CSL PhD student Zichao Ye receives Materials Research Society Graduate Student Silver Award

Zichao Ye, CSL and materials science and engineering PhD student advised by CSL and MatSE Professor Les Allen, has received the Materials Research Society (MRS) Graduate Student Silver Award for his work presented at the 2017 MRS Spring Meeting held at Phoenix, AZ during April 17-21, 2017.

The national award recognizes graduate students with exceptional research in materials science. Ye received a silver award for his contribution on “Critical Size for Bulk-to-Discrete Transition: Emergent Size Effect Observed in Aliphatic Layers.”

When a material shrinks in size, the melting properties of that material normally adjust in tandem. However, Ye’s work found an abrupt and irregular phenomenon in 2D aliphatic layers—a large category of materials that are found in electronics, sensors, polymeric products, and biology.

This phenomenon challenges the traditional thinking of size-dependent melting and is critical to predict how these materials behave in electronics and biophysics applications.

Using advanced measurement and imaging techniques, including nanocalorimetry (invented within the group), nuclear magnetic resonance, and electron diffraction, Ye and Allen found that after being reduced to a certain critical dimension, the material property fundamentally and abruptly altered as if it were a new material.

“Even though the composition and crystal structure of the material, silver alkanethiolate, scales linearly as expected, when its size decreases below a critical point, the property changes so dramatically that you can say it’s a different material compared to its counterparts with larger sizes,” said Ye, who received his PhD in materials science and engineering in March 2017.

Ye observed that the thermodynamic property and chemical environment of a variety of aliphatic layers present significant changes as their size reduces. This discovery is important for understanding the melting of small layered materials. When the size of silver alkanethiolate, a type of aliphatic material, reaches the critical dimension, its melting point is altered by about 100 degrees. This has applications in electronics and biophysics.

“If we understand how the size of an electronic material affects the melting points, we can manipulate electronics so they can operate under higher temperatures,” said Ye.

Biological molecules found in cell membranes also have similar structures to aliphatic layers. The thermodynamic properties of these structures are of particular interest for developing robust membrane-expanding drugs, which can be used as an anesthetic.

“Zichao was the first one to establish a firm experimental link between two of the measurement techniques used: nanocalorimetry, which averages information from all molecules, and nuclear magnetic resonance, which measures individual molecules,” said Allen, a professor of materials science and engineering. “This combination of measurements made understanding the melting physics of these materials possible.”

Ye collaborated with Lito de la Rama, Mikhail Efremov, Andrew Sutrisno, professors Les Allen (MatSE PhD advisor), Jian-Min Zuo (MatSE), Waltraud Kriven (MatSE), Paul Braun, (MatSE) and Joe Lyding (ECE, CSL). This research is supported by NSF-DMR-SSMC. After graduating, Ye started a new job at Lam Research Corporation, a company that builds semiconductor processing equipment used in the nanofabrication of integrated circuits.