1?x alloys formed by vapour quenching.     

Ferromagnetism of Ni cluster in Ni-doped ZnO by solid state reaction

Ni-doped ZnO samples with ferromagnetism at room temperature have been prepared by solid state reaction. It is found that the ferromagnetism originates from the nanosized Ni clusters formed from the decomposition of NiO during calcination. The magnetic properties can be explained by the microstructure of sparsely distributed, randomly oriented and magnetically saturated Ni clusters. Experiments show that the addition of Cu ions will block the decomposition of NiO because Cu²⁺ is more likely reduced to Cu⁺. Hall effect confirms the absence of exchange coupling between local spins and charge carriers.     

Impurity effects and reaction kinetics of the pressure-induced α → ω transformation in Ti

The effects of impurities on the transformation pressure and the reaction kinetics of α → ω transformation in Ti metal were studied by the electrical resistivity technique upto a pressure of 80 kbar. The ω-start pressure is found to be lowered when the soaking time was varied from 3 to 10 min. Under identical (viz. 10 min) soaking conditions, the ω-start pressure varied from 29 to 60 kbar, following the increase in oxygen content and other impurity levels in the samples. After the onset of ω, the increase in electrical resistance with time under isothermal-isobaric conditions is typical of that of an isothermal martensite.     

固态阴极射线发光的发现

通过分层优化方案,采用有机场致发光材料,发现了一种新的激发发光方式,即固态阴极射线发光（solid state cathodoluminescence,简称SSCL）,文章主要介绍了固态阴极射线发光的发现历史、发光现象的辨认、发光现象的普适性考察以及其良好的发展前景.     

Synthesis of Cu2ZnSnSe4 compound powders by solid state reaction using elemental powders

The solid state reaction method was used to synthesize single phase and near stoichiometric Cu₂ZnSnSe₄ compound from elemental Cu, Zn, Sn and Se powders in a quartz tube furnace under an Ar flow at atmospheric pressure. These elemental powders were initially milled using zirconia balls. The α-CuSe phase was present in all of the milled powders because of the mechanical alloying effect between the Cu and Se powders. The solid state reaction mechanism was examined for the synthesis process. The phase analysis suggested that the Cu₂ZnSnSe₄ powder crystallized into the stannite phase with a high degree of crystallinity after near stoichiometric molar ratios of the powders was reacted at 500 °C for 6 h. This study showed that the solid state reaction method was a straightforward technique for the synthesis of the Cu₂ZnSnSe₄ compound powders from the elemental powders.     

Structural and electrochemical behavior of tungsten oxide obtained by solid state reaction

Tungsten oxides have been used successfully as intercalation compounds of high performance batteries. In this communication we present a new and innovative route to obtain orthorhombic WO₃ where the crystallographic structure can be carefully controlled. X-ray diffraction data indicates that a texture is obtained in the [0k0] direction, whereas XPS suggests that the valence of the tungsten atom is + 6. The electrochemical behavior of the oriented sample was studied by chronopotentiometry and its charge–discharge capacity was evaluated. The results showed stable values close to 100 mA h/g after the 70th cycle, which compares favorably to the best know WO₃ compounds produced so far.     

Cation self-diffusion in LaFeO3 measured by the solid state reaction method

Cation diffusion in LaFeO₃ has been studied using the solid state reaction between sintered bodies of La₂O₃ and Fe₂O₃ at 950–1350 °C in air or O₂–N₂ mixtures. LaFeO₃ was the only product formed. The growth was parabolic and demonstrated to take place predominantly by diffusion of Fe³⁺ through the LaFeO₃ layer. The self-diffusion coefficient of Fe³⁺ was accordingly calculated from the parabolic rate constant, and at constant activity of La₂O₃, a_La2O3 = 1, it shows Arrhenius-type behaviour with activation energy 320 ± 20 kJ/mol. It appeared to be independent of the surrounding pO₂, but this was ascribed to lack of equilibrium with the atmosphere during growth of the LaFeO₃ layer. Correspondingly, the product LaFeO₃ is probably stoichiometric, and differences between our diffusivity and activation energy and those in the literature are discussed in view of this.     

INADEQUATE-CR experiments in the solid state.

Through-bond connectivity can be probed by J couplings. For effective two-spin systems, the INADEQUATE experiment is highly valuable in liquid-state spectroscopy. It is the purpose of this Communication to show that in-phase INADEQUATE-CR spectra, where the intensity is concentrated in only one line of the J splitted doublet, can be obtained from solid-state samples. The problem of the cancellation of nonresolved multiplet lines, as experienced typically in INADEQUATE spectra in the solid, is resolved and the (13)C spectra become simpler because the number of resonance lines is reduced. Furthermore, a gain in signal intensity by 2 can, theoretically, be achieved. We limit the discussion to two-spin systems. In the present context, a two-spin system is defined considering the J coupling only. When the dipolar coupling is also taken into account, the two-spin system will usually become a many-spin system, but in the present context this is not relevant.