Our research focuses on atomic-level analytical electron microscopy and spectroscopy. To reach essential science for materials development, we have to keep pursuing to find the key factors to control material properties. Most of these factors, which have not been well understood, are “subtle features” inside the materials. For example, optical and electronic properties from doped nanocrystals are mainly governed by the position and chemical state of dopants, and only full understanding of those individual dopant atoms can lead us to achieve desired properties from the materials. The challenge to unveil the origin of many material properties is primarily associated with the lack of understanding of the subtle features such as interfaces, defects, doping, and strains. Scanning transmission electron microscopy (STEM) is no doubt one of the techniques to visualize the subtle feature with enough precision and resolution. We are conducting extensive sub-Å-resolution microscopy and spectroscopy studies to understand these subtle features, establish fundamental knowledge of them, and get desired material properties.
- Atomic-level characterization of materials using analytical scanning transmission electron microscopoy (STEM)
- Quantitative analysis of defects, interfaces, dopants, strain and magnetic and electric field in low-dimensional materials
- Electron energy-loss spectroscopy (EELS), Energy dispersive spectroscopy (EDS), and STEM annular dark-field (ADF) imaging
- Electron holography
- Electron and X-ray crystallography
- Eric Samuel Scholarship, The Microscopy Society of America, 2014
- Moam Scholarship, 1996-1999
- J. S. Jeong, M. Topsakal, P. Xu, B. Jalan, R. M. Wentzcovitch, K. A. Mkhoyan, “A New Line Defect in NdTiO3 Perovskite,”
Nano Lett. 16(11), 6816-6822 (2016).
- J. S. Jeong, M. L. Odlyzko, P. Xu, B. Jalan, K. A. Mkhoyan, “Probing core-electron orbitals by scanning transmission electron microscopy and measuring the delocalization of core-level excitations,”
Phys. Rev. B 93(16), 165140 (2016).
- J. S. Jeong, K. A. Mkhoyan, “Improving Signal-to-Noise Ratio in Scanning Transmission Electron Microscopy Energy-Dispersive X-Ray (STEM-EDX) Spectrum Images Using Single-Atomic-Column Cross-Correlation Averaging,”
Microsc. Microanal. 22(03), 536-543 (2016)..
- S. Y. Kim, J. S. Jeong, K. A. Mkhoyan, H. S. Jang, “Direct observation of core/double-shell architecture of intense dual-mode luminescent tetragonal bipyramidal nanophosphors,”
Nanoscale 8(19), 10049 (2016).
- P. Xu, T. C. Droubay, J. S. Jeong, K. A. Mkhoyan, P. V. Sushko, S. A. Chambers, B. Jalan, “Quasi 2D Ultrahigh Carrier Density in a Complex Oxide Broken-Gap Heterojunction,”
Adv. Mater. Interf. 3, 1500432 (2016).
- M. Jamali, J. S. Lee, J. S. Jeong, F. Mahfouzi, Y. Lv, Z. Zhao, B. K. Nikolić, K. A. Mkhoyan, N. Samarth, J.-P. Wang, “Giant Spin Pumping and Inverse Spin Hall Effect in the Presence of Surface Spin-Orbit Coupling of Topological Insulator Bi2Se3,”
Nano Lett. 15(10), 7126-7132 (2015).
- A. S. George, Z. Mutlu, R. Ionescu, R. J. Wu, J. S. Jeong, H. H. Bay, Y. Chai, K. A. Mkhoyan, M. Ozkan, C. S. Ozkan, “Wafer Scale Synthesis and High Resolution Structural Characterization of Atomically Thin MoS2 Layers,”
Adv. Funct. Mater. 24(47), 7461-7466 (2014).
- L. Zhang, Y. Meng, W. Yang, L. Wang, W. L. Mao, Q.-S. Zeng, J. S. Jeong, A. J. Wagner, K. A. Mkhoyan, W. Liu, R. Xu, H.-K. Mao, “Disproportionation of (Mg,Fe)SiO3 into MgSiO3 perovskite and an Fe-rich hexagonal silicate in the deep lower mantle,”
Science 344(6186), 877-882 (2014).
- H. Na, J. S. Jeong, H. J. Chang, H. Y. Kim, K. Woo, K. Lim, K. A. Mkhoyan, H. S. Jang “Facile synthesis of intense green-emitting LiGdF4:Yb,Er-based upconversion bipyramidal nanocrystals and their polymer composites,”
Nanoscale 6(13), 7461-7468 (2014).
- J. S. Jeong, P. Ambwani, B. Jalan, C. Leighton, K. A. Mkhoyan, “Observation of Electrically-Inactive Interstitials in Nb-Doped SrTiO3,”
ACS Nano 7(5), 4487-4494 (2013).
- J. S. Jeong, Y. Murakami, D. Shindo, H. Kawase, “Investigation of tribocharges and their migration in layered model toners by electron holography,”
J. Appl. Phys. 109(12), 124903 (2011).
- J. S. Jeong, Z. Akase, D. Shindo, Q. Zhan, K. M. Krishnan, “Electron holography study of remanence states in exchange-biased MnPd/Fe bilayers grown epitaxially on MgO(001),”
J. Electron Microsc. 60(3), 235-242 (2011).