Nanopatterning of graphene with crystallographic orientation control
Computed STM image of a graphene nanoribbon with imperfect edges.
Note the localized electronic states on the edges.
This shows the paramount importance of edge structure on the
electronic properties of graphene nanodevices.
Our recent review paper written by L. P. Biró and Ph. Lambin gives an up-to-date survey of methods capable of cutting graphene with precise edge control.
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Crystallographically selective nanopatterning of graphene
on SiO2
Hexagonal holes of 380 nm diameter etched into graphene layer on an insulating surface.
Our new carbothermal etching process makes it possible to produce graphene
nanoribbons and Y-junctions with zigzag or armchair edges.
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Supplementary Material >>
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Colorful beetle as a model In nanoarchitecture research
During a lecture Professor Biró gave in Taiwan, he was shown three identical-looking beetles, but with different colors. Several months later, we revealed a novel intercalated photonic nanoarchitecture composed of a regular multilayer and nanorods perpendicular to the layers in the elytra of this Taiwanese beetle (Trigonophorus rothschilid varians). We succeeded in producing artificial bioinspired nanoarchitectures, with behaviors very similar to that of the living model, by nanomachining. Our results were published in the journal Interface of the Royal Society, and also displayed on the websites of BBC News and Hungarian Academy of
Sciences.
Interface paper >>
News on HAS homepage >>
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Biological and bioinspired photonic nanoarchitectures (a video talk)
Photonic nanostructures exhibit a broad range of optical phenomena: coloration, iridescence, photonic band gap, polarization, diffraction, total reflection, fluorescence, etc. These materials have many existing and potential applications in technology, e.g. in communication, signal processing, computing, and as ecological freindly colorants. But biological evolution created photonic nanoarchitectures in living organisms more than 500 Million years ago. This video presentation prepared for Hungarian Physics Students gives and account of our research in this field.
Deltails >>
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Role of defects in chemical sensing properties of carbon nanotube films
As the outer wall of the carbon nanotube plays a dominant role in the electrical transport along the axis, the influence of the ambient on its electrical properties offers the possibility of chemical sensing.
In our work, the modification of electrical conduction was used as the detection principle in random networks of carbon nanotubes.
A sensor made of arc-grown SWCNTs and two others made of arc-grown MWCNTs were also investigated.
The response of 24 different sensors to 10 vapors was studied.
AVI movie (5 M) >>
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Measuring the thickness of graphene layers by TAFM
An Atomic Force Microscope in its "tapping mode" (TAFM) sweeps the sample surface by an oscillating probe attached to a cantilever.
This animation shows how does the oscillation change at a step edge and also when the material of the surface is changed below the probe tip.
We determined what TAFM imaging parameters are necessary to measure the thickness of thin (< 1 nm) FLG (Few Layer Graphene)
layers correctly.
AVI movie (2 M) >>
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Tailor-made graphene nanoribbons
Results of the Nanostructure Department of the Research Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences were selected as cover page illustration for the July issue of Nature Nanotechnology (IF: 14.9). According to the Editor, the special importance of the achievements of Tapasztó et al. is that they propose solutions for two major challenges of nanoelectronic circuit manufacturing: the engineered, precise cutting of nanometer size circuit elements and their controlled connecting. A nano-knee ribbon is shown on the cover page of Nature Nanotechnology, two grapheme nanoribbons of only 8 nanometers in width connected with each other under an angle of 30 degreed (the region between the thick red lines).
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Bioinspired photonic crystals
Top view Scanning Electron Microscope image of a multilayer structure made from SiO layers and 50 nm Indium spheres (the multilayer was broken to reveal the internal layers). This structure succesfully reproduces the optical properties of Albulina Metallica butterfly wing scales.
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Making of graphene layers from oxidation of graphite plates
These 3x3 um Atomic Force Microscopy images show the effect of thermal oxidation on a few-layer graphite platelet (a). We showed that such platelets can be thinned by thermal oxidation in air, and individual graphene layers can be formed (b).
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Switchable biological mirror of the tortoise beetle
The tortoise beetle Charidotella egregia is able to modify the structural color of its cuticle reversibly, when disturbed by stressful external events. The gold coloration displayed by animals at rest arises from a chirped multilayer reflector maintained in a perfect coherent state by the presence of special body liquid in the porous patches within each layer, while the red color displayed by disturbed animals results from the destruction of this reflector by the expulsion of the liquid from the porous patches, turning the multilayer into a translucent slab that leaves an unobstructed view of the deeper-lying, pigmented red substrate.
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Photonic single- and polycrystal structures on butterfly wings
This image shows the dorsal (a) and ventral (b) surface of the Cyanophrys remus butterfly together with the ventral surface of an old, bleached exemplar (c).
With a detailed experimental and theoretical study we showed that while the bright metallic blue dorsal color is caused by photonic single crystal scales, the matt green ventral color is the result of a photonic polycrystal structure. The bleached color (c) is caused by the decay of the absorbing pigment with time.
Publications >>
New Scientist >>
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Carbon nanotube defects imaged by STM
15x15 nm atomic resolution STM image of a multi-wall carbon nanotube (MWCNT)
showing individual atomic-scale defects caused by Ar ion irradiation.
The defects appear as hillocks which is due to the
increased tunneling current at the defect sites.
Electronic superstructures can be observed in the vicinity of the
defect sites with the period larger than the period of the atomic
structure. (Shown by green lines.)
The superstructures appear due to the redistribution of the
local density of states (LDOS).
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Spray pyrolysis production of CNTs
This 10 um SEM image shows carbon nanotubes produced by the spray pyrolysis method.
This method is based on the simultaneous injection of a metallocene-hydrocarbon solution through a sprayer into the reaction furnace. Major advantage of is the direct and continuous generation of fresh catalytic particles throughout the entire growth cycle. This gives the possibility to scale up the method for continuous or semicontinuous production of carbon nanotubes at commercially viable prices.
Details >>
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BioPhot Symposium 2005
"Complexity and evolution of photonic nanostructures in bioorganism: templates for material sciences", 23. Sept. 2005, Budapest
Details >>
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Hungarian Nanotechnology Symposium 2005
HUNS-2005 (MANS-2005) is a national "Mobilization Workshop" organized within the framework of EU FP6 NENAMAT project.
Details >>
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Photonic crystals in plants
This SEM image shows the filaments covering the leaflets surrounding
Edelweiss (see inset) bracts.
The fine structure of the filaments is a photonic crystal structure,
one of the few examples of photonic structure found in a plant.
Calculations support the idea that this wooly layer absorbs near-UV light
before it reaches the cellular tissue.
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Wing scale nanostructure in butterflies
Our studies of buttefly wing scale micro- and nanostructure by electron microscopy
show that structural color manipulation is a general instrument in the evolution
of butterflies.
Our study has revealed a deep interwining between physics and biology.
Details >>
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Biological photonic crystals
This animation shows the variation of the iridescent color
of a butterfly as the angle of incident light is changed.
This phenomenon is caused by the photonic crystal microstructure
of the wing scales.
We measure the optical and thermal properties of the wings
and study their microstructure by SEM and TEM.
Details >>
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Coiled nanotubes
A coiled single wall carbon nanotube is shown on this
STM image. There are certain catalyst and reaction conditions,
which enhance the formation of regularly coiled structures.
This may have to do with the formation ratio and the annealing
out of pentagon (5) and heptagon (7) rings as compared
to hexagons (6). This ratio can be influenced by the proper
combination of growth conditions, The annealing out of
5, 7 rings may be avoided by the using of the low reaction
temperatures typical for the CVD process, while the high
temperatures used in the arc growth anneal out the 5,
7 rings.
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Y-connections
An Y-connection of single wall carbon nanotubes is shown
on this STM image. Our group was the first to observe
SWNT Y-connections predicted earlier theoretically.
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Continuous nanotube production in underwater arc
Multi-wall carbon nanotubes are produced by generating
an AC electric arc between two identical carbon rods,
submerged in deionized water.
Details >> Publications >>
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Web-Schrödinger 2.1
 Web-Schrödinger is a program for the interactive solution of the time dependent two dimensional (2D) Schrödinger equation. The program itself runs on our server and can be used through the Internet with a simple Web browser. Several example configurations are provided with version 2.1. The user can save and load own configurations.
Details >>
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Graphene by HOPG fluorination and water vapor reduction
STM image (size 3 nm) of the surface of fluorinated graphite in ambient air.
Graphite fluoride was obtained by fluorination of highly oriented pyrolytic graphite (HOPG) by a gaseous mixture of BrF3 and Br2.
XRD, STM, AFM, Raman spectroscopy and XPS were used to investigate the fluorination process and the reduction of CF2 to graphene
on interaction with water vapor.
It was found that the crystallinity of the topmost graphene layer produced by reduction is superior as compared to oxidation exfoliated graphene.
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Effect of disorder on the color of photonic crystals
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This animation shows how the Fourier power spectrum of a perfect crystal is changing, when the lattice planes are randomly shifted.
Understanding the effect of randomness on the Fourier image helped us to explain, how the Albulina metallica butterfly creates its viewing angle dependent coloration by a disordered nanostructure. |
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Tuning the electronic structure of graphene by ion irradiation
We irradiated single atomic layer graphene sheets with Ar+ ions in order to study the effect of defects and disorder on the electronic structure.
The samples were investigated by STM and STS.
The most important consequence of the induced disorder is the reduction in the Fermi velocity, as illustrated in this figure.
Hence we can tune the Fermi velocity of graphene by ion irradiation,
which could open up new perspectives for graphene electronics.
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Nano Christmas
 Wish You Merry Chrsitmas with this nano Christmas tree calculated by Web-Schrödinger. It shows the scattering of a wave packet on a potential forming an X-mas tree. The height of the tree is 3 nm. See the "File / Load Example" menu of the program!
Details >>
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Photonic nanoarchitectures in butterfly scales as gas sensors
From 20 examined butterfly species all showed selective gas/vapor sensing when
various volatile organic compounds were introduced as additives in ambient air.
Each butterfly species gives characteristic response both for species, i.e., for its typical nanoarchitecture,
and for the seven test vapors used. Fast response time, reproducible and concentration dependent signals are demonstrated.
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Diffraction and fluorescence in the iridescence of Troides magellanus
This birdwing butterfly lives in a restricted area of the Philippines.
The yellow-green color of its hindwings is caused by a pigment, but as shown on the animation,
when viewed at a specific angle, the hindwing shows a bright blue flash.
The bright blue color is concentrated at a narrow angular range, this ensures that it is seen only
by potential mates, but unseen by the predators.
Detailed analysis showed that this effect is caused by a blazed optical grating on the surface of the wing scales.
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Interference of electronic waves on the graphite surface
58 x 58 nm atomic resolution STM image of the graphite surface near the vicinity of a defect site created by ion irradiation.
Position dependent superstructure patterns are present near the defect, as marked by the two circles.
Our results indicate that superstructure patterns are mainly determined by the available scattered states of the system rather
than the detailed structure of the defect site.
We propose an interference model, which can explain the presence of coexisting
superstructures both on graphite and carbon nanotubes.
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Transport through a graphene nanoribbon
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This animation of 6 fs duration shows the transport of an electronic wave packet through a graphene nanoribbon. Pronounced edge states are seen and the interference of the eigenstates of the nanoribbon causes different patterns to appear along the CC bonds.
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BioPhot software & database
 BioPhot Analyzer is a program for organized storage and retrieval of images (photographic and microscopic) and measurements of butterfly wing scales. Butterfly specific image- and data analysis tools help the user to understand the raw data. The software was developed by a SME, Softadmin.
Details >>
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Imaging electron interference patterns on MWNTs
This animation shows the changing of the calculated STM image of a
multi-wall carbon nanotube (MWNT) as a function of the Utip
voltage applied to the STM tip.
Our new interference model accounts for the complex electron density oscillations
near defect sites.
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BioPhot Symposium 2007
"Complexity and evolution of photonic nanostructures in bioorganism: templates for material sciences", 24-25. Sept. 2007, Budapest
Details >>
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Energetics of CNT bundles
This graph shows the interaction potential curve of two aligned (10,10) carbon nanotubes with one tube fixed and the other rotating about its axis. We studied in detail the energetics of CNT pairs and bundles of CNTs.
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Manhattan plot
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The statistical distribution of a large number of helically coiled carbon nanotubes was analyzed in a cross-correlated way in their
geometrical configuration space defined by diameter and pitch. Stability islands were identified, in which the number of coils exceeds
about 15-10 times the value corresponding to a uniform distribution.
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Details >>
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Structural models for coiled nanotubes
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By assembling azulene units (fused pentagon-heptagon pairs) and hexagons,
and applying specific wrapping rules to these structures resembling
some recently-proposed Haeckelite structures
(Terrones et al., Phys. Rev. Lett. 84, 1716 (2000)),
a large variety of toroidal, coiled, screwlike, and double-helix
structurescan be generated.
In these structures the ratio of nonhexagonal ringsto hexagonal units
varies from 4:1 to 4:3 by contrast to earlier coilmodels
where this ratio was well below unity.
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3D calculation of tunneling through a SWNT in STM
This is a snapshot from the quantum mechanical time dependent
simulation of the tunneling of an electron wave packet
through a model of a nanotube in an STM setup.
Details >>
Publications >>
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2D tunneling calculations through SWNTs in STM
This animation shows the time development of an electron wave packet while tunneling
through a model of a nanotube in an STM setup.
Details >>
Publications >>
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