by Merijn Pen | Apr 13, 2017
Dr. Chris B. Boothroyd
Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Germany Authors | C.B. Boothroyda, M.S. Morenob, M. Duchampa, A. Kovácsa, N. Mongec, G.M. Moralesc, C.A. Barberoc, R.E. Dunin-Borkowskia Email | c.boothroyd@fz-juelich.de
| Application |
Atomic Resolution Imaging and Spectroscopy of Barium Atoms and Functional Groups on Graphene Oxide |
| Authors |
C.B. Boothroyda, M.S. Morenob, M. Duchampa, A. Kovácsa, N. Mongec, G.M. Moralesc, C.A. Barberoc, R.E. Dunin-Borkowskia |
| Journal |
Ultramicroscopy Journal, 2014 |
| Sample |
Graphene |
| Topic |
Contamination Free, 2D Materials, Soft Matter, E-Beam Sensitive Imaging |
| Techniques |
HRTEM, HRSTEM, EELS, Diffraction |
| Keywords |
Graphene oxide; Functional groups; Scanning transmission electron microscopy; Transmission electron microscopy; Spectrum imaging; Atomic resolution; Single atom imaging |
| Publication / D.O.I. |
Full Publication Here |
Atomic Resolution Imaging and Spectroscopy of Barium Atoms and Functional Groups on Graphene Oxide
ABSTRACT: We present an atomic resolution transmission electron microscopy(TEM) and scanning TEM(STEM) study of the local structure and composition of graphene oxide modified with Ba2+. In our experiments, which are carried out at 80kV,the acquisition of contamination-free high-resolution STEM images is only possible while heating the sample above 400C using a highly stable heating holder. Ba atoms are identified spectroscopically in electron energy-loss spectrum images taken at 800C and are associated with bright contrast in high-angle annular dark-field STEM images. The spectrum images also show that Ca and O occur together and that Ba is not associated with a significant concentration of O. The electron dose used for spectrum imaging results in beam damage to the specimen, even at elevated temperature. It is also possible to identify Ba atoms in high-resolution TEM images acquired using shorter exposure times at room temperature, thereby allowing the structure of graphene oxide to be studied using complementary TEM and STEM techniques over a wide range of temperatures.
FIGURE ABOVE: HAADF STEM images acquired at a specimen temperature of 800 C (a) before and (b) after recording the spectrum image (the total time of spectrum imaging is 800s). The area of spectrum imaging is marked by the box. While the area surrounding the box is relatively unchanged after acquiring the spectrum image (except for a small drift and local distortion), the area from which the spectrum image was acquired has changed significantly.
FIGURE ABOVE: Color images created from a selection of the spectrum images which were acquired from graphene oxide with Ba imaged at a temperature of 800 C by using STEM spectrum imaging method. The images show the spatial relationships between the elements, corresponding to the following colours: (a) Ba red and C cyan; (b) O red and C cyan; (c) Ca red and C cyan; (d) Ba red, Ca green and C blue. The spectrum image shows that Ba, O and Ca are present mostly in the areas where the C is thinnest and that Ca and O have very similar distributions.
DENSsolutions Comments:
Graphene, graphene-like two dimensional and other soft-mater materials attract increasing research efforts. Characterization of these type of materials in TEM, however, suffers contamination problems and e-beam damage.
Contamination, referring to the build-up of decomposed carbon on a specimen, heavily influences the quality of electron microscopy imaging. Graphene and graphene-like two dimensional materials suffer contamination the most because of two reasons 1. these materials are ultrathin, with low image contrast, the build up contamination contrast blur the original contrast easily; 2. these materials are with large surface area, easier to absorb hydrocarbon, water to form contamination under e-beam.
DENSsolutions heating system provides the opportunity to image these samples free of contamination at elevated temperature, without sacrificing the quality/resolution of imaging. The extreme high stability of DENSsolutions heating system (sample spatial drift less than 0.5nm/min) can even allow the researchers using a long exposure time (5s-8s) to image the individual carbon atoms for improving the contrast. Furthermore, the low drift allows chemical sensitive spectrum imaging to be carried down to atomic level.
by Merijn Pen | Apr 13, 2017
Dr. Amanda S. Barnard
CSIRO Materials Science & Engineering, Australia Authors | Amanda S. Barnard, Neil P. Young, Angus I. Kirkland, Marijn A. van Huis and Huifang Xu. Email | Amanda.Barnard@csiro.au
| Application |
Nanogold – A Qualitative Phase Map (cited 86 times) |
| Authors |
Amanda S. Barnard, Neil P. Young, Angus I. Kirkland, Marijn A. van Huis and Huifang Xu. |
| Journal |
ACS Nano, 2009, 3 (6), pp 1431–1436 |
| Sample |
Nanoparticles |
| Topic |
Catalyst Stability, Phase Transformation |
| Techniques |
HRTEM |
| Keywords |
Gold; Nanoparticles; Shape; Phase diagram; Thermodynamics; Modeling |
| Publication / D.O.I. |
Full publication here DOI: 10.1021/nn900220k |
Nanogold – A Qualitative Phase Map
ABSTRACT: The development of the next generation of nanotechnologies requires precise control of the size, shape, and structure of individual components in a variety of chemical and engineering environments. This includes synthesis, storage, operational environments and, since these products will ultimately be discarded, their interaction with natural ecosystems.
Much of the important information that determines these properties is contained within nanoscale phase diagrams, but quantitative phase maps that include surface effects and critical diameter (along with temperature and pressure) remain elusive. Here we present the first quantitative equilibrium phase map for gold nanoparticles together with experimental verification, based on relativistic ab initio thermodynamics and in situ high-resolution electron microscopy at elevated temperatures.
Figure: “Until recently growing gold nanoparticles was a little like a box of chocolates – you never know what you were going to get!”
DENSsolutions Comments
Nanoparticles of gold are currently attracting considerable attention for use in biomedical applications including drug delivering, heating, sensing and in nanocatalysis. However, our ability to control the properties upon which these applications are based is still intrinsically linked to the nanomorphology of individual particles.
Most theoretical models predict that, in general, the more perfect the nanoparticles, the better they perform. However, real nanoparticles are rarely crystallographically ideal, and planar defects such as contact twins and intrinsic or extrinsic stacking faults, form during growth in materials with low stacking fault or twin boundary energy, and surface energy anisotropy. Gold features in this group, often exhibiting structural and morphological modifications including single or multiple (parallel, contact) twinning and cyclic twinning resulting in decahedral and truncated decahedral structures. Verifying a phase map given by theoretical simulation is very challenging undertaking, which requires mapping gold particles at various elevated temperatures.
The researchers using a range of DENSsolutions heating systems were able to observe gold particles at various elevated temperature. The extreme low drift at elevated temperature allows structural and shape transformations in individual gold particles that could be imaged with atomic resolution. By using approach, the researchers succeed in mapping the gold phase diagram experimentally.
by Merijn Pen | Apr 12, 2017
Dr. Qiang Xu
Kavli Institute of Nanoscience, Delft University of Technology,The Netherlands Authors | Qiang Xu, Meng-Yue Wu, Grégory F. Schneider, Lothar Houben, Sairam K. Malladi, Cees Dekker, Emrah Yucelen, Rafal E. Dunin-Borkowski and Henny W. Zandbergen. Email | h.w.zandbergen@tudelft.nl
| Application |
Controllable Atomic Scale Patterning of Freestanding Monolayer Graphene at Elevated Temperature |
| Authors |
Qiang Xu, Meng-Yue Wu, Grégory F. Schneider, Lothar Houben, Sairam K. Malladi, Cees Dekker, Emrah Yucelen, Rafal E. Dunin-Borkowski and Henny W. Zandbergen. |
| Journal |
ACS Nano, 2013, 7 (2), pp 1566–1572 |
| Sample |
Graphene |
| Topic |
Contamination Free, 2D Materials, Soft Matter, E-Beam Sensitive Imaging |
| Field |
Material Science, Chemistry, Electronics, Life Science |
| Techniques |
HRTEM, HRSTEM, EELS, Diffraction |
| Keywords |
Graphene; Controlled Sculpting; Nondestructive Imaging; Nanopatterning; Self-repair |
| Publication / D.O.I. |
Full Publication Here – DOI: 10.1021/nn3053582 |
Controllable Atomic Scale Patterning of Freestanding Monolayer Graphene at Elevated Temperature
ABSTRACT: In order to harvest the many promising properties of graphene in (electronic) applications, a technique is required to cut, shape, or sculpt the material on the nanoscale without inducing damage to its atomic structure, as this drastically influences the electronic properties of the nanostructure. Here, we reveal a temperature-dependent self-repair mechanism that allows near-damage-free atomic-scale sculpting of graphene using a focused electron beam. We demonstrate that by sculpting at temperatures above 600 C, an intrinsic self-repair mechanism keeps the graphene in a single-crystalline state during cutting, even though the electron beam induces considerable damage. Self-repair is mediated by mobile carbon ad-atoms that constantly repair the defects caused by the electron beam. Our technique allows reproducible fabrication and simultaneous imaging of single-crystalline free-standing nanoribbons, nanotubes, nanopores, and single carbon chains.
FIGURE ABOVE: Annular dark field STEM images of graphene ribbon arrays sculpted in a reproducible way by using a script-controlled electron beam at elevated temperature. After the first sculpting process, the patterns were imaged as shown in (a). Next, each ribbon was reduced in width precisely, and image (b) was acquired. Intensity line profiles across the ribbon outlined by the white frames in (a) and (b) are shown in (c) and (d), respectively. The width of the ribbon is estimated to be 4.0 nm after initial sculpting and 1.9 nm after final sculpting.
DENSsolutions Comments
Objective & Goal
Graphene, carbon nanotube and other soft-mater materials suffers irradiation damage caused by high energy electron beam during TEM characterization. The e-beam damage limits the observation time or observation electron beam condition, thus requiring a way to prevent. Moreover, application of graphene needs to patterning graphene into various functional devices with nano-size geometry. The e-beam induced damage can be utilized for creating a lithography method for graphene patterning. Achieving control of e-beam damage of graphene becomes an essential topic.
Benefit
DENSsolutions heating system provides the extreme high stability of sample at elevated temperature (sample spatial drift less than 0.5nm/min) At the elevated temperature, the e-beam induced defects of the sample can be repaired with a corresponding speed, therefore, provides an extra parameter for control of e-beam damage.
