Jeong Group Research Areas
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. Our research areas cover several different fields in electron microscopy including:
- 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
Current Projects
- Interface asymmetry in polar/non-polar complex oxides
- Interfacial properties of ultra-thin functional oxides films
- Strain effect on electronic density of states
- Distribution and luminescent properties of Ln ion-doped inorganic nanophosphors
- Structure and reactivity of 2D WS2 and MoS2 single sheet
Electron Microscopes and Facilities
Monochromated and Aberration-Corrected FEI Titan G2 60-300 STEM
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Shepherd Labs Facility
- Operational at 60, 80, 200, and 300 keV
- Probe corrected: spatial resolution of 0.063 nm at 300 keV
- Four image detectors: HAADF, DF1, DF2, adn BF
- ChemiSTEM EDX
- Gatan Enfinium EELS
- Gatan Ultra1000XP 2k x 2k CCD
- Remote operation
FEI Tecnai G2 F3 STEM
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Shepherd Labs Facility
- Operational at 50-300 keV
- Point-point resolution of 0.20 nm with information limit of 0.14 nm
- ADF-STEM with resolution of 0.19 nm
- EDAX rTEM EDX
- Gatan Enfina EELS
- Gatan UltraScan 2k x 2k CCD
FEI Tecnai G2 F3 Cryo STEM
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Nils Hasselmo Hall Facility
- Operational at 50-300 keV
- Point-point resolution of 0.24 nm with information limit of 0.15 nm
- Fully computer controlled high stability CompuStage and up to 70° eucentric tilt
- Gatan GIF 2002 EELS
- Gatan UltraScan 4k x 4k CCD and Gatan 692 tv-rate CCD positioned behind GIF
- Xplore 3D and Amira software for TEM Tomography (For 3D reconstruction of TEM images)
FEI Tecnai T12
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Shepherd Labs Facility
- Operational at 20-120 keV
- Point-point resolution of 0.34 nm; line resolution of 0.2 nm
- Oxford Inca EDX
- Gatan MSC794 1k x 1k CCD
- Gatan 692 tv-rate CCD
TEM holders
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Shepherd Labs Facility
- single- and double-tilt holders
- Gatan heeting holders
- Protochips Aduro heating and electric holder
- Cryo and tomography holders
Fischione 1010 Ion Mill
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Shepherd Labs Facility
- Fully programmable and easy to use
- Adjustable rocking angle
- LN2 specimen cooling
Gatan Precision Ion Polishing System (PIPS)
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Shepherd Labs Facility
- Ion milling at a very low, but variable angle
- Milling monitoring system
- Minimum of differential milling-rate artifcats
Fischione 1020 Plasma Cleaner
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Nils Hasselmo Hall Facility
- Fully programmable gas flow, power, and time
- Removes existing carbonaceous contamination
- Storage in clean vacuum
Fischione 1070 NanoClean Plasma Cleaner
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Shepherd Labs Facility
- Fully programmable gas flow, power, and time
- Load-locked for fast holder insertion and removable
- Large-sample access door for cleaning of large samples
- Multiple gas inlets with mixing capabilities
Allied MultiPrep Polishing System
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Shepherd Labs Facility & Amundson Hall 454 Lab
- Utilized primarily for preparation of wedge specimens
- Front digital indicator to display real-time material removal (sample advancement), 1 µm resolution
- Multiple polishing pads and lubricants available
- Controlled angular positioning of the sample
- Automatic sample oscillation, adjustable sweep with 6 speeds
- Variable sample load: 0-600 g (100 g increments)
Ultra-High Vacuum Heating System
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Shepherd Labs Facility
- Heating up to 190 oC
- Fully programmable temp. and time
- TEM grids loading system
Other instruments in CharFac
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http://www.charfac.umn.edu
- Atomic Force Microscopy (AFM) & related
- Scanning Electron Microscopy (SEM)
- Surface and Thin-film Analysis
- Vibrational Spectroscopy
- Visible Light Microscopy
- X-ray Diffraction & Scattering
