Enhanced Growth in Atomic Layer Deposition of Transition Metals: The Role of Surface Diffusion and Nucleation Sites

Next BIU Engineering Colloquium,
Dr. Amnon Rothman, Tuesday, 26.12.23 @13:00

BIU Engineering  Building 1103,  Room 329

(Zoom link will be sent on Monday)

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We are delighted to host

Dr. Amnon Rothman

Stanford University

Dr. Rothman will give a talk on the subject:

Enhanced Growth in Atomic Layer Deposition of Transition Metals: The Role of Surface Diffusion and Nucleation Sites

Abstract: Noble metal thin films have attracted significant interest owing to their distinctive properties and structures, which make them ideal for applications in microelectronics, catalysis, energy, and photovoltaics. While several parameters influence the properties of these metals for such applications, the deposition process remains a critical factor. Atomic Layer Deposition (ALD) stands out as a prevalent deposition technique due to its surface-sensitive nature. The ALD process is characterized by its self-limiting surface reactions, promoting a layer-by-layer growth mechanism and allowing for precise control over film thickness and conformality. However, challenges arise in achieving continuous, pinhole-free noble metal ALD layers on oxide surfaces, often resulting in low film quality. These challenges can be traced back to the lack of adequate nucleation sites and the poor wettability of the low-surface energy substrates. The research studied the impact of substrate surface functionalization using organometallic molecules, such as trimethylaluminum (TMA) and diethylzinc (DEZ), on the nucleation and growth of Ru layers. The results reveal an enhancement in both nucleation density and the average diameter of the Ru nanoparticles deposited, and these improvements were attributed to an increase in both nucleation sites and elevated surface diffusivity. The latter effect is speculated to result from a reduction in the substrate's surface free energy. The study also examines the influence of substrate surface characteristics, including surface termination and crystallinity, on the nucleation and growth of Ru metal via ALD. The morphologies of the resulting Ru thin films are studied using scanning electron microscopy (SEM), atomic force microscopy (AFM), and grazing incidence small angle x-ray scattering (GISAXS). These analytical results are integrated with an experimental model to elucidate the differences in growth mechanisms observed across substrates. The findings underscore the importance of substrate choice in the ALD process and broaden our understanding of Ru metal growth. This research serves as an important step in optimizing the ALD process for various applications by tailoring substrate selection.

Short bio: Dr. Amnon Rothman is a distinguished materials scientist and chemist with a wide educational background and a rich history of research experience. Currently serving as a Postdoctoral Fellow at Stanford University, Dr. Rothman specializes in the nucleation and growth mechanisms of nanomaterials and thin films. With a Ph.D. in Chemistry from the Weizmann Institute of Science and a master's in Materials Science from Ben-Gurion University of the Negev, his academic journey has been marked by a consistent pursuit of innovation and excellence. At Stanford, under the guidance of Prof. Stacey F. Bent, he has been working on noble metal ALD on low surface energy substrates, aiming to gain an atomistic understanding of ALD nucleation and growth. His expertise includes a multitude of surface and electron microscopy techniques, which he has honed over the years through extensive research and application. Dr. Rothman’s professional experience extends beyond academia, having led a materials and failure analysis group at Motorola Solutions in Israel. His work has earned him several prestigious awards, including the Ben-Gurion University Dean's Award, reflecting the significance and impact of his research. An active contributor to the scientific community, Dr. Rothman has several high-impact publications and is a member of multiple professional associations. He is also dedicated to education and mentorship, teaching at Stanford University and the Weizmann Institute of Science and guiding the next generation of scientists.