利用俄歇电子能谱确定Au-Cu系统的互扩散系数及晶界扩散系数

本文利用俄歇电子能谱(PHI-550)测得了经过不同时间间隔热处理的Au-Cu系统中铜在金薄膜内的浓度剖面。根据铜的浓度斟面及Hall公式,我们使用了两种方法——“中心梯度法”及“平坦区上升法”计算出Au-Cu系统的互扩散系数以及晶界扩散系数。本文还对上述计算结果进行了讨论。     

PNN／PZT系梯度功能压电陶瓷离子互扩散动力学

研究了ＰＮＮ／ＰＺＴ系梯度功能压电材料中各类离子互扩散反应及其随温度和时间的变化。用电子探针测量了互扩散偶的组分分布，利用“薄板叠加”扩散模型，对Ｎｉ＾２＋、Ｎｂ＾５＋，Ｔｉ＾４＋和Ｚｒ＾４＋的扩散浓度分布曲线进行数值逼近计算，确定了互扩散层的厚度，估算了各离子的扩散系数及其表现激活能。     

Fe_2O_3/TiO_2扩散偶的固相反应

采用扩散偶的方法研究了Fe2O3和TiO2在1373K空气气氛不同时间下的固相反应。采用场发射扫描电镜对扩散偶表面形貌进行观察和线扫描能谱分析。根据线扫描能谱分析所得的组元扩散浓度曲线,用Den Broeder改进的Boltzmann-Matano法计算出Fe2O3/TiO2扩散偶的互扩散系数,结果发现互扩散系数与Fe3+浓度呈一定的线性关系,并随着Fe浓度的升高而增大,同时用空位扩散机理讨论了Fe2TiO5的形成。     

温度对抗菌涂层薄膜中Nisin扩散性能的影响

温度是影响抗菌涂层中抗菌剂扩散的重要因素。制备含相同浓度的乳酸链球菌素(Nisin)的抗菌涂层薄膜,在5,25和45℃下测量不同时间段涂层中扩散出的Nisin浓度,应用费克第二定律获得其扩散系数。结果表明:随着温度的升高,扩散系数也随之增大,并根据Arrhenius公式计算出活化能。     

铜在碳钢中扩散及其对碳钢耐腐蚀性的影响

用水溶液电沉积法在碳钢表面电镀铜并进行高温扩散退火,用Den-Broeder法计算铜在碳钢中的扩散系数,研究了铜在碳钢中的扩散行为及其对碳钢耐腐蚀性的影响。结果表明,铜在碳钢中的扩散主要沿晶界进行,铜的扩散抑制了热处理过程中碳钢晶粒的长大。铜在碳钢中的扩散系数为1.11×10-16～3.03×10-11 cm2/s,扩散系数随着退火温度的提高而升高,随着铜浓度的提高而降低。铜在碳钢高温奥氏体区中扩散所需的激活能为126～167 kJ/mol,在高于低温铁素体+奥氏体混合区中激活能为90～108 kJ/mol。通过铜在碳钢中的扩散制备的Cu-Fe梯度材料,具有优良的耐腐蚀性。     

Ti6Al4V合金双辉渗钼扩散系数的数值分析

以Ti6A14V合金双辉等离子渗钼的扩散行为为研究对象,针对具有沉积层和扩散层的典型钼合金化改性层的钼元素含量分布形态,采用数值分析方法计算了钼元素的扩散系数。结果表明:通过这种数值计算方法能较好地揭示Ti6A14V合金等离子渗钼的扩散行为,高钼浓度区域的钼扩散系数较小,而低钼浓度区域的钼扩散系数较大;不同沉积层的处理方法对钼扩散系数的计算结果影响显著。     

纳米沟道中离子扩散系数

提出了一种测量纳米沟道中离子扩散系数的新方法.该方法的原理是:首先测出纳米沟道两端之间溶液电阻的变化,推算出两端离子浓度的变化,然后运用有限扩散理论,计算出纳沟道中离子扩散系数.根据本文的扩散系数测试系统,成功测得一定浓度的KCl溶液在纳沟道中扩散系数.结果表明离子在纳沟道中的扩散系数小于在宏观沟道中的扩散系数的现象.并分析了双电层效应和尺寸效应对纳沟道中离子扩散的影响.     

NiCrAlYSi涂层与镍基高温合金基体互扩散行为研究

采用电弧离子镀方法在镍基高温合金DZ125上沉积NiCrAlYSi涂层,通过对不同氧化时间后Al和Cr原子浓度分布曲线的分析,运用Boltzmann-matano方法,计算了Al和Cr元素在1373K分别加热0.5,2h和5h的互扩散系数,并拟合了这三个时间段的计算结果.结果表明:相同温度下,Al和Cr的互扩散系数分别随Al和Cr的原子浓度增加而增大.随氧化时间的延长,Al的互扩散系数随原子浓度的变化先增大然后基本不变,Cr的互扩散系数则逐渐减小;伴随着元素间互扩散行为的增强,涂层中的Al和Cr向基体扩散,基体合金元素Ni,Co,Mo,Ti和W则向涂层扩散,但涂层中Mo和Ti的含量相对较少.由于元素间互扩散行为,涂层中各元素的含量将趋向于更加均匀.     

液态Pb-Cu合金结构与扩散性质的分子动力学模拟

通过分子动力学方法模拟液态Pb-Cu合金的熔体结构,得到液态合金的对相关函数曲线、配位数和相关半径,并用于分析合金熔体内部的结构。同时将NRTL方程与分子动力学方法结合,提出一种计算合金互扩散系数的新方法,使用该方法计算得到了Pb-Cu合金的自扩散与互扩散系数,并分析了熔体结构对合金扩散性质的影响。     

溴化锂水溶液分子扩散系数的理论求算

本文从电解质溶液理论出发,推导出了在任意温度与浓度条件下溴化锂水溶液的平均活度系数的计算表达式。将此表达式代入 Gorden 半经验公式,就得到了计算在任意温度与浓度条件下溴化锂水溶液分子扩散系数的计算公式。由该计算公式算出的溴化锂水溶液分子扩散系数,与T.Kashiwagi 等采用全息干涉法所测初步结果完全吻合,说明本文推导的公式(10)、(16)和(17)是可信的。     

Diffusion processes in the Au(111)/Ag(111) thin film system

The diffusion mechanisms of silver through Au(111) films 360 Å thick for different temperatures and heating times are studied. By means of quantitative Auger electron spectroscopy and in-depth profiling techniques the composition of the first monolayer and the composition profiles of diffused silver against time and heating temperature are determined. After elimination of instrumental effects the bulk silver interdiffusion coefficients for different temperatures and the activation energy of diffusion are obtained. The extrapolation stages allows the time required for the diffused onto the surface in the first diffusion stages allows the time required for the first appearance to be determined. Comparison with two standard expressions gives the corresponding grain-boundary diffusion coefficients and the activation energy. A numerical formalism, which includes the variation of composition at the interface but makes no allowance for grain boundary-grain diffusion, is tested esing the calculated coefficients. The agreement between the experimental results and the theoretical surface compositions is satisfactory within the limitations of the proposed model.     

Ion back-scattering analysis of interdiffusion in Cu-Au thin films

Helium ion back-scattering has been used to examine the interdiffusion behavior of the thin film copper-gold system. Techniques for distinguishing bulk diffusion and grain boundary diffusion using back-scattering are presented. At temperatures in the range 200°–500°C, the grain boundary diffusion mechanism is shown to predominate in Cu-Au thin films. The back-scattering results suggest a model in which interdiffusion takes place by very rapid saturation of the grain boundaries in the gold film by copper and a slower filling of the copper grain boundaries by gold. The atoms in the grain boundaries then diffuse into the grains by bulk diffusion. In the parent gold film, we suggest that the amount of Cu Au ₃ formed near the grain boundaries is uniform in depth. In the parent copper film, more Cu₃Au forms near the original Cu-Au interface than further into the copper film. No evidence was found to suggest the formation of a pure layer of CuAu₃ or Cu₃Au. The interdiffusion and compound formation process is found to be characterized by an activation energy of 1.35-1.5 eV.     

Interdiffusion and phase formation in Au/Sn thin film couples with special emphasis on substrate temperature during condensation

The interdiffusion of gold and tin thin films was studied, with special emphasis on the influence of the substrate temperature during evaporation. A special target chamber makes it possible to evaporate several films in succession and to analyse them by Rutherford backscattering at any stage in the interdiffusion process without exposing the specimens to the atmosphere. The samples can be kept at any temperature between -170 and +150°C during the evaporation, the heat treatment and the analysis. The interdiffusion of Au/Sn films is complex, with several competing processes going on at the same time. If the tin is evaporated at low temperatures, the initial stage of the interdiffusion will be dominated by grain boundary diffusion of gold into the tin film followed by diffusion into the tin grains, resulting in the formation of the AuSn₄ phase. The growth of the AuSn₄ phase was found to be linear with time. Concurrently the AuSn phase grows in a planar manner from the original interface. The thickness of this phase grows as t$\text{1}\text{2}$ and is believed to be limited mainly by the grain boundary diffusion of gold through the AuSn phase. This diffusion has an activation energy E_a = 0.59±0.06eV. When the substrate temperature during evaporation of the tin film is decreased, we observe an increase in the growth rate of the AuSn phase. This is believed to be caused by the decrease in grain size.     

Investigation of diffusional intermixing in Si/Co/Ta system by Secondary Neutral Mass Spectrometry

Low temperature analysis of diffusion and intermixing of Co-Si systems are very important in applications for microelectronics and Ultra Large Scale Integration (ULSI). In this communication a comprehensive report has been given on degradation and diffusion processes in the Si(substrate)/Co(150 nm)/Ta(10 nm) system. The samples were prepared by DC magnetron sputtering and were annealed in argon ambient at several temperatures ranging from 400 to 623 K for various times. The composition of the samples was investigated by Secondary Neutral Mass Spectrometry (SNMS). The degradation/intermixing starts with fast (grain boundary (GB)) diffusion of the Si into the Co layer. After some incubation time Si atoms appear and spread over the Co/Ta interface. This amount of Si accumulated at the Co/Ta interface acts as a reservoir for back-diffusion into the Co layer from the Co/Ta interface through the slower grain boundaries. At higher temperatures the formation of a Co-Si phase was detected at the Co/Si and Co/Ta interface. Three different diffusion coefficients were calculated from the SNMS concentration-depth profiles using “Central-gradient” (CG) and “First-appearance” methods. The observed intermixing was interpreted as a mixture of different “C-type” grain boundary diffusion processes. Furthermore, the experimental results are also compared with computer simulations modelling the grain-boundary diffusion through different grain-boundary paths. From the SNMS profiles measured at different temperatures the activation energy of the GB interdiffusion coefficients was deduced using the “CG method”.     

Observations on the electromigration in various thin films of group I–IV

The transport of ions under the influence of a direct current has been found to be directed towards the cathode in thin films of silver, copper and gold, and towards the anode in aluminum, magnesium, indium, tin and lead films. The direction of electromigration in silver, copper and gold films is opposite to the one usually found in bulk samples of these metals. In silver films with large as well as with small grains the direction of electrotransport is the same. The experiments show that electromigration in single-crystalline silver films is small. This suggests that grain boundary electrotransport predominates in silver films over surface and volume electrotransport, which is also true for aluminum films.     

An investigation of silver diffusion through gold films by Auger electron spectroscopy

Silver diffusion through gold films of different thicknesses was observed by Auger electron spectroscopy at room temperature. It was found that very thin enriched silver layers have occurred on gold films within one month after the evaporation of gold films on silver substrates. Some experiments for determining the effects of sulphur adsorption layers on the thin films are also reported.     

The effect of temperature and humidity on interdiffusion of gold and titanium in thin films

Gold-titanium thin films are frequently used in a number of devices where gold is the conductor and titanium the bonding agent between gold and glass or ceramic substrates. Exposed to the corrosive environments, gold-titanium metallizations deteriorate and lead to failure of the devices. In this work, a preliminary study, the effect of humidity and temperature on interdiffusion of gold and titanium films was investigated. It was found that during the initial exposure period of gold-titanium thin film samples, the electrical resistance decreased. This decrease of electrical resistance occurs at temperatures as low as 70° C and can probably be ascribed to annealing processes in the samples. Exposure of the samples to higher temperatures results in the diffusion of titanium along the grain boundaries of the gold to the surface of the sample and in an increase of electrical resistance. It was observed that at 325° C titanium diffuses from grain boundaries into the gold grains and forms a gold-titanium alloy. An addition of the water vapour to the agron atmosphere does not noticeably affect the diffusion process. Optical microscope observations, of the titanium diffusion to the sample surface were confirmed by scanning electron microscopy and by X-ray fluoroscence counts in a scanning electron microscope.     

Low temperature interdiffusion in the Au-Pd and Au-Rh thin film couples

Interdiffusion profiles in thin polycrystalline multilayer films of Pd-Au and Ti-Rh-Au at temperatures up to 490°C have been measured by Rutherford backscattering. Room temperature grain boundary diffusion of Au into Rh was observed and analyzed to give D_B = 3.5 × 10^-17 cm² sec^-1. The Whipple analysis is applied to our data for the diffusion of Au in Pd; using the lattice diffusivity of Neukam, an activation energy for grain boundary diffusion of 0.9 eV is found. The diffusion of Pd in Au has also been analyzed using the Whipple model, which gives a grain boundary activation energy of 0.6 eV.     

The effect of electrode films on the electrical resistance of thin tin films

The variation in resistance of thin films of tin deposited onto glass substrates was studied using pre-deposited gold, silver, aluminum and tin electrodes. The percentage variation in resistance of the tin films was found to be different for the different electrode materials. The structural features of the tin-electrode film junctions were investigated using optical and scanning electron microscopes. The difference between the variations in resistance with time for different electrode films is explained on the basis of interdiffusion, alloy formation and oxidation at the electrode film junctions.