Karl Ludwig

Karl Ludwig

Office: SCI, Room 217. 617-353-9346
Lab: SCI, Room B46. 617-353-7291
Email:

Office Hours: Fridays 10-11:30 in PRB 459

 

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, the Advanced Photon Source (APS) at Argonne National Laboratory outside of Chicago, the Cornell High-Energy Synchrotron Source (CHESS) at Cornell, and the Linac Coherent Light Source (LCLS) at SLAC.  Where possible, our research makes contact with fundamental theory and simulation.

In the last few years, our detailed interest has been in two directions – understanding surface and thin film processes and studying the relationship between atomic structure and function in solid oxide fuel cell cathodes. Many of our in-situ studies utilize a unique ultra-high vacuum growth and surface modification facility that we have helped develop at the NSLS-II. We have been using it to examine surface morphology evolution during ion bombardment (which can cause the spontaneous growth of surface nanostructures) and issues related to the growth of wide-bandgap group III-V semiconductor films using atomic layer epitaxy (in collaboration with the Eddy group at the Naval Research Laboratory).

Increasingly our experiments utilize coherent x-ray scattering, which provides the ability to probe nanoscale dynamics during growth and patterening. Partially coherent x-ray beams are created using small (few microns) slits in conjunction with a high-brilliance 3rd generation synchrotron source. The disorder on the surface produces speckle patterns in the scattered x-ray intensity. The evolution of the speckle pattern can then be related to the underlying dynamics of structural changes.  The LCLS is the world's first hard x-ray laser and offers unique new opportunies for coherent scattering on femtosecond time scales that we are now exploring.

A second major direction of our work is in solid oxide fuel cells, which offer the potential for highly efficient energy conversion. However improvements in cathode function are needed before their potential can be fully realized. In collaboration with Profs. Pal, Basu and Gopalan in Engineering and Prof. Smith in Physics, we are examining in-situ the near-surface atomic structure of cathode materials in order to better understand the relationship between function and structure.

Recent Publications:

  1. “Simulations of Co-GISAXS During Kinetic Roughening of Growth Surfaces”, Mahsa Mokhtarzadeh and Karl Ludwig, Journal of Synchrotron Radiation, in press.

  2. “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).

  3. “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, Journal of the Electrochemical Society, in press.

  4. “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).

  5. “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 10237, doi.10.1117/12.2265454 (2017).

  6. “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).

  7. “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).

  8. “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).

  9. “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).

  10. “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).

  11. “Using Coherent X-rays to Directly Measure the Propagation Velocity 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).

  12. “Co-GISAXS as a New Technique to Investigate Surface Growth Dynamics”, M.G. Rainville, C. Hoskin, J.G. Ulbrandt, S. Narayanan, A.R. Sandy, H. Zhou, R.L. Headrick and K.F. Ludwig, Jr., Phys. Rev. B 92, 214102 (2015).

  13. “Vacancy Assisted SrO Formation on La0.8Sr0.2Co0.2 Fe0.8O3- Surfaces – A Synchrotron Photoemission Study”, J. Kuyyalil, D. Newby, Jr., J. Laverock, Y. Yu, D. Cetin, S. Basu, K. Ludwig and K.E. Smith, Surf. Sci. 642, 33 (2015).

  14. “Surface Evolution of Lanthanum Strontium Cobalt Ferrite Thin Films at Low Temperatures”, D. Newby Jr., J. Kuyyalil, J. Laverock, K.F. Ludwig, Y. Yu, J. Davis, S. Gopalan, U. Pal, S. Basu and K.E. Smith, Thin Solid Films 589, 655 (2015).

  15. “Ion beam nanopatterning of III-V semiconductors: consistency of experimental and simulation trends within a chemistry-driven theory”, O. El-Atwani, S. Norris, K. Ludwig, S. Gonderman and J.P. Allain, Scientific Reports 5, 18207 (2015).

  16. “Real-Time X-ray Studies of Indium Island Growth Kinetics”, A. DeMasi, M. Rainville and K.F. Ludwig, J. Vac. Sci. and Technol. A 33, 021406 (2015).

  17. “Atomic Layer Deposition-Based Tuning of the Pore Size in MesoPorous Thin Films Studied by In Situ Grazing Incidence Small Angle X-ray Scattering”, J. Dendooven, K. Devloo-Casier, M. Ide, K. Grandfield, M. Kurttepeli, K.F. Ludwig, S. Bals, P. Van Der Voort and C. Detavernier, Nanoscale 6, 14991 (2014).

  18. “Predicting Oxygen Vacancy Non-Stoichiometric Concentration in Perovskites from First Principles”, Heng Luo, Yongwoo Shin, Yang Yu, Deniz Cetin, Karl Ludwig, Uday Pal, Soumendra N. Basu, Srikanth Gopalan, Xi Lin, Appl. Surf. Sci. 323, 65 (2014).

  19. “Model-Independent Test of the Crater Function Theory of Surface Morphology Evolution during Ion Bombardment”, E. Anzenberg, J. Perkinson, M. Aziz and K. Ludwig, Phys. Rev. B 89, 115433 (2014).

  20. “Effect of Atmospheric CO2 on Surface Segregation and Phase Formation in La0.6Sr0.4Co0.2Fe0.8O3- Thin Films”, Yang Yu, Heng Luo, Deniz Cetin, Xi Lin, Karl Ludwig, Uday Pal, Srikanth Gopalan, Soumendra Basu, Appl. Surf. Sci. 323, 71 (2014).

  21. “Effect of Carbon Dioxide on the Cathodic Performance of Solid Oxide Fuel Cells”, Y. Yu, H. Luo, D. Cetin, X. Lin, K. Ludwig, S. Basu, U. Pal, S. Gopalan, ECS Trans. 61, 131 (2014).

  22. “In-Situ Synchrotron Based X-ray Techniques as Monitoring Tools for Atomic Layer Deposition – A Review”, K. Devloo-Casier, K.F. Ludwig, C. Detavernier and J. Dendooven, J. Vac. Sci Technol. A 32, 010801 (2014).

Education:

Ph.D. in Applied Physics: Stanford University - 1986

M.S. in Applied Physics: Stanford University - 1982

B.A. magna cum laude in Physics "With Distinction in All Subjects": Cornell University - 1980

 

Research Descriptions:

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, the Advanced Photon Source (APS) at Argonne National Laboratory outside of Chicago, the Cornell High-Energy Synchrotron Source (CHESS) at Cornell, and the Linac Coherent Light Source (LCLS) at SLAC.  Where possible, our research makes contact with fundamental theory and simulation.

In the last few years, our detailed interest has been in two directions – understanding surface and thin film processes and studying the relationship between atomic structure and function in solid oxide fuel cell cathodes. Many of our in-situ studies utilize a unique ultra-high vacuum growth and surface modification facility that we have helped develop at the NSLS-II. We have been using it to examine surface morphology evolution during ion bombardment (which can cause the spontaneous growth of surface nanostructures) and issues related to the growth of wide-bandgap group III-V semiconductor films using atomic layer epitaxy (in collaboration with the Eddy group at the Naval Research Laboratory).

Increasingly our experiments utilize coherent x-ray scattering, which provides the ability to probe nanoscale dynamics during growth and patterening. Partially coherent x-ray beams are created using small (few microns) slits in conjunction with a high-brilliance 3rd generation synchrotron source. The disorder on the surface produces speckle patterns in the scattered x-ray intensity. The evolution of the speckle pattern can then be related to the underlying dynamics of structural changes.  The LCLS is the world's first hard x-ray laser and offers unique new opportunies for coherent scattering on femtosecond time scales that we are now exploring.

A second major direction of our work is in solid oxide fuel cells, which offer the potential for highly efficient energy conversion. However improvements in cathode function are needed before their potential can be fully realized. In collaboration with Profs. Pal, Basu and Gopalan in Engineering and Prof. Smith in Physics, we are examining in-situ the near-surface atomic structure of cathode materials in order to better understand the relationship between function and structure.