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Chhowalla Group Research
Gold Nanoparticles (acquired by UltraSTEM)
hybrid perovskite single crystals
rubrene OFETs
Professor Shahab Shojaei-Zadeh publishes in Phys Rev Fluids
Fabris Group Research

Aberration Corrected Imaging

Since the invention of electron optics during the 1930’s, lens aberrations have limited the achievable spatial resolution to about 50 times the wavelength of the imaging electrons. Positive spherical aberration is unavoidable in a magnetic lens having cylindrical symmetry. The simplest way to compensate for this problem is to employ sets of multipole lenses to produce a negative spherical aberration correction. The difficulty is that these multipole lenses need to be matched in position, orientation and tilt to the original lens, leading to very complex systems of 30-100 optical elements that need to be controlled with parts per million accuracy. Thus aberration correction has only recently becomes possible -- enabled by advances in design of electron optics and by the availability of highly stable electronics and inexpensive computer platforms for control of the many optical elements. [1]

aberr002 aberr003


On the left: Improvement of performance in the STEM with the addition of aberration correction. [2] The left side shows results for the objective lens transmission as a function of angle ( a shadow map or Ronchigram), the resulting 2Å resolution image, and the frequencies. The signal contrast is now high enough to image individual heavy atoms and their movement as they form a cluster, as shown on the right. [3]

[1] M. Haider, S. Uhlemann, E. Schwan, H. Rose, B. Kabius, and K. Urban, Electron microscopy image enhanced, Nature 392, 768-769 (1998).

[2] P.E. Batson, Niklas Dellby, and O.L. Krivanek, Sub-Angstrom resolution using aberration corrected electron optics, Nature 418, 617-620 (2002).

[3] P.E. Batson, Challenges and Opportunities of Angstrom-Level Analysis, in Microscopy of Semiconducting Materials, edited by A.G. Cullis (Royal Microscopy Society, Oxford, 2005), pp. 836-837.

Baston Research

Batson Nano-Scale Discovery Collaboration

About Us

Collaborations

Highlights

Publications

History

Scanning Transmisson Electron Microscopy

P.E. Batson and M.J. Lagos

We can now make an electron beam that is about the size of a hydrogen atom, and can actually place that beam on or between atoms within materials to examine how they are put together, how they might function in a device, how they might be used to measure biological activity, or hasten a chemical reaction.  The image above shows the positions of columns of atoms in an interface between two metal oxide structures.We also can perform very simple experiments to understand how materials, in general, act at very short times.  Atoms and molecules move about and vibrate at very high speeds.  We can now, for the first time, visualize the behavior of very small structures at atto-second time scales in an electron microscope, and plan experiments to test these ideas. The film clip at the upper right is a calculation of the forces acting on a 2 nm-sized gold sphere during the passage of a fast electron in the STEM.  These forces change dramatically during a few atto-seconds, inducing changes in the nano-particle that inform us about how such structures might be used for energy-gathering, catalysis and information transfer.  


Much slower behavior, the transport of heat from one part of a specimen to another, can be understood with this instrument as well.  Measuring  energy changes within a specimen to an accuracy of 10 milli-eV, corresponding to pico-second  timescales, allows us to characterize phonon behavior in nano-scale structures. The middle figure shows how the phonon signal in silicon dioxide at 150 meV changes as the electron beam  is moved across a semiconductor sample.        

The new instrument is a Nion UltraSTEM 100 kV STEM with the Hermes  electron monochromater.  We are now operating at 60 kV beam energy and  obtain Angstrom level images with 10 meV beam energy resolution  using about 20 pico-amps of current.  The new  STEM is housed in a room having very low noise intereference -- electrical, magnetic, floor vibration, acoustic, and temperature.  

At Rutgers we are exploring practical materials with new collaborations, but also wondering about “What if …” questions whose ultimate use we can only imagine. 

We acknowledge the financial support of the Department of Energy,  Basic Energy Sciences (DOE project #DE-SC0005132) for work on Electron Beam Induced Forces, and the National Science Foundation MRI #0959905 for the instrumental development.

Atto-Second Forces during the passing of a swift electron.

Atto-Second Forces during the passing of a swift electron.

Phonon Spectra in SiO2 at ~150 meV

 

Nion UltraSTEM at Rutgers

Developing and Utilizing Top-down and Bottom-up Nanotechnology approaches for Cell Biology

Program: Nanobiology
Department: Chemistry and Chemical Biology

The primary research interest of our group is to develop and integrate nanotechnologies and chemical functional genomics to modulate signal pathways in cells (e.g. stem cells and cancer cells) towards specific cell lineages or behaviors. In particular, we are interested in studying the function of microenvironmental cues (e.g. soluble signals, cell-cell interactions, and insoluble/physical signals) towards stem cell and cancer cell fate. In order to investigate the functions of microenvironmental cues that affect stem or cancer cell behaviors, we inevitably require an ability to emulate microenvironmental systems in vitro and assay responses of cells to these multiple signals. Recognizing how cell behaviors are controlled by the microenvironmental cues is, however, much more complex. Studying the complicated cell behaviors necessitate, at minimum, two abilities: i) to precisely control the features of the microenvironment that affect cell behaviors and ii) to probe stem cell responses to multiple cues at the single molecule level. For example, both approaches from nanotechnology-the "top-down" pattering of extracellular matrix (ECM) and signal molecules in combinatorial ways (e.g. ECM compositions, pattern geometry, pattern density, and gradient patterns), and the "bottom-up" synthesis of multifunctional nanoparticles and their modification with specific signal molecules-should be combined synergistically, if the complex cell behaviors are to be fully investigated. Collectively, our research program is directly relevant to matters concerning biomaterials, nanomedicine, chemical biology and stem/cancer cell biology.

Major Research Topics:Biosurface engineering at the micro-/nanoscale (Top-down approach), Nanomaterial synthesis and their functionalization (bottom-up approach), Stem cell & cancer cell biology



Research Topic 1. Biosurface engineering at the micro-/nanoscale

 

 
 

Research Topic 2. Synthesis and utilization of multi-functional nanomaterials for molecular imaging and drug delivery

 

 


Research Topic 3. Modulating signaling pathways and probing biological interactions

Dynamic Movement of Atoms

movingAu001

The discussion above about formation of a cluster of Au atoms implies that some atomic motion is visible. This is indeed the case for beam currents above about 100 picoAmp. The example to the right is a display of several frames at approximately real time. (5 fps) The Au atoms can be seen to move about each other and to form what look like three dimensional structures. The power spectrum of the image is displayed in the upper right. From time to time it shows lattice periodicities which are characteristic of a Au crystal. Since atoms sometimes remain unmoved, sometimes move a small amount, and sometimes move large distances, it appears that the distance which is moved is probably controlled by available binding sites, while the rate of movement is controlled by the beam excitation. In the upper middle, two atom images appear to coalesce, possibly implying that this is really only one atom which rapidly explores two binding sites, so that it appears twice in the same image.

Early Stages Of Diseases In Mineralized Tissues

Program: Nanobiology
Department: Materials Science and Engineering

Electronics, Photonics and Sensors

IAMDN researchers have dynamic programs in areas that will impact future electronics, photonics and sensors. Organic electronics promise low-cost, large area applications varying from flexible display technology to light harvesting. One Rutgers team is studying basic mechanisms of charge transport and has obtained the highest mobility (speed) organics in the world, setting a new milestone in this burgeoning technology. In nanoelectronics, we have a nationally leading team focused on the growth, characterization and computational modeling of next generation transistor materials. A device-oriented set of projects with broad applications in sensors, power electronics/energy efficiency and telecommunications involve wide bandgap semiconductors, especially ZnO and SiC. Entirely new approaches are underway in the creation of innovative emergent oxide materials with potential applications that combine optics, magnetics and piezoelectricity. Rutgers facilities for this demanding research are currently considered “best in the world”, and anchor extraordinary materials innovation. A new and exciting set of projects involve implementations of quantum computing, a futuristic approach to computation that may revolutionize information processing. Other projects include micro/nano-photonics for high-speed optical communication, MEMS, sensor for bio-mechanical applications and other nanostructured materials. Our experimental teams are supported by an excellent arsenal of surface and bulk synthesis and characterization tools within the Rutgers Laboratory for Surface Modification, the Microelectronics Research Laboratory and the Center for Ceramics Research, and interact closely with very strong computational teams, including those in the world leading Center for Materials Theory.
 
 

 

Research TitleResearcher NameEmailHome Page
Atomic-layer-engineered oxide-metamaterials for novel functionality Seongshik (Sean) Oh This email address is being protected from spambots. You need JavaScript enabled to view it. Link
Catalytic Flame Synthesis of Carbon Nanotubes Stephen Tse This email address is being protected from spambots. You need JavaScript enabled to view it. Link
Design and Characterization of WGM NEMS Resonators for Nanoscopic Sensing Zhixiong Guo This email address is being protected from spambots. You need JavaScript enabled to view it.
Nano-Materials and Devices Manish Chhowalla This email address is being protected from spambots. You need JavaScript enabled to view it. Link
Organic Electronics and Functional Inorganic Electronic Devices Vitaly Podzorov This email address is being protected from spambots. You need JavaScript enabled to view it. Link
Photonic Crystals, Silicon Photonics, and Nanophotonics Wei Jiang This email address is being protected from spambots. You need JavaScript enabled to view it. Link
Superconducting Nanocircuits for Topologically Protected Qubits Michael Gershenson This email address is being protected from spambots. You need JavaScript enabled to view it. Link
Nanophotonics for Organic Optoelectronics Deirdre O'Carroll This email address is being protected from spambots. You need JavaScript enabled to view it. Link
Invisible Dopants Mona Zebarjadi This email address is being protected from spambots. You need JavaScript enabled to view it. Link

Energy and Environment

IAMDN promotes and supports interdisciplinary research activities at Rutgers in fields that address sustainability in energy and environment. Coupled closely with local industry, IAMDN research in batteries and supercapacitors directly addresses energy storage and energy efficiency. In solar technologies, over one dozen faculty carry out innovative research in photovoltaics (PVs), focusing on dye-sensitized inorganic materials, nanotubes/nanowire-enhanced organic PVs, and basic studies of high purity crystalline organic PV materials - all addressing a more efficient and low-cost photovoltaics. A third set of projects explore novel materials for hydrogen storage and fuel cells. Catalysis strongly affects the energy problem – one study considers the structure and function in designer nano-catalysts, another focuses on metathesis catalysts for efficient diesel production. “Green chemistry” projects involving chemical synthesis, environmental remediation and CO2 sequestration add important elements to the expanding energy research agenda at Rutgers. The IAMDN interacts closely with the Rutgers Energy Institute and the Energy Storage Research Group in this exciting and critically relevant area.

 

 

Research TitleResearcher NameEmailHome
HOMO and LUMO energies of N3 dye on TiO2(110) Bartynski, Robert A. This email address is being protected from spambots. You need JavaScript enabled to view it.
New Materials for Energy Storage and Conversion Li, Jing This email address is being protected from spambots. You need JavaScript enabled to view it. Link
Hybrid Energy Systems and Materials Cook-Chennault, Kimberly This email address is being protected from spambots. You need JavaScript enabled to view it. Link
Electron and Excitation Transfer in Host-Guest Supramolecular Assemblies Piotrowiak, Piotr This email address is being protected from spambots. You need JavaScript enabled to view it. Link

Monochromator Project

Although the EELS spectrometer in this system delivers an energy resolution of about 50-130meV, the natural width of the room temperature Field Emission Gun (FEG) electron source is 280-350 meV, so a full utilization of the spectrometer capability is limited. This can be changed by addition of an electron monochromator, placed within the gun. A 3 cm long “fringe field” monochromator has been designed and tested for this system. [1, 2] This device disperses the FEG source electrons against a 200 nm diameter aperture. The monochromator-spectrometer combination has shown a 61 meV resolution, while preserving the high brightness characteristics of the FEG. The left illustration below shows the intensity of the gun as the source spot is scanned across the small energy selecting aperture.

mono004 mono006


[1] P.E. Batson, H.W. Mook, and P. Kruit, High Brightness Monochromator for STEM, in International Union of Microbeam Analysis 2000, edited by D.B. Williams and R. Shimizu (Institute of Physics, Bristol, 2000), Vol. 165, pp. 213-214.

[2] H.W. Mook, P.E. Batson, and P. Kruit, Monochromator for high brightness electron guns, in 12th European congress on electron microscopy, Vol. III, (2000) pp. 315 -316.

Nano-biology: Single-molecule DNA Nanomanipulation and Single-molecule Fluorescence

Program: Nanobiology
Department: Chemistry and Chemical Biology
Collaborator: Terence Strick, Department of Physics, University of Paris
By monitoring the overall extension of a mechanically stretched, negatively supercoiled, single DNA molecule containing a single target site, we are able to observe the gain of ~1 positive supercoil, or loss of ~1 negative supercoil, associated with protein-induced unwinding of ~10 base pairs of the target site.1 The assay enables us to define--at the single-molecule level, in real time the extent of unwinding, the kinetics of unwinding, and the lifetime and dynamics of the unwound state. In addition, the assay enables us to define effects of DNA sequence, supercoiling, temperature, and small molecule modulators.

We are working to develop single-molecule-nanomanipulation and combined single-molecule-nanomanipulation/single-molecule-fluorescence approaches for systematic structural and mechanistic analysis of nucleic-acid processing enzymes, to automate the approaches, and to apply the approaches to drug discovery.

  1. Proc. Natl. Acad. Sci. USA, 101:4776-4780 (2004).

Nanobiology

IAMDN supports projects throughout Rutgers that bridge the interface between the materials and life sciences. IAMDN facilities resources have equipped research teams with state-of-the-art micro- and nano-patterning and lithography facilities for applications in micro- and nano-fluidics and tissue engineering. We support several groups in nanomedicine, with expertise in nano-scale pharmaceuticals and nano-scale drug delivery systems. Other coupled research programs are focused on molecular/cellular mechanism and motor problems in nanobiology, and energy exchange and harvesting. Underpinning this research is active development of nanosynthesis, nanoparticle and nano-characterization capabilities. In addition, IAMDN provides advanced spectroscopic and microscopic characterization facilities to support several Centers including the NSF-ERC for Structure Organic Particulate Systems (C-SOPS), the NJ Center for Biomaterials, EOSHI, UMDNJ, the Cancer Institute of NJ, and the Stem Cell Institute of NJ.

 

 

Research TitleResearcher NameEmailHome Page
Developing and Utilizing Top-down and Bottom-up Nanotechnology approaches for Cell Biology Lee, KiBum This email address is being protected from spambots. You need JavaScript enabled to view it. Link
Early Stages Of Diseases In Mineralized Tissues Mann, Adrian This email address is being protected from spambots. You need JavaScript enabled to view it. Link
Nano-biology: Single-molecule DNA Nanomanipulation and Single-molecule Fluorescence Ebright, Richard This email address is being protected from spambots. You need JavaScript enabled to view it. Link
Polymeric Micelles Uhrich, Kathryn E. This email address is being protected from spambots. You need JavaScript enabled to view it.
SERS-based Cell Imaging Fabris, Laura This email address is being protected from spambots. You need JavaScript enabled to view it. Link
Organic Materials for Electronics and Photonics Garfunkel, Eric This email address is being protected from spambots. You need JavaScript enabled to view it. Link
Complex Fluids and Soft Matter Shojaei-Zadeh, Shahab This email address is being protected from spambots. You need JavaScript enabled to view it.
Link
Cell Therapy Olabasi, Ronke This email address is being protected from spambots. You need JavaScript enabled to view it. Link

New Faculty

NameResearch InterestsResearch Page
Asefa, Tewodros (Teddy) (1) the design, synthesis, and self-assembly of novel inorganic nanomaterials and organic-inorganic hybrid nanostructured and nanoporous materials and nanobiomaterials; (2) catalysis and nanocatalysis; (3) nanomaterials for biological, medical, and biosensing applications; and (4) nanomaterials for solar cell applications. Link
Batson, Philip Spatially resolved Electron Energy Loss Spectroscopy (EELS) using the Scanning Transmission Electron Microscope (STEM) Link
Blumberg, Girsh Experimental Condensed Matter Physics; Strongly Correlated Electron Systems; Superconductivity; Quantum magnetism; Optical spectroscopy; Applications of photonics; Plasmonics and Opto-Electronics Link
Celler, George K. Electronic materials – processing and characterization. Heterogeneous integration of single crystalline SiC with other electronic substrates. Semiconductor-on-Insulator formation and applications (electronic, photonic, MEMS). Wafer bonding and ion-beam assisted layer transfer. Integrated photonics and optical communications. Photovoltaic materials and devices. Laser processing of materials. Advanced lithography (beyond optical). Link
Cook-Chennault, Kimberly Hybrid Battery Systems; Energetic Composites and Devices Link
Fabris, Laura Synthesis and characterization of nanoparticles and their controlled aggregation; nanoparticles for the preparation of materials with tailored properties; nanoparticles in nanobiotechnology Link
G Charles Dismukes Biological and chemical methods for renewable solar-based fuel production, photosynthesis, metals in biological systems and tools for investigating these systems. Link
Jeon, Jaeseok Nano-electro-mechanical relay devices and technology for energy-efficient electronics; Neural relay devices for efficient design and implementation of neuromorphic systems; Advanced materials and process technology for energy-harvesting devices  
Jiang, Wei developing novel photonic devices for communications, sensing, beam steering and other applications Link
Lai, Warren micro- and nano-fabrication for applications in IC, electronics, photonics, MEMS, sensors and nanotechnology, including advanced process development, novel device integration, material engineering, metrology, characterization, reliability and manufacturability

Link

Lee, KiBum Develop and integrate nanotechnologies and chemical functional genomics Link
O'Carroll, Deirdre M. Nanoscale engineering of light generating and light harvesting processes in photonic devices which employ organic polymeric semiconductor materials and plasmonic nanostructures Link
Oh, Seongshik Nano-scale heterostructure engineering Link
Olabisi, Ronke Orthopedic tissue engineering and regenerative medicine for injury, disease, and space flight. Link
Podzorov, Vitaly V. High performance single-crystal organic field-effect transistors (OFETs). Understanding the fundamentals of charge carrier transport and photo-physical properties of organic semiconductors Link
Shahab Shojaei-Zadeh Small Scale Fluid Dynamics; Interfacial Phenomena; Soft Condensed Matter; Nanoscale Science and Technology with Applications in Biomedicine, Energy Systems, and the Environment. Link
Zebarjadi, Mona Renewable Energies, Solid State Energy Conversion, Materials Design, NanoScale Heat and Electricity Transport. Link

Nion Aberration Corrector

The Nion Aberration Corrector consists of seven elements – four quadrupoles (red) and three octupoles (blue) – placed between the two condenser lenses (bottom) and the objective lens (top) of the VG Microscopes HB501 STEM. [1] The quadrupoles shape the beam into pencil cross sections inside the octupoles. The octupoles then provide correction for spherical aberration in the objective lens. Summing the octupole strengths (on the left) shows that there is a net +1 strength in both the x-z and y-z planes. The corrector is installed into the volume previously occupied by scan coils, under the objective lens. Electrical and mechanical stabilities of 0.2 ppm are crucial to the successful operation of this device. The image on the right shows the corrector hardware mounted underneath the microscope objective lens.

corrector002 corrector003


[1] N. Dellby, O.L. Krivanek, P.D. Nellist, P.E. Batson, and A.R. Lupini, Progress in Aberration-corrected Scanning Transmission Electron Microscopy, J. Electron Microscopy 50, 177-185 (2001).

Podzorov Research

Click here to visit the Podzorov Group Page.

Hybrid perovskite single crystals. Hybrid perovskites have become the subject of an intense research worldwide for their use in solar cells. Our group here at Rutgers has performed the first Hall effect studies of intrinsic charge carrier mobility and carrier recombination dynamics in these important class of materials. The paper appeared in Nature Comm. on Aug. 1, 2016. 
Ref.: Y. Chen et al., Nature Comm. DOI: 10.1038/ncomms12253 (2016). 

 

Research Associate Hee Taek Yi and Prof. Vitaly Podzorov in the lab, working on organic and flexible electronics.

5 Podzorov and Yi in the lab

 

Molecular structure of Rubrene, the benchmark organic semiconductor used for fundamental and applied research in Organic Electronics, whose amazing electronic properties were discovered at Rutgers.

6 rubrene molecule

 

Organic single-crystal field effect transistors based on Rubrene (OFETs). Rubrene OFETs, developed for the first time at Rutgers, represent the highest performance organic electronic devices to date.

7 rubrene OFET for Hall measurements

8 rubrene OFET

Polymeric Micelles

Program: Nanobiology
Department: Chemistry and Chemical Biology

Research at the Institute

Rutgers has become a global leader in advanced nanoscale materials imaging, bringing to the New Jersey region a new resource for the advancement of scientific research, educational outreach and industrial partnership. We have the beginning of a Rutgers imaging institute through IAMDN that will foster international scientific collaboration to significantly impact research in biomaterials, medical research of cancer and neurology, renewable energy, and telecommunications. These microscopes are without question the most advanced devices utilized in the world today to visualize the atomic structure of new nanoscale materials. The advances they support will empower researchers confronting some of the most daunting global problems today.
 
The Institute provides support, coordination and oversight for three large groups of research programs in the areas of Energy and Environment (E&E), Electronics, Photonics and Sensors, (EPS), and Nanobiology (NB). 
 

 
 
Rutgers Institute for Advanced Materials, Devices and Nanotechnology (IAMDN) Scanning Transmission Electron Microscope (STEM) with meV resolution Electron Energy Loss Spectroscopy (EELS) can visualize the atomic structure of new materials, and explore composition, bonding, electronic and vibrational energy scales to enable better materials designs for efficient energy production and storage, catalysis, nanoelectronics and photonics.


 
 
The Rutgers Institute for Advanced Materials, Devices and Nanotechnology (IAMDN) Helium Ion Microscope is a novel instrument for imaging surfaces with sub-nm resolution and unprecedented depth of view. Non-conducting samples can be probed without metallic coatings, and samples can be modified and new structures can be formed by ion irradiation. Potential applications include advances in fields from drug delivery and the creation of orifices to explore DNA sequencing to the formation of quantum structures for advancing computing and communications.
 

Spatially Resolved EELS

sreels003 sreels002

 

Above: Annular Dark Field (ADF) Imaging and Electron Energy Loss Spectroscopy (EELS) analytical techniques. In ADF imaging, electrons in the beam undergo large angle elastic scattering when they pass close to atoms within the specimen. These electrons are caught by an annulus detector, generating a signal used to form a scanned image -- displayed at the top in the right figure for a probe size of 2 Å in GeSi. Electrons which undergo only small angle deflection also lose some energy to the specimen. An Electron Spectrometer separates these electrons according to their energy, producing Electron Energy Loss Spectra. The spectra in the lower right summarize the silicon 2p core absorption edge at 99.86 eV for various locations in the image. The detailed shape of this edge can be interpreted in terms of the conduction bands in the Ge30Si70 specimen. [1] Since ADF imaging provides a very direct simple representation of the specimen structure, it can usually be compared with structural model calculations as indicated in the lower left image. (Model structure from Chelikowski. [2])

[1] P.E. Batson, Atomic Resolution Electronic Structure in Silicon-Germanium Alloys, J. Electron Microscopy 45, 51-58 (1996).

[2] P.E. Batson, Structural and Electronic Characterization of a Dissociated 60° Dislocation in GeSi, Phys. Rev. B 61, 16633-16641 (2000).

Spectrometer Description

spect002

The EELS spectrometer is a Wien Filter type mounted within a high voltage electrode.[1,2] The filter is designed for a center pass energy of 100-200 eV, giving it a very high energy dispersion -- of order mm/eV. This center pass energy is defined by a very accurate 15-1200V scanning power supply which is in turn connected to the microscope high voltage. This design is capable of about 60 meV energy resolution at a collection half angle of 10 mR at the specimen, and a center pass energy definition of better than 20 meV. In the figure below, I show a design intended to optimize the spectrometer for operation with the aberration corrected probe.[3] The Wien Filter has a first order focus in the energy dispersive direction, but does not modify the electron paths in the perpendicular direction. Therefore we use a combination of a cylindrical lens and a weak quadrupole to produce focusing in the energy dispersive direction and to maintain a narrow beam in the spectrometer in the other direction. This design suggests that a 15 meV resolution should be possible using 15 mR collection half angle at the specimen.

 

spect004


[1] P.E. Batson, High Resolution Electron Energy Loss Spectrometer for the Scanning Transmission Electron Microscope, Rev. Sci. Inst. 57, 43-48 (1986).

[2] P.E. Batson, Parallel Detection for High Resolution Electron Energy Loss Studies in the Scanning Transmission Electron Microscope, Rev. Sci. Inst. 59, 1132-1138 (1988).

[3] P.E. Batson, High Resolution Spectrometer Coupling to the Sub-Angstrom IBM STEM, in Microscopy and Microanalysis, edited by D. Piston, J. Bruley, I.M. Anderson, P. Kotula, G. Solorzano, A. Lockey, and S. McKernan (Cambridge University Press, Cambridge, 2003), pp. 836 -837.

STEM-EELS Introduction

GaN002 0The STEM was conceived and first built by Albert Crewe in the late 1960’s at the University of Chicago. [1] He realized that an electron microscope equipped with a high brightness field emission electron gun would be able to create an atom-sized electron beam. Using beam energies of 100-300 KeV, the bulk structure of nanometer sized specimen areas can be examined with very high magnification. This examination can use several analytical signals: large angle elastic scattering -- Annular Dark Field (ADF) imaging; small angle elastic scattering -- Bright Field (BF) imaging; small angle inelastic scattering -- Electron Energy Loss Spectroscopy (EELS); characteristic x-ray production -- Energy Dispersive X-Ray spectroscopy (EDS); and many others. At IBM, Philip Batson has used a VG Microscopes STEM to explore Spatially Resolved EELS techniques using the very small probe. In order to examine energy scales relevant to semiconductor operation, Batson built a high resolution electron spectrometer in 1986. Achieving 70 meV resolution with an absolute accuracy of 20 meV at 120 KeV beam energy, this instrument has been a leader in EELS spectroscopy of nanoscale areas. Recently, in collaboration with O. Krivanek and N. Dellby of Nion Co., aberration correction optics were successfully incorporated in the IBM STEM, allowing a sub-Angstrom sized electron beam to be created for the first time. [2] Finally, with P. Kruit and W. Mook of the Technical University of Delft, an electron monochromator has been constructed for the VG STEM. With this device the energy line width of the electron beam will be reduced from 300 meV to 60 meV, using electron optics designed to minimize loss of brightness which would compromise the ability to make a sub-Angstrom probe. [3]

Image: Aluminum Nitride: The relative positions of Al columns (red) and N columns (blue) determine the electrical polarization direction.[4]

[1] A.V. Crewe, M. Isaacson, and D. Johnson, A Simple Scanning Electron Microscope, Rev. Sci. Inst. 40, 241-246 (1969).

[2] P.E. Batson, Niklas Dellby, and O.L. Krivanek, Sub-Angstrom resolution using aberration corrected electron optics, Nature 418, 617-620 (2002).

[3] H.W. Mook, P.E. Batson, and P. Kruit, Monochromator for high brightness electron guns, in 12th European congress on electron microscopy, Vol. III, (2000) pp. 315 -316.

[4] K.A. Mkhoyan, P.E. Batson, J. Cha, W.J. Schaff, and J. Silcox, Direct Determination of the Local Polarity in Wurzite Crystals, Science 312, 1354 (2006).

The IBM Instrument

IBM STEM001 IBM STEM002

 

In the line drawing on the left, we see that the IBM VG Microscopes STEM has the electron gun at the bottom. Above that are a set of lenses which focus the beam to 0.08 nm at the specimen. Beyond the specimen, there are two major detectors – 1) an annulus for sensing electrons which have scattered to large angles by interaction with an atom or atom column, and 2) an electron energy loss spectrometer, which separates electrons according to their energy to obtain information about the identity, bonding and electronic structure of atoms within the specimen. A CCD TV camera records electron shadow maps, or Ronchigrams [1], of amorphous areas for measurement of aberration parameters. A photo of the column is shown at the right. It is enclosed in a magnetically and acoustically shielded room, and supported by vibration isolation mounts. The original oil diffusion pumping system has been replaced with a large ion pump. This instrument is unusual in having high voltage connections [2, 3] at both the top and bottom of the machine to allow EELS spectroscopy with very high accuracy and resolution. Also in this machine the gun chamber has been modified to allow insertion of a monochromator [4] which will improve the EELS resolution to 60 meV or better.

[1] V. Ronchi, Forty years of history of a grating interferometer, Applied Optics 3, 437-450 (1964).

[2] P.E. Batson, High Resolution Electron Energy Loss Spectrometer for the Scanning Transmission Electron Microscope, Rev. Sci. Inst. 57, 43-48 (1986).

[3] P.E. Batson, Parallel Detection for High Resolution Electron Energy Loss Studies in the Scanning Transmission Electron Microscope, Rev. Sci. Inst. 59, 1132-1138 (1988).

[4] H.W. Mook, P.E. Batson, and P. Kruit, Monochromator for high brightness electron guns, in 12th European congress on electron microscopy, Vol. III, (2000) pp. 315 -316. 

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