Room-temperature
giant current density
discovered in Koops-GranMat
Darmstadt Art Nouveau Center Mathildenhöhe
Hans W.P. Koops
Hiroshi Fukuda
HaWilKo GmbH
64372 Ober-Ramstadt, Germany
[email protected]
Hitachi High Technologies
Tokyo, 105-8717 Japan
FEBIP – Focused Electron Beam Induced Processing
Tokyo Sky Tree
• Focused electron beam induced deposition (FEBID) to fabricate
3D-nano structures
A slow technology for etching and deposition of materials
The required dose for etching is :
De > 5mA/cm²
The required dose for deposition is :
Dd > 100 mA/cm²
Primary electrons and a ca. 4 times higher number of secondary
electrons destroy the precursor molecules and form with the sample
material new volatile compounds : etching.
Deposition forms from precursor molecules new crystalline and
amorphous compounds. Koops GranMat describes a material
composed from metal crystals embedded in an insulating matrix.
The new nanogranular material is built in an epitaxial growth process
with two phases having different condensation temperatures,
and using an electron beam of high dose and slow motion
( > 1 msec per pixel step)
TEM (30 – 200kV)
SEM (1 – 30 kV)
1 pA – 10 nA, 2 nm spot
Power density: 60 MW/cm²
H. W. P. Koops, et al., JVST B6 477 (1988)
Bohr‘s stability conditions for Eigenstates employed to orbitals
at the crystal surface have a level splitting much smaller than
the bandgap in semiconductors(Hypothesis H.W.P. Koops 2009)
In Koops-GranMat one nano-crystal is composed from ca.1000 atoms in a single crystal
form. The crystal is embedded in a Fullerene matrix which is also geometry quantized.
Electrons can form the electron gas in the crystal surface orbital modes.
Wavelength of electrons at Fermi level is ~ 2 nm (Pt/C)
Bohrs Eigenvalue in circular states at the crystal rim :
Surface Orbital (n ), n= 3 at 2 nm diameter crystals
Bohr‘s Eigenvalue transmission states( m /2)
NGM – show photo - sensitivity
NGM – have a negative resistivity
with temperature
0.5
0.4
0.3
)
A
n
(
I 0.2
0.1
0
0
2
4
6
8
U (mV)
1.5
Surface Orbital state n=5
distance to crystal surface 0.53 nm
Surface Orbital state n=4
Surface Orbital state n=3
128 mV
75 mV
(] K. Murakami, F. Wakaya, M. Takai, J. Vac. Sci. Technol. B, vol. 25, no. 4,
0
0
WAActivation energy for Variable Range Hopping
at 300 K : Pt/C: 128 meV Au/C: 75 meV
(1) Negative temperature dependence of resistivity
(2) Photocurrent response – 3 x more efficient at 700 nm than Si solar cell in white
(3) High current carrying capacity (>10 MA/cm2 current density),
(4) High contact resistance due to hopping tunnelling (< 0.01 Ohmcm)
(5) No heat damage (despite (3) and (4)),
(6) Low emission voltage.
> 1 GA/cm²
(7) Coherent electron emission from field emitter tip
>10 MA/cm2
pp. 1310-1314, 2007)
It is a contradiction , that 250 kA/cm²
Gold: resistance. 1 µOhmcm,
and NGM: Contact resistance 0.01 Ohm cm
Carries Current: 250 kA/cm²
respectively 50 MA/cm² on 70 nm dia. wire
The high current density in NGM can be supplied by Gold only via a large area contact
from Gold to NGM , which must be provided, like for Superconductors to Metal
The classical BEC happens at super low temperatures (< milli-Kelvin)
Extract from Wikipedia.
Cornell and Weiman created a BEC ( Bose-Einstein Condensate) with rubidium (Rb)atoms.
At zero Kelvin all molecular motion stops. All the atoms have exactly the same levels, like twins.
The result of this clumping is the BEC. The group of rubidium atoms sits in the same place,
creating a "super atom." There are no longer thousands of separate atoms.
All their highest orbitals overlap in the condensate , that gives the condition that electron and
holes can form Bosons and all occupy the same level. Their motion becomes coherent .
Investigating field electron emission from such materials Takai and Murakami in 2008
found a coherent emission from several sites , indicated by Young’s interference patterns
Fig: a: Pt/C deposit , b: Tip after RIE etching, right: fringe-like electron-emission pattern observed in
field emission from a Pt field emitter fabricated by electron -beam-induced deposition.
K. Murakami, F. Wakaya, and M. Takai, “Observation of fringelike electron -emission pattern in field emission from Pt
field emitter fabricated by electron-beam-induced deposition,” J. Vac. Sci. Technol. B, vol. 25, no. 4, pp. 1310 -1314, 2007
n Indirect exciton clusters packed in 2–4 nm-diameter metal
nano-particles are produced by FEBIP from organometallic
precursors by slow step deposition
n Using Bohr’s Atom model overlapping surface orbital eigenstates were found which overlap to similar states of
neighbouring crystals and allow a Boson-condensate
n A predicted high carrier density suggests electron-hole liquid
n Possible charge transport mechanisms range from an
artificial semiconductor-like mechanism to indirect exciton
annihilation in an e-h BCS condensate
n The Bose-Hubbard phase diagram suggests a possible
platform for excitonic quantum condensate
n Electrical resistance measurements show no line resistance
but a contact resistance which depends on the contact area
Acknowlegdments
The authors acknowledge the contributions by theoretical, experimental
and machine time support of Raith GmbH , TU Ilmenau, IMP Tu Darmstadt,
Tu Wroclaw , PL, Hitachi High Technologies, Japan, as well as support by
discussions with
Prof. Hans. L. Hartnagel from TU Darmstadt, Dr. Hirojuki Ito from HHT, Dr.
Ulrich Koops, and Dr. Josef Sellmair, from Sellmair Nano-Electrotechnics.
Hans W.P. Koops & Hiroshi Fukuda, IVNC 2014
Pt/C
0.5
Crystal surface
Nanocrystal Pt/C 2nm or Au/C 4 nm diameter, separation 1 nm
Significant features of NGM
)
A1
m
(
I
50
U (V)
100
F. Floreani 2000
Koops et al. Conductive dots, wires, and supertips
JVSTB 14 6 1996 4105