Mapping
the
electronic
properties
of
individual
graphene
grain boundaries
This false color tunneling conductivity map shows the electronic
structure of a graphene grain boundary. The two graphene grains (left
and right regions) are separated by a linear grain boundary (middle
region). The conductivity of the grain boundary is much lower. Graphene
grain boundaries can form p-n-p junctions with sharp interfaces of the
nm scale.
Publications
>> |
Revealing
the
grain
structure
of
graphene
This false color AFM image shows the surface of graphene grown by
chemical
vapor deposition. The colors show the orientation of the grains
determined by atomic
scale images. Publications
>> |
Color
based
discrimination
of
chitin-air
nanocomposites
in
butterfly
scales
 Dorsal side perpendicular view photographs of nine
investigated
Polyommatus species.
The spectral signatures of the nine species analyzed using an
artificial neural network software
show that despite the fact that all possess similar nanostructure, the
spectral
signatures exhibit enough characteristic differences to allow
the unambiguous identification of conspecific individuals.
Spectral measurements can be used as a fast
and cheap way of checking the relationships of butterfly
species in a group having common ancestry
Publications
>> |
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.
Publications
>> |
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.
Publications
>>
Supplementary
Material
>> |
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
>> |
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
>> |
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)
>> Publications
>> |
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) >> Publications
>> |
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).
Publications
>> |
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.
Publications
>> |
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).
Publications
>> |
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.
Publications
>> |
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
>> |
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).
Publications
>> |
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
>> Publications
>> |
BioPhot
Symposium
2005
 "Complexity and
evolution of photonic
nanostructures in bioorganism: templates for material sciences", 23.
Sept. 2005, Budapest
Details
>> |
Hungarian
Nanotechnology
Symposium
2005
 HUNS-2005
(MANS-2005)
is
a
national
"Mobilization
Workshop"
organized
within
the
framework
of
EU
FP6
NENAMAT
project.
Details
>> |
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.
Publications
>> |
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
>> Publications
>> |
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
>> Publications
>> |
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.
Publications
>> |
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.
Publications
>> |
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
>> |
|
Dynamical
analysis of the STM tip -- graphene tunneling event
 This pair of images shows two situations: when
the electron is tunneling from the tip of a Scanning Tunneling
Microscope into a bulk sample (left)
and when it is tunneling into a thin layer (right), like graphene. In the
case of the bulk sample the direction of the momentum of the electron (red arrow) does not change, but
for the thin layer the momentum (blue
arrow) has to change direction. We analyzed this phenomenon, together
with other important effects influencing the STM imaging mechanism of
graphene.
Publications
>> |
Anisotropic
dynamics
of
charge
carriers in graphene
 |
|
This animation (click
to
enlarge) shows the
time evolution of an electron wave packet on the graphene surface. The
wave packet is inserted from a simulated Scanning Tunneling Microscope
tip (see the left image, a vertical cross section). The right image
(horizontal cross section) shows a peculiar anisotropic dynamics, which
may have important applications in future graphene nanodevices.
|
Publications
>> |
Parallel
nanolitography
 This
STM image shows two graphene nanoribbons etched by a double tip
with two apexes situated about
31 nm apart from each other.
Parallel processing is of utmost importance if practically relevant
nanocircuitry from graphene is targeted.
We examined parallel processing of graphene by scanning tunneling
lithography (STL) and
by carbothermal etching (CTE).
Publications
>> |
Energy
resolved tunneling conductance mapping of
functionalized carbon nanotubes
 The
upper image is a schematic illustration of our novel CNT immobilization
technique, which facilitates the study the topography and electronic
structure of functionalized
CNTs by STM.
The technique is based on incorporating the functionalized multiwalled
CNTs into
a few-layer graphene-nanotube composite, as shown on the lower STM
image.
Our measurements illustrate the advantage energy resolved tunneling
conductance maps can give,
namely to spot sample features that are not apparent from STM
topography maps and to provide
information on local functionalization and doping.
Publications
>> |
Photonic
nanoarchitectures
in
butterflies
and
beetles
--
a
review
Nature
began developing photonic nanoarchitectures millions of years before
humankind. In their review paper, L. P. Biró
and J.-P.
Vigneron, present a survey of the development of natural photonic
crystal-type nanoarchitectures occurring in butterflies and beetles
from the standpoint of physics and materials science The
characterization, modeling methods, and rapidly growing number of
bioinspired or biomimetic applications are discussed.
Publications
>> |
Raman
scattering on graphene zigzag edges
 |
|
Theory has predicted rich and very distinct
physics for graphene nanodevices with boundaries that follow either the
armchair or the zigzag crystallographic directions. We have
demonstrated that hexagonal holes obtained by anisotropic etching of
graphene are bounded predominantly by zigzag edges which do not
contribute to the D peak in Raman spectroscopy.
|
Publications
>> |
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
>> Publications
>> |
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.
Publications
>> |
Effect
of disorder on the color of photonic crystals
 |
| 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. |
Publications
>> |
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.
Publications
>> |
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
>> Publications
>> |
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.
Publications
>> |
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.
Publications
>> |
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.
Publications
>> |
Transport
through
a
graphene
nanoribbon
 |
| 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. |
Publications
>> |
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
>> |
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.
Publications
>> |
BioPhot
Symposium
2007
"Complexity and
evolution of photonic
nanostructures in bioorganism: templates for material sciences", 24-25.
Sept. 2007, Budapest
Details
>> |
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.
Publications
>> |
Manhattan plot
 |
| 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. |
Details
>> Publications
>> |
Structural
models
for
coiled
nanotubes
 |
| 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. |
Publications
>> |
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
>> |
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
>> |
|
