by Merijn Pen | Jul 10, 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.
by Merijn Pen | Jul 10, 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 | Jul 10, 2017
Drs. Kuang He
Department of Materials, University of Oxford Authors | Kuang He, Alex W. Robertson, Ye Fan, Christopher S. Allen, Yung-Chang Lin, Kazu Suenaga, Angus I. Kirkland and Jamie H. Warner. Email | jamie.warner@materials.ox.ac.uk
| Application |
Temperature Dependence of the Reconstruction of Zigzag Edges in Graphene |
| Authors |
Kuang He, Alex W. Robertson, Ye Fan, Christopher S. Allen, Yung-Chang Lin, Kazu Suenaga, Angus I. Kirkland and Jamie H. Warner. |
| Journal |
ACS Nano, 2015 |
| Publication |
Full Publication Here – DOI: 10.1021/acsnano.5b01130 |
Temperature Dependence of the Reconstruction of Zigzag Edges in Graphene
ABSTRACT: We examine the temperature dependence of graphene edge terminations at the atomic scale using an in situ heating holder within an aberration-corrected transmission electron microscope. The relative ratios of armchair, zigzag, and reconstructed zigzag edges from over 350 frames at each temperature are measured. Below 400 C, the edges are dominated by zigzag terminations, but above 600 C, this changes dramatically, with edges dominated by armchair and reconstructed zigzag edges.
We show that at low temperature chemical etching effects dominate and cause deviation to the thermodynamics of the system. At high temperatures (600 and 800 C), adsorbates are evaporated from the surface of graphene and chemical etching effects are significantly reduced, enabling the thermodynamic distribution of edge types to be observed. The growth rate of holes at high temperature is also shown to be slower than at room temperature, indicative of the reduced chemical etching process. These results provide important insights into hthe role of chemical etching effects in the hole formation, edge sputtering, and edge reconstruction in graphene.
Figure above: Edge behavior at room temperature (∼25 C). (ac) Three typical HRTEM images of graphene holes at that temperature. The edges are color-coded to differentiate the types of edge configurations. Red represents armchair; yellow is zigzag, and green is Rec. 57; white indicatesmixed or unidentified edge types. The inset in (a) and (b) shows typical long-ordered zigzag and armchair configurations at this temperature. The statistics for three examples are shown in (d); the percentages of edges occupied by different types of edges are ranked accordingly: black columns represent panel (a), red columns panel (b), and blue columns panel (c). (e,f) Long-ordered zigzag edge from both bulk of graphene and edge of a nanoribbon, respectively. (g) Representative long-ordered armchair edge found at this temperature. The o iginal image ofwhich (eg) are cropped fromthose shown in Figure S1ac of Supporting Information. All scale bars are 1 nm.
by Merijn Pen | Jul 10, 2017
