Charles Ahn

About

Charles Ahn is the John C. Malone Professor of Applied Physics and a Professor of Mechanical Engineering and Physics at Yale University. His research group focuses on the fabrication and study of the physical properties of novel complex oxide materials, utilizing advanced growth and characterization techniques such as molecular beam epitaxy and synchrotron x-ray scattering. His current research interests include the physics and technology of multifunctional oxides, nanofabrication, electronic control of complex order parameters in correlated oxides, and the development of nonvolatile logic switches for post-CMOS computing paradigms. Dr. Ahn earned his Ph.D. from Stanford University in 1996 and has received numerous honors, including being a Fellow of the American Physical Society, the AVS Peter Mark Memorial Award, the David and Lucile Packard Fellowship in Science and Engineering, and the Alfred P. Sloan Fellowship. He has held leadership roles such as Director of the Yale SEAS Cleanroom, Director of the Yale Institute for Nanoscience and Quantum Engineering, and Director of the Yale Center for Research on Interface Structures and Phenomena, an NSF MRSEC. His work contributes significantly to the understanding and development of complex oxide materials and their applications in advanced electronic devices.

Research topics

• Computer Science
• Physics
• Materials science
• Condensed matter physics
• Quantum mechanics
• Chemistry
• Crystallography
• Optics
• Optoelectronics
• Nanotechnology

Selected publications

• Designing and controlling the properties of transition metal oxide quantum materials

  Nature Materials · 2021 · 97 citations

  1st authorCorresponding
  DOI

• Stabilization of Competing Ferroelectric Phases of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>HfO</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>under Epitaxial Strain

  Physical Review Letters · 2020 · 95 citations

  Hafnia (HfO_{2})-based thin films have promising applications in nanoscale electronic devices due to their robust ferroelectricity and integration with silicon. Identifying and stabilizing the ferroelectric phases of HfO_{2} have attracted intensive research interest in recent years. In this work, first-principles calculations on (111)-oriented HfO_{2} are used to discover that imposing an in-plane shear strain on the metastable tetragonal phase drives it to a polar phase. This in-plane-shear-in…

  DOI

• Superconducting Nd _{1− <i>x</i>} Eu <i> _x </i> NiO ₂ thin films using in situ synthesis

  Science Advances · 2023-07-05 · 58 citations

  articleOpen accessSenior authorCorresponding

  We report on superconductivity in Nd 1− x Eu x NiO 2 using Eu as a 4f dopant of the parent NdNiO 2 infinite-layer compound. We use an all–in situ molecular beam epitaxy reduction process to achieve the superconducting phase, providing an alternate method to the ex situ CaH 2 reduction process to induce superconductivity in the infinite-layer nickelates. The Nd 1− x Eu x NiO 2 samples exhibit a step-terrace structure on their surfaces, have a T c onset of 21 K at x = 0.25, and have a large upper…

  PublisherOA PDFDOI

• High‐Resolution Crystal Truncation Rod Scattering: Application to Ultrathin Layers and Buried Interfaces

  Advanced Materials Interfaces · 2020 · 42 citations

  Senior authorCorresponding

  Abstract In crystalline materials, the presence of surfaces or interfaces gives rise to crystal truncation rods (CTRs) in their X‐ray diffraction patterns. While structural properties related to the bulk of a crystal are contained in the intensity and position of Bragg peaks in X‐ray diffraction, CTRs carry detailed information about the atomic structure at the interface. Developments in synchrotron X‐ray sources, instrumentation, and analysis procedures have made CTR measurements into extremely…

  DOI

• Solid state reduction of nickelate thin films

  Physical Review Materials · 2023-01-31 · 31 citations

  articleOpen accessSenior author

  The square-planar nickelates are a class of superconductors analogous to the cuprates and promise to provide insight into the pairing mechanism in high-temperature superconducting oxides. The parent phase of doped superconducting films is ${\mathrm{NdNiO}}_{2}$, which is prepared by reducing ${3}^{+}$ Ni in ${\mathrm{NdNiO}}_{3}$ films. In this paper, we develop an ultrahigh vacuum reduction method using aluminum deposited on top of the ${3}^{+}$ nickelates and monitor the reduction process in r…

  PublisherOA PDFDOI

Recent grants

• Electronic Properties of Oxide-Semiconductor Interfaces

  NSF · $226k · 2007–2010

• Coupling Multifunctional Oxides to Semiconductors

  NSF · $660k · 2013–2018

• Center for Innovative Structures and Phenomena

  NSF · $13.6M · 2011–2018

Frequent coauthors

• F. J. Walker

  Yale University

  412 shared

• Sohrab Ismail‐Beigi

  Yale University

  165 shared

• Ke Zou

  University of British Columbia

  83 shared

• Divine P. Kumah

  79 shared

• C. A. F. Vaz

  Paul Scherrer Institute

  77 shared

• Ankit Disa

  Cornell University

  71 shared

• Eric I. Altman

  Yale University

  57 shared

• Y. Segal

  Massachusetts Institute of Technology

  56 shared

Awards & honors

• Fellow of the American Physical Society
• AVS Peter Mark Memorial Award
• David and Lucile Packard Fellowship in Science and Engineeri…
• Alfred P. Sloan Fellowship

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