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Material Sciences 2021
超薄合金薄膜表面与界面偏析宏观与微观模型的比较
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Abstract:
本文通过比较基于宏观热力学参数的修正达肯模型(Modified-Darken model)和基于微观原子间相互作用参数的规则溶液断键模型(Regular solution broken bond-type model)，将偏析热力学参数与原子间相互作用参数建立了直接的关联。修正达肯模型中的偏析能可表示为原子在表面/界面与体层之间的键能之差，而规则溶液断键模型中不同原子间的键能可通过修正达肯模型中的相互作用系数获得。修正达肯模型可描述从块体到超薄膜表面与界面动态和平衡态的偏析，而规则溶液断键模型则可描述应力作用下薄膜表面与界面平衡态的偏析。在修正达肯模型中引入应力项，可以更完美地描述合金薄膜材料中的偏析。利用修正达肯模型拟合偏析实验数据，获得的热力学参数可以用于检验规则溶液断键模型中原子间相互作用能的可靠性。本文以Cu-Al超薄合金属薄膜为例，分析了应力、薄膜原子间相互作用系数以及薄膜原子与衬底原子间相互作用对偏析的影响。
By comparing the Modified-Darken model with the macroscopically thermodynamic parameters and the regular solution broken bond-type model with the microscopically atomic interaction parameters, the direct correlation between the thermodynamic parameters and the atomic interaction parameters is clearly presented. The segregation energy in the modified Darken model could be expressed by the difference of the atomic band energy between the surface/interface and the adjacent bulk layers, while, the band energy of different atoms in the regular solution broken bond-type model could be obtained from the interaction parameter in the modified Darken model. The modified Darken model is often used for describing both equilibrium and kinetic surface segregation in both bulk and film materials, while, the regular solution broken bond-type model could be used for describing the equilibrium surface and interface segregation in under-stressed thin films. By introducing the additional stressed terms in the modified Darken model, the segregation in an alloy film could be perfectly described. By fitting the measured segregation data using the modified Darken model, the corresponding thermodynamic parameters (segregation energy and interaction parameter) could be obtained and be used for verifying the atomic interaction parameters used in the regular solution broken bond-type model. As an example, the equilibrium surface segregation in ultrathin Cu(111)-5at%Al alloy film is simulated by the two models and the results are compared in terms of stress and interaction parameter of the film atoms, the atomic interaction parameters between the film atoms and the substarte atoms.
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