Professor

Research Interests:

Real-Time X-ray Studies of Materials Processes

Our research investigates how materials evolve on atomic and nano- length scales during growth, patterning or electrochemical function using real-time x-ray techniques. Many of the experiments use the high brightness of synchrotron x-ray sources – the National Synchrotron Light Source (NSLS-II) at Brookhaven National Laboratory on Long Island and the Advanced Photon Source (APS) at Argonne National Laboratory outside of Chicago.  We have been particularly active in pushing forward the application of the coherent x-ray scattering technique of X-ray Photon Correlation Spectroscopy (XPCS). Where possible, our research makes contact with fundamental theory and simulation. In the last few years, our detailed interest has been in three directions – understanding surface and thin film processes, studying the relationship between atomic structure and function in solid oxide fuel cell cathodes, and examining the structure of molten salts of interest for energy applications.

Research Group Website: Materials X-Ray Diffraction Lab | Boston University (bu.edu)

Recent Publications:

  1. “Interplay of broken symmetry and delocalized excitations in the insulating state of 1T-TaS2”, Xun Jia1, Anubhab Haldar, Jungho Kim, Yilin Wang, Gilberto Fabbris, Karl Ludwig, Stefanos Kourtis, Mary Upton, Yu Liu, Wenjian Lu, Xuan Luo, Yu-Ping Sun, Diego Casa, Sahar Sharifzadeh, Pierre T. Darance, Yue Cao, arXiv: 2210.01181 (2023), Phys. Rev. B, in press.
  2. “X-ray and Molecular Dynamics Study of the Temperature-Dependent Structure of FLiNaK”, Jicheng Guo, Yifan Zhang, Karl Ludwig, Haoxuan Yan, Alexander Levy, Anubhav, Wadehra, Michael Gao, Chris Benmore, Melissa Rose, Nicholas Condon, Adam Powell, Yu Zhong and Uday Pal (* contributing equally). Nucl. Mater. Energy 37, 101530 (2023).
  3. “Local Step-Flow Dynamics in Thin Film Growth with Desorption”, Xiaozhi Zhang, Jeffrey G. Ulbrandt, Peco Myint, Andrei Fluerasu, Lutz Wiegart, Yugang Zhang, Christie Nelson, Karl F. Ludwig and Randall L. Headrick, Phys. Rev. Mater., in press. arXiv:2305.18661.
  4. “Influence of plasma species on the early-stage growth kinetics of epitaxial InN grown by plasma-enhanced atomic layer deposition”, Jeffrey Woodward, Samantha Rosenberg, David Boris, Michael Johnson, Scott Walton, Scooter Johnson, Zachary Robinson, Neeraj Nepal, Karl F. Ludwig, Jr., Jennifer Hite, and Charles (Chip) Eddy Jr., J. of Vac. Sci. Technol. A 40, 062405 (2022). Chosen as an Editor’s Pick.
  5. “Early Stage Growth of Amorphous Thin Film: Average Kinetics, Nanoscale Dynamics and Pressure Dependence”, Chenyu Wang, Karl F. Ludwig, Christa Wagenbach, Meliha G. Rainville, Suresh Narayanan, Hua Zhou, Jeffrey G. Ulbrandt, Randall L. Headrick, arXiv: 2111.14285 (2021), Phys. Rev. Mater. 6, 045601 (2022).
  6. “In Situ GISAXS Observation of Ion-Induced Nanoscale Pattern Formation on Crystalline Ge(001) in the Reverse Epitaxy Regime”, Denise Erb, Peco Myint, Kenneth Evans-Lutterodt, Karl Ludwig and Stefan Facsko, Phys. Rev. B 104, 235434 (2021).
  7. “Nanoscale dynamics during self-organized ion beam patterning of Si: II. Kr+Bombardment”, Peco Myint, Karl F. Ludwig, Jr., Lutz Wiegart, Yugang Zhang, Andrei Fluerasu, Xiaozhi Zhang, Randall L. Headrick, arXiv: 2007.12294 (2020), Phys. Rev. B 103, 195424 (2021).
  8. “Nanoscale dynamics during self-organized ion beam patterning of Si: I. Ar+Bombardment”, Peco Myint, Karl F. Ludwig, Jr., Lutz Wiegart, Yugang Zhang, Andrei Fluerasu, Xiaozhi Zhang, Randall L. Headrick, arXiv: 2007.12253 (2020), Phys. Rev. B 103, 195423 (2021).
  9. “de Gennes Narrowing and the Relationship Between Structure and Dynamics in Self-Organized Ion Beam Nanopatterning”, Peco Myint, Karl F. Ludwig, Jr., Lutz Wiegart, Yugang Zhang, Andrei Fluerasu, Xiaozhi Zhang, Randall L. Headrick, arXiv: 2007.07395 (2020), Phys. Rev. Lett. 126, 016101 (2021).
  10. “Probing Subcellular Nanostructure of Engineered Human Cardiomyocytes in 3D Tissue”, Josh Javor, Jourdan Ewoldt, Paige Cloonan, Anant Chopra, Rebeccah Luu, Guillaume Freychet, Mikhail Zhernenkov, Karl Ludwig, Jonathan Seidman, Christine Seidman, Christopher Chen, David Bishop, Nature MicroNano 7, 10 (2021).
  11. “Measurement of Ehrlich-Schwoebel barrier conntribution to the self-organized formation of ordered surface patterns on Ge(001)”, Peco Myint, Denise Erb, Xiaozhi Zhang, Lutz Wiegart, Yugang Zhang, Andrei Fluerasu, Randall Headrick, Stefan Facsko and Karl F. Ludwig, Jr., arXiv: 2008.06504, Phys. Rev. B 102, 201404(R) (2020).
  12. “Coherent X-rays Measurement of Step-Flow Propagation During Growth on Polycrystalline Thin Film Surfaces”, R.L. Headrick, J.G. Ulbrandt, P. Myint, J. Wan, Y. Li, A. Fluerasu, Y. Zhang, L. Wiegert and K.F. Ludwig, Jr., Nature Communications 10, 2638 (2019).
  13. “Nanoscale Kinetics and Dynamics During Ar+ Patterning of SiO2”, M. Mokhtarzadeh, J.G. Ulbrandt, P. Myint, S. Narayanan, R.L. Headrick and K.F. Ludwig, Jr., Phys. Rev. B 99, 165429 (2019).
  14. “Influence of Temperature on Atomic Layer Epitaxial Growth of Indium Nitride Assessed with In Situ Grazing Incidence Small-Angle X-ray Scattering”, J.M. Woodward, S.G. Rosenberg, A.C. Kozen, N. Nepal, S.D. Johnson, C. Wagenbach, A.H. Rowley, Z.R. Robinson, H. Joress, K.F. Ludwig, Jr. and C.R. Eddy, Jr., J. of Vac. Sci. Technol. A 37, 030901 (2019). Chosen as an Editor’s Pick.
  15. “In-situ Studies of Low Temperature Atomic Level Processing of GaN Surfaces for Atomic Layer Epitaxial Growth”, S.G. Rosenberg, C. Wagenbach, V.R. Anderson, S.D. Johnson, N. Nepal, A.C. Kozen, J. Woodward, Z. Robinson, M. Munger, H. Joress, K.F. Ludwig and C.R. Eddy, Jr., J. of Vac. Sci. Technol. A 37, 020928 (2019).
  16. “Low Temperature Surface Preparation of GaN Substrates for Atomic Layer Epitaxial Growth: Assessment of Ex Situ Preparations”, S.G. Rosenberg, D.J. Pennachio, C. Wagenbach, S.D. Johnson, N. Nepal, A.C. Kozen, J. Woodward, Z. Robinson, H. Joress, K.F. Ludwig, C.J. Palmstrom, C.R. Eddy, Jr., J. of Vac. Sci. Technol. A 37, 020908 (2019).
  17. “Understanding the Effect of Nitrogen Plasma Exposure on Plasma Assisted Atomic Layer Epitaxy of InN Monitored by Real Time Grazing-Incidence Small-Angle X-ray Scattering”, N. Nepal, V.R. Anderson, S.D. Johnson, B.P. Dowoney, D.J. Meyer, Z.R. Robinson, J.M. Woodward, K.F. Ludwig, Jr. and C.R. Eddy, Jr., J. of Vac. Sci. Technol. A 37, 020910 (2019). Chosen as an Editor’s Pick.
  18. “Measurement of Bulk Oxygen Diffusivity in (La0.8S0.2)0.95MnO3±d”, J. Davis, U. Pal, S. Gopalan, K. Ludwig and S. Basu, JOM 71, 96 (2019).
  19. “Sawtooth Structure Formation Under Nonlinear-Regime Ion Bombardment”, J. Perkinson, J. Swenson, A. DeMasi, C. Wagenbach, K. Ludwig, S. Norris and M. Aziz, J. Phys.: Condens. Matter 30, 294004 (2018).
  20. “Simulations of Co-GISAXS During Kinetic Roughening of Growth Surfaces”, Mahsa Mokhtarzadeh and Karl Ludwig, J. Synchrotron Rad.24, 1187 (2017).
  21. “Analysis of InGaN Nanodots Grown by Droplet Heteroepitaxy Using Grazing Incidence Small-Angle X-ray Scattering and Electron Microscopy”, J.M. Woodward, A. Yu. Nikiforov, K.F. Ludwig, Jr., and T.D. Moustakas, J. Appl. Phys. 122, 065305 (2017).
  22. “Surface Segregation in Lanthanum Strontium Manganite Thin Films and its Potential Effect on the Oxygen Reduction Reaction”, J.N. Davis, K.F. Ludwig, K.E. Smith, J.C. Woicik, S. Gopalan, U.B. Pal and S.N. Basu, J. Electrochem. Soc. 164, F3091 (2017).
  23. “Distinguishing Physical Mechanisms Using GISAXS Experiments and Linear Theory: The Importance of High Wavenumbers”, S. Norris, J. Perkinson, M. Mokhtarzadeh, E. Anzenberg, M. Aziz and K. Ludwig, Scientific Reports 7, 2016 (2017).
  24. “Characterization of the LCLS ‘Nanosecond Two-Bunch’ Mode for X-ray Speckle Visibility Spectroscopy Experiments”, Y. Sun, D. Zhu, S. Song, F.-J. Decker, M. Sutton, K. Ludwig, W. Roseker, G. Grübel, S. Hruszkewycz, G.B. Stephenson, P.H. Fuoss and A. Robert, Proc. SPIE 10237N, doi.10.1117/12.2265454 (2017).
  25. “Plasma-Assisted Atomic Layer Epitaxial Growth of Aluminum Nitride Studied with Real Time Grazing Incidence Small Angle X-ray Scattering”, V.R. Anderson, N. Nepal, S.D. Johnson, Z.R. Robinson, A. Nath, A.C. Kozen, S.B. Qadri, A. DeMasi, J.K. Hite, K.F. Ludwig and C.R. Eddy, Jr., J. Vac. Sci. Technol. A 35, 031508 (2017).
  26. “Real-time Growth Study of Plasma Assisted Atomic Layer Epitaxy of InN Films by Synchrotron X-ray Methods”, N. Nepal, V.R. Anderson, S.D. Johnson, B.P. Downey, D.J. Meyer, A. DeMasi, Z.R. Robinson, K.F. Ludwig and C.R. Eddy, Jr., J. Vac. Sci. Technol. A 35, 031504 (2017).
  27. “A Case Study of ALD Encapsulation of Quantum Dots: Embedding Supported CdSe/CdS/ZnS Quantum Dots in a ZnO Matrix”, K. Devloo-Casier, P. Geiregat, K. Ludwig, K. Van Stiphout, A. Vantomme, Z. Hens, C. Detavernier, J. Dendooven, J. Phys. Chem. C 120, 18039 (2016).
  28. “Chemical Characterization of Surface Precipitates in La0.7Sr0.3 xCo0.2Fe0.8O3-δ as Cathode Material for Solid Oxide Fuel Cells”, Y. Yu, A. Nikiforov, T. Kasper, J. Woicik, K.F. Ludwig, S. Gopalan, U. Pal and S. Basu, Journal of Power Sources 333, 247 (2016).
  29. “Effect of Sr Content and Strain on Sr Surface Segregation of La1-xSrxCo0.2Fe0.8O3-δ as Cathode Material for Solid Oxide Fuel Cells, Y. Yu, K.F. Ludwig, J.C. Woicik, S. Gopalan, U. Pal, T.C. Kaspar and S.N. Basu, ACS Applied Materials and Interfaces 8, 26704 (2016).
  30. “Using Coherent X-rays to Directly Measure the PropagationVelocity of Defects During Thin Film Deposition”, Jeffrey G. Ulbrandt, Meliha G. Rainville, Christa Hoskin, Suresh Narayanan, Alec R. Sandy, Hua Zhou, Karl F. Ludwig, Jr. and Randall L. Headrick, Nature Physics 12, 794 (2016).

For a full list of publications, please see the attached CV.

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