Using Metallic Interlayers to Stabilize Metal-Metal Interfaces

技术：本研究的目的是研究超薄金属中间层在薄膜结构中稳定金属-金属界面的潜力。实验观察和模型计算的紧密结合用于识别那些当在界面上以单层数量沉积时可能在系统中形成稳定的外延界面的金属，否则以相互扩散和无序为特征。与表面活性剂不同，层间材料保留在界面上，以提高化学、热和结构稳定性。与传统的扩散屏障不同，中间层应该是原子薄的，以尽量减少对器件任何电子特性的影响。基于量子近似技术（BFS方法）的简单模型计算可以根据所研究的薄膜-衬底组合来指导层间材料的选择。实验观测用于扩展BFS参数数据库，从而改进模型。将层间概念扩展到工业过程中典型的溅射薄膜，也进行了研究。利用高能离子后向散射和通道、低能电子衍射、低能离子散射和x射线光电子衍射表征了界面上有序生长或相互扩散的程度。核能级光电子结合能用于识别界面上的化合物形成。非技术性：这项活动的智力价值源于对金属-金属界面合金形成的理解所取得的预期进展，特别是使用金属中间层来提高薄膜器件的稳定性。实验结果有助于建立模型原子计算数据库，能够预测界面演化和合金形成。通过这种方式，研究提高了预测和设计具有特定结构的合金的能力。这项活动的更广泛影响包括通过指导和实验室研究以及参加国家会议，对研究生和本科生进行物理、计算机科学和工程方面的培训。通过对离子束设施的支持，以及对离子束分析学生的培训，加强了与当地薄膜涂料行业的合作关系，为薄膜行业的职业发展提供了支持。

TECHNICAL: The objective of this research is to investigate the potential for ultrathin, metal interlayers to stabilize the metal-metal interface in thin-film structures. A closely coupled combination of experimental observations and model calculations are used to identify those metals which when deposited in monolayer amounts at the interface make possible stable, epitaxial interfaces in systems that are otherwise characterized by interdiffusion and disorder. The interlayer materials, unlike surfactants, remain at the interface to promote chemical, thermal, and structural stability. The interlayer should be atomically thin, unlike conventional diffusion barriers, to minimize the impact on any electronic properties of the device. Simple model calculations based on quantum approximate techniques (BFS method) are used to guide the choice of interlayer materials, depending on the film-substrate combination under study. Experimental observations are used to expand the database of BFS parameters and thereby refine the model. The extension of the interlayer concept to sputtered thin films, typical of industrial processes, is also investigated. The measurements characterize the degree of ordered growth or interdiffusion at the interface using high-energy ion backscattering and channeling, low energy electron diffraction, low-energy ion scattering, and X-ray photoelectron diffraction. Core-level photoelectron binding energies serve to identify compound formation at the interface. NONTECHNICAL: The intellectual merit of this activity stems from the anticipated advances made in understanding alloy formation at metal-metal interfaces, and in particular the use of metal interlayers for improved stability in thin film devices. Results from the experiments help build a database for model atomistic calculations, capable of predicting interface evolution and alloy formation. In this way the research improves the capability to predict and design alloys with specific structures. Broader impacts of this activity include the training of graduate and undergraduate students in physics, computer science, and engineering, through mentoring and laboratory research and through participation at national meetings. A partnership with local industry for thin film coatings is enhanced through support of the ion beam facility, as well as the training of students in ion beam analysis for careers in the thin film industry.