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A research team at UNIST has developed a new deposition technology that enables the uniform mixing of different metals within a single atomic layer. This advancement holds significant promise for applications across semiconductor manufacturing, electrochemical catalysis, and various other fields.

Led by Professor Soo-Hyun Kim from the Department of Materials Science and Engineering and the Graduate School of Semiconductor Materials and Devices Engineering at UNIST, the team successfully fabricated alloy thin films using an improved atomic layer deposition (ALD) method, termed atomic layer modulation (ALM). This innovative approach allows for precise atomic-level blending of precious metals such as platinum (Pt) and ruthenium (Ru), overcoming longstanding limitations of conventional methods.

The research was led by Yeseul Son, a graduate student enrolled in a combined Master's and Doctoral program at the Graduate School of Semiconductor Materials and Devices Engineering at UNIST, serving as the first author. The findings were online in Advanced Science on May 28, 2025.

Traditional ALD involves sequentially depositing individual atomic layers, which achieves highly controlled film thicknesses. However, creating alloys with multiple metals typically requires alternating layers, often resulting in uneven compositions and the formation of distinct metal boundaries.

The new ALM technique addresses these challenges by simultaneously injecting precursor gases for both metals within a single reaction cycle. This process induces atomic-level mixing during deposition, producing homogeneous alloy films with a controlled composition ratio of Pt to Ru—from 97:3 to 28:72—and uniform elemental distribution throughout the entire film.

This innovative process has significant implications for semiconductor manufacturing, especially in fabricating complex 3D structures such as transistors and interconnects, where uniform thin films are critical. The team successfully deposited alloy coatings on structures with an aspect ratio of 30:1, achieving 100% step coverage—meaning the film uniformly coated both the outer surfaces and deep inside narrow trenches with nearly identical thickness.

Functional testing confirmed the excellent catalytic performance of these alloys, demonstrating high activity in water-splitting reactions and efficient production of hydrogen and oxygen. Such results underscore their potential as effective catalysts for electrochemical applications.

The success of this alloy synthesis stems from meticulous control of reaction parameters—including temperature and precursor injection sequences—to mitigate steric hindrance, which can impede surface reactions involving bulky molecules.

Professor Kim said, "This represents a breakthrough in overcoming the longstanding challenge of fabricating uniform alloy films via ALD. The ability to precisely mix different metals at the atomic level opens new avenues for designing advanced functional materials." He further added, "Because the principles underlying this technology can be extended to various metal combinations beyond precious metals, it holds great promise for widespread applications in catalysts, semiconductors, sensors, and beyond."