Film Growth Dynamics During Pulsed Sputter Deposition

Yinming Wang | 17-ERD-048


Novel materials synthesis and development using physical vapor deposition require our fundamental understanding of plasma conditions and film growth dynamics. A central theme is to control materials microstructure. Over the last few decades, the difficulty of thick heavy metal coatings has been one of the major bottlenecks limiting our studies of the important family of inertial confinement fusion (ICF) designs with colliding shell targets. Our previous attempts to fabricate such coatings by conventional direct current magnetron sputtering has had limited success due to the inherent complexity and our limited understanding of the deposition process.

In this project, we investigated the physics of a novel and promising pulsed sputter deposition process. We expanded the scientific foundation of sputter deposition processes through a combination of well-posed experiments and state-of-the-art characterizations. The following important, scientific milestones were achieved: 1) successfully installed and tested a high-power impulse magnetron sputtering (HiPIMS) system; 2) deployed a novel set of in situ diagnostics during pulsed deposition, including a multibeam optical stress sensor system for real-time stress measurements and a Langmuir probe for measuring the physical properties of plasmas, which allowed us to dynamically monitor plasma conditions, ion flux and energy distributions, and film stress; 3) investigated and obtained a fundamental understanding of HiPIMS on microstructure and stress control; 4) successfully synthesized and demonstrated nanocrystalline-nanotwinned metals that possess record-breaking strength; and 5) successfully obtained high-quality, leak-proof Cr metal shells via HiPIMS method. The outcomes of this project could have transformational scientific and programmatic impacts, enabling novel materials synthesis and an experimental campaign with colliding shell target designs. The basic understanding of the deposition process has important implications to a broad range of industrial applications.

Impact on Mission

This project expanded LLNL's core competencies in the field of advanced materials and manufacturing to build necessary knowledge for the fabrication of novel materials with unprecedented mechanical and physical properties. Our synthetic approach and novel materials could have broad, long-term impacts in the materials science community. This project also helps to accelerate the fabrication of next-generation metal shells poised to have long-lasting impacts on stockpile stewardship science and ICF science and technology.

Publications, Presentations, Etc.

Engwall, A., et al. 2018. "Beneficial Properties of HiPIMS W Thin Films and the Effect of Standard Processing Parameters." Surface and Coatings Technology . LLNL-JRNL-759980.

––– . 2018. "High Power Impulse Magnetron Sputtering of W Thin Films." American Academy of Crystal Growth and Epitaxy (AACGE) Western Section Conference on Crystal Growth and Epitaxy, South Lake Tahoe CA, June 2018. LLNL-POST-752586.

––– . 2019. "Metal Shell Fabrication with High Power Impulse Magnetron Sputtering." Target Fabrication Meeting, Annapolis MD, April 2019. LLNL-PRES-772020.

––– . 2019. "High Power Impulse Magnetron Sputtering." 46th International Conference on Metallurgical Coatings and Thin Films (ICMCTF), San Diego CA, May 2019. LLNL-PRES-774774.

––– . 2019. "Enhanced Properties of Tungsten Films by High-Power Impulse Magnetron Sputtering." Surface and Coatings Technology 363: 191—197. doi: 10.1016/j.surfcoat.2019.02.055. LLNL-JRNL-759980.

––– . 2019. "High Power Impulse Magnetron Sputtering of Tungsten Thin Films." 12th Annual LLNL Postdoc Poster Symposium, Livermore CA. LLNL-POST-772613.

Ke, X., et al. 2019. "Ideal Maximum Strengths and Defect-Induced Softening in Nanocrystalline-Nanotwinned Metals." Nature Materials . doi: 10.1038/s41563-019-0484-3. LLNL-JRNL-680480.

Ping, Y., et al. 2018. "Enhanced Energy Coupling for Indirectly Driven Inertial Confinement Fusion." Nature Physics . doi:10.1038/s41567-018-0331-5. LLNL-JRNL-745363.

Wang, Y., et al. 2017. "Implementation of HiPIMS for Metal Shell Fabrications." Target Fabrication Conference, Las Vegas, NV, March 2017. LLNL-PRES-725625.

Yuan, B. et al. 2019. "Enhanced Energy Coupling for Indirectly Driven Inertial Confinement Fusion." Nature Physics 15, 138—141. doi: 10.1038/s41567-018-0331-5. LLNL-JRNL-745363.