Voyles Group
Science and Technology at the Atomic Scale

Andrew Yankovich

Biography

Andy was born in Saint Paul Minnesota. He received a dual B.A. in physics and mathematics from Saint John’s University in Collegeville MN in 2005. In 2008, he also received a B.S. in materials science & engineering from the University of Minnesota – Twin Cities Campus. Andy received a M.S. in materials science from the University of Wisconsin – Madison in 2011, and is currently continuing towards his Ph.D. as a student and research assistant in Paul Voyle’s research group.

Research Interests

  • Use of atomic resolution TEM, Cs-corrected STEM, energy dispersive spectroscopy (EDS), position averaged convergent beam electron diffraction (PACBED), and frozen phonon multislice simulations to understand the structure of various materials systems to help solve technologically relevant questions.
  • Defect structures responsible for (and limiting) the performance of ZnO, GaN, and InGaN based optoelectronic devices.
  • The doping asymmetry problem of ZnO and making ZnO p-type.
  • Development and use of high precision STEM techniques to measure picometer-scale surface atom contraction in Pt and Au catalysis nanoparticles.
  • Dynamic scattering limits to precision in ABF and HAADF STEM.
  • Standardless atom counting in HAADF STEM images.
  • Utilizing Quantitative STEM to detect single point defects.
  • Advanced data processing methods for atomic-resolution energy dispersive spectroscopy spectrum images.

Publications

  • A. B. Yankovich, B. Berkels, W. Dahmen, P. Binev, and P. M. Voyles, “High-precision scanning transmission electron microscopy at course pixel sampling for reduced electron dose”, Advanced Structural and Chemical Imaging, accepted (2015).
  • A. B. Yankovich, B. Berkels, W. Dahmen, P. Binev, S. I. Sanchez, S. A. Bradley, A. Li, I. Szlufarska, and P. M. Voyles, “Picometer-Precision Analysis of Scanning Transmission Electron Microscopy Images of Platinum Nanocatalysts”, Nature Communications, 5:4155 (2014).
  • A. B. Yankovich, A. V. Kvit, X. Li, F. Zhang, V. Avrutin, H. Liu, N. Izyumskaya, Ü. Özgür, B. Van Leer, H. Morkoç, and P. M. Voyles, “Thickness variations and absence of lateral compositional fluctuations in aberration-corrected STEM images of InGaN LED active regions at low dose”, Microscopy and Microanalysis, 20, 3, 864-868 (2014).
  • A. B. Yankovich and P. M. Voyles, “Precision Limits to STEM Imaging from Dynamical Scattering and Channeling of Sub-Angstrom Electron Probes”, Microscopy and Microanalysis, 20 (S3), page 120-121 (2014).
  • A. B. Yankovich, B. Berkels, W. Dahmen, R. Sharpley, P. Binev, and P. M. Voyles, “Measuring Surface Atom Bond Length Contraction in Au and Pt Nanoparticles Using High-Precision STEM Imaging”, Microscopy and Microanalysis, 19 (S2), page 1688-1689 (2013).
  • A. B. Yankovich, B. Puchala, W. Fei, J.-H. Seo, D. Morgan, X. Wang, Z. Ma, A. V. Kvit, and P. M. Voyles, “Stable p-type conduction from Sb-decorated head-to-head basal plane inversion domain boundaries in ZnO nanowires”, Nano Letters, 12 (3) pp 1311-1316 (2012).
  • A. B. Yankovich, B. Puchala, F. Wang, D. Morgan, X. Wang, A. V. Kvit, and P. M. Voyles, “Head-to-head Inversion Domain Boundaries in Sb-doped p-type ZnO Nanowires”, Microscopy and Microanalysis, 18 (S2), page 316-317 (2012).
  • A. B. Yankovich, A. V. Kvit, H. Y. Liu, X. Li, F. Zhang, V. Avrutin, N. Izyumskaya, Ü. Özgür, H. Morkoç, and P. M. Voyles, “Pyramid nano-voids in GaN and InGaN”, SPIE OPTO, Vol. 8262-05 (2012).
  • A. B. Yankovich, A. V. Kvit, X. Li, F. Zhang, V. Avrutin, H. Y. Liu, N. Izyumskaya, U. Ozgur, H. Morkoç, and P. M. Voyles, “Absence of Lateral Composition Fluctuations in Aberration-corrected STEM Images of an InGaN Quantum Well at Low Dose”, Mater. Res. Soc. Symp. Proc., Vol. 1432 (2012).
  • A. B. Yankovich, B. Puchala, F. Wang, J.-H. Seo, D. Morgan, X. Wang, A. V. Kvit, Z. Ma, and P. M. Voyles, “p-Type Conduction in ZnO Nanowires from Sb-Decorated Head-to-Head Basal Plane Inversion Domain Boundaries”, Journal of Materials Science & Engineering, 1:3 (2012).
  • A. B. Yankovich, A. V. Kvit, X. Li, F. Zhang, V. Avrutin, H. Y. Liu, N. Izyumskaya, U. Ozgur, H. Morkoç, and P. M. Voyles, “Hexagonal-Based Pyramid Void Defects in GaN and InGaN”, Journal of Applied Physics, 111, 023517, (2011).
  • A. B. Yankovich, A. V. Kvit, X. Li, F. Zhang, V. Avrutin, H. Y. Liu, N. Izyumskaya, Ü. Özgür, H. Morkoç, and P. M. Voyles, “Indium Composition Variation in Nominally Uniform InGaN Layers Discovered by Aberration-Corrected Z-contrast STEM”, Microscopy and Microanalysis, 17 (S2), page 1386 (2011).
  • A. B. Yankovich, A. V. Kvit, X. Li, F. Zhang, V. Avrutin, H. Y. Liu, N. Izyumskaya, Ü. Özgür, H. Morkoç, and P. M. Voyles, “Vertical composition variation in nominally uniform InGaN layers revealed by aberration-corrected STEM imaging”, SPIE OPTO, Vol. 79391E, (2011)
  • N. Mevenkamp, P. Binev, W. Dahmen, P. M. Voyles, A. B. Yankovich, and B. Berkels, “Poisson Noise Removal from High Resolution STEM images based on Periodic Block Matching”, Advanced Structural and Chemical Imaging, accepted (2015).
  • N. Mevenkamp, A. B. Yankovich, P. M. Voyles and B. Berkels, “Non-local Means for Scanning Trnasmission Electron Microscopy Images and Poisson Noise based on Adaptive Periodic Similarity Search and patch Regularization”, Vision, Modeling, and Visualization, (2014).
  • N. Mevenkamp, R. Bergmann, B. Berkels, W. Dahmen, J. Mayer, P. M. Voyles, A. B. Yankovich, “Non-local Means based Denoising and Reconstruction of STEM Images”, Banff International Research Station for Mathematical Innovation and Discovery, (5/22/2015).
  • H. Y. Liu, N. Izyumskaya, V. Avrutin, Ü. Özgür, A. B. Yankovich, A. V. Kvit, P. M. Voyles, and H. Morkoç, “Donor Behavior of Sb in ZnO”, Journal of Applied Physics, 112(3), 033706 (2012).
  • H. Y. Liu, V. Avrutin, N. Izyumskaya, Ü. Özgür, A. B. Yankovich, A. V. Kvit, and P. M. Voyles, H. Morkoç, “Electron scattering mechanisms in GZO films grown on a-sapphire substrates by plasma-enhanced molecular beam epitaxy”, Journal of Applied Physics, 111, 103713 (2012).
  • A. V. Kvit, A. B. Yankovich, V. Avrutin, H. Liu, N. Izyumskaya, U. Ozgur, H. Morkoç, and P. M. Voyles, “Impurity Distribution and Microstructure of Ga-doped ZnO Films Grown by Molecular Beam Epitaxy”, Journal of Applied Physics, 112, 123527, (2012).
  • H. Y. Liu, X. Li, F. Zhang, V. Avrutin, N. Izyumskaya, Ü. Özgür, A. B. Yankovich, A. V. Kvit, P. M. Voyles, and H. Morkoc, “Electrical properties of ZnO:Ga as a transparent conducting oxide in InGaN based light emitting diodes”, SPIE OPTO, Vol. 8262-26 (2012).
  • B. Berkels, A. B. Yankovich, F. Shi, P. M. Voyles, W. Dahmen, R. Sharpley, P. Binev, “High Precision STEM Imaging by Non-Rigid Alignment and Averaging of a Series of Short Exposures”, Microscopy and Microanalysis, 18 (S2), page 300-301 (2012).
  • A. V. Kvit, A. B. Yankovich, B. T. Puchala, D. D. Morgan, P. M. Voyles, V. Avrutin, H. Liu, N. Izyumskaya, U. Özgür and H. Morkoç, “Structural and Elemental Analysis of Heavily- Doped ZnO”, Microscopy and Microanalysis, 18 (S2), page 392-393 (2012).
  • F. Wang, J.H. Seo, A. B. Yankovich, J. Shi, P. M. Voyles, Z. Ma, and X. Wang, “Sb-doped p-type ZnO nanowires: Solution synthesis, defects study, and device fabrication”, Abstracts of Papers of the American Chemical Society, 244 (2012).
  • H. Y. Liu, X. Li, S. Liu, X. Ni, M. Wu, V. Avrutin, N. Izyumskaya, Ü. Özgür, A. B. Yankovich, A. V. Kvit, P. M. Voyles, and H. Morkoç, “InGaN based light emitting diodes utilizing Ga doped ZnO as a highly transparent contact to p-GaN”, Physica Status Solidi (C), 8, 1548-1551 (2011).
  • H. Y. Liu, X. Li, S. Liu, X. Ni, V. Avrutin, N. Izyumskaya, Ü. Özgür, A. B. Yankovich, A. V. Kvit, P. M. Voyles, M. A. Reshchikov, and H. Morkoc, “Optimization of ZnO:Ga properties for application as a transparent conducting oxide in InGaN based light emitting diodes”, SPIE OPTO, Vol. 7939, 10, 79392E (2011).
  • H. Y. Liu, V. Avrutin, N. Izyumskaya, M. A. Reshchikov, S. Wolgast, C. Kurdak, A. B. Yankovich, A. V. Kvit, P. M. Voyles, Ü. Özgür, and H. Morkoc, “Effect of Growth Conditions on Electronic and Structural Properties of GZO Films Grown by Plasma-enhanced Molecular Beam Epitaxy on p-GaN(0001)/Sapphire Templates”, Mater. Res. Soc. Symp. Proc., Vol. 1315 (2011).

Conference Presentations

  • Contributed Presentation at the International Microscopy Congress (IMC) (2014), Prague Czech Republic, “Measuring atomic surface structures in Pt and Au nanocatalysts with high precision STEM imaging.”
  • Contributed Presentation at the pre-meeting congress on opportunities, artifacts, and interpretation of aberration-corrected electron microscopy data, Microscopy and Microanalysis (2014), Hartford CT, “Picometer-precision analysis of scanning transmission electron microscopy images.”
  • Post Presentation at Microscopy and Microanalysis (2014), Hartford CT, “Precision Limits to STEM Imaging from Dynamical Scattering and Channeling of Sub-Angstrom Electron Probes.”
  • Contributed Presentation at Banff International Research Station: Imaging and Modeling in Electron Microscopy and Mathematics (2014), Banff Canada, “Applications of non-rigid registration for enhanced signal to noise ratio, spatial precision, and standardless atom counting in STEM images.”
  • Contributed Presentation at Materials Research Society Spring Meeting (2014), San Francisco CA, “High precision STEM imaging of Pt and Au nanocatalysts.”
  • Contributed Presentation at Microscopy and Microanalysis (2013), Indianapolis IN, “Measuring Surface Atom Bond Length Contraction in Au and Pt Nanoparticles Using High-Precision STEM Imaging.”
  • Invited Speaker at OMICS Group Conferences: International Conference and Expo on Materials Science & Engineering, (2012), Chicago IL, “p-Type Conduction in ZnO Nanowires from Sb-Decorated Head-to-Head Basal Plane Inversion Domain Boundaries.”
  • Poster presentation at Gordon Research Conference: Defects in Semiconductors (2012), Biddeford ME, University of New England, “p-Type Conduction in ZnO Nanowires from Sb-Decorated Head-to-Head Basal Plane Inversion Domain Boundaries.”
  • Contributed Presentation at Microscopy and Microanalysis (2012), Phoenix AZ, “High Precision STEM Imaging by Non-Rigid Alignment and Averaging of a Series of Short Exposures.”
  • Contributed Presentation at SPIE Photonics West (2012), San Francisco CA, “Pyramid nano-voids in GaN and InGaN.”
  • Contributed Presentation at Microscopy and Microanalysis (2011), Nashville TN, “Indium Composition Variation in Nominally Uniform InGaN Layers Discovered by Aberration-Corrected Z-contrast STEM.”

Awards and Honors

  • Materials Research Society Silver Graduate Student Award (2014).
  • Microscopy Society of America (MSA) travel grant award for the 18th International Microscopy Congress (2014).
  • Accepted to participate in the IFSM School for young scientists at the 18th International Microscopy Congress (2014). (Declined due to personal circumstances)
  • University of Wisconsin – Madison Vilas Foundation Conference Travel Grant for presenting at the International Microscopy Congress (2014).
  • Microscopy and Microanalysis Presidential Scholar Student Award (2013).
  • Invited Speaker: OMICS International Conference and Expo on Material Science & Engineering, Chicago IL (2012).
  • Accepted to participate in the Canadian Center for Electron Microscopy’s summer school on aberration-corrected electron microscopy, McMaster University (2010).