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Wei-Chang David Yang

Materials Research Engineer

National Institute of Standards and Technology

Biography

David is a Materials Research Engineer within the Physical Measurement Laboratory at the National Institution of Standards and Technology (NIST). His background in Materials Science & Engineering includes a bachelor’s and a master’s degree at the National Tsing Hua University, Taiwan, a Ph.D. at Purdue University, West Lafayette, and postdoctoral training at NIST.

His past research experience, current and proposed work are rooted in understanding light-matter interactions in solid-state materials. For the graduate research, he investigated colloid synthesis of copper-zinc-tin chalcogenide (CZTSSe) nanoparticles to improve CZTSSe thin-films obtained by sintering the nanoparticles. The resultant solar cells showed a world-record power conversion efficiency at the time for CZTSSe made of colloid precursors. His current research interest at NIST is focused on elucidating catalytic mechanisms at the gas-solid interface of plasmonic nanostructures under reactive conditions using environmental scanning transmission electron microscopy (ESTEM) and correlative spectroscopy, including cathodoluminescence and Raman Spectroscopy.

Interests

  • In Situ & Operando Electron Microscopy
  • Nanoplasmonics
  • Heterogeneous Catalysis

Education

  • Ph.D. - Materials Engineering, 2015

    Purdue University

  • M.S. - Materials Science & Engineering, 2006

    National Tsing Hua University (Taiwan)

  • B.S. - Materials Science & Engineering, 2004

    National Tsing Hua University (Taiwan)

Experience

 
 
 
 
 

Materials Research Engineer

National Institute of Standards and Technology (NIST)

Jan 2020 – Present Gaithersburg, Maryland

Develop and disseminate new measurement methods and application areas, utilizing an environmental transmission electron microscope (ETEM) and other optical analytical methods for advanced nanoscale devices, catalysts, and electronic materials.

Two-dimensional layered van der Waals heterostructures

  • Probe momentum forbidden excitons in encapsulated monolayer TMDC using correlative EELS and Cathodoluminescence (CL).

Dynamic process during catalytic reactions

  • Develop catalyst decoking (Ni/SiO2) driven by deep ultraviolet surface plasmons of Al nanostructures.
  • Measure structural fluctuations and phase transformations mediated by surface strains in catalysts under reaction conditions.
 
 
 
 
 

PML-UMD Postdoc Fellow

  • Institute for Research in Electronics and Applied Physics, University of Maryland, College Park.
  • Physical Measurement Laboratory, NIST.

Mar 2015 – Jan 2020 Gaithersburg, Maryland

Plasmon-induced chemical processes at gas-solid interfaces

  • Utilizing electron-beam-excited localized surface plasmon (LSP) resonance to drive chemical reactions at the gas-solid interface.
  • Characterizing LSP resonance and gas adsorption on the catalyst surface using in-situ EELS in an environmental TEM.
  • Synthesizing facet-controlled nanostructures to accommodate selective LSP modes and gas adsorption on metal surface.
  • Simulating LSP resonance energies and electric field using boundary element method (BEM) calculations in MATLAB.
  • Analyzing hyperspectral datasets using unsupervised machine learning algorithms to achieve unbiased data analysis.

In-situ study of carbon nanotube growth and optical spectroscopy in a TEM

  • Investigating carbon nanotube (CNT) growth using metal catalysts, such as Co, Ni and Na, in an environmental TEM.
  • Conducting in-situ Raman spectroscopy and maintaining rigorous safe laboratory practices during carbon nanotube growth.
  • Identifying defect-mediated charge-carrier recombination at grain boundaries in CdTe using cathodoluminescence (CL).
  • Characterizing the electronic structure of transition metal chalcogenide 2D materials using STEM-CL and valence EELS.

Recent Publications

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Low-Temperature Growth of Carbon Nanotubes Catalyzed by Sodium-Based Ingredients

Synthesis of low-dimensional carbon nanomaterials such as carbon nanotubes (CNTs) is a key driver for achieving advances in energy …
Richard Li, Erica F. Antunes, Estelle Kalfon-Cohen, Akira Kudo, Luiz Acauan, Wei-Chang D. Yang, Canhui Wang, Kehang Cui, Andrew H. Liotta, Ananth Govind Rajan, Jules Gardener, David C. Bell, Michael S. Strano, J. Alexander Liddle, Renu Sharma, Brian L. Wardle
PDF DOI

In situ oxidation and reduction of cerium dioxide nanoparticles studied by scanning transmission electron microscopy

Cerium dioxide nanocubes and truncated octahedra were reduced and oxidized in the scanning transmission electron microscope. The …
Aaron C. Johnston-Peck, Wei-Chang D. Yang, Jonathan P. Winterstein, Renu Sharma, Andrew A. Herzing
PDF DOI

In Situ Atomic-Scale Probing of the Reduction Dynamics of Two-Dimensional Fe2O3 Nanostructures

Atomic-scale structural dynamics and phase transformation pathways were probed, in situ, during the hydrogen-induced reduction of Fe2O3 …
PDF DOI

An in situ phosphorus source for the synthesis of Cu3P and the subsequent conversion to Cu3PS4 nanoparticle clusters

The search for alternative earth abundant semiconducting nanocrystals for sustainable energy applications has brought forth the need …
Erik J. Sheets, Wei-Chang Yang, Robert B. Balow, Yunjie Wang, Bryce C. Walker, Eric A. Stach, Rakesh Agrawal
PDF DOI

9.0% efficient Cu2ZnSn(S,Se)4 solar cells from selenized nanoparticle inks

Thin-film solar cells using Cu2ZnSn(S,Se)4 absorber materials continue to attract increasing attention. The synthesis of kesterite …
Caleb K. Miskin, Wei-Chang Yang, Charles J. Hages, Nathaniel J. Carter, Chinmay S. Joglekar, Eric A. Stach, Rakesh Agrawal
PDF DOI
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Popular Topics

Absorption Catalysis Catalyst Chemical vapor deposition Crystal growth CZTS CZTSSe Earth abundant Electrical properties and parameters Field effect transistors Grain Layers Nanocrystals Nanoparticles Nanotubes Raman spectroscopy Scanning transmission electron microscopy Solar cells Thin films Transmission electron microscopy

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