Transcript Слайд 1 - Science and Technology Center in Ukraine

National Scientific Centre
“Kharkov Institute of
Physics and Technology”,
Kharkov, Ukraine
High-field technology for processing
of nano-sized objects
Vjachslav Ksenofontov
PhD
senior researcher
[email protected]
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Developed technology for nanoscaled objects provides for surface
modification into atomically smooth
state.
Applications:
- ultra-sharp atraumatic microsurgical
instruments;
- ultra-fine microprobes for scanning
tunneling microscopes;
- field emitters with localized emission.
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• The technology is based on the
discovered phenomenon of field
evaporation of metals in dielectric
liquids and gas stimulated field
evaporation.
• Previous method of field evaporation in
high vacuum, faced problem caused
by the destruction of objects under
mechanical stress generated by superhigh electric field.
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SMOOTHING METAL SURFACE BY LOWTEMPERATURE FIELD EVAPORATION
UHV conditions, T=21 K
Surface of tungsten nanotip before
treatment
Atomic smoothing during field
evaporation
Destruction at mechanical stress due to high electric field
F = 60V/nm, σ = 20 GPa (Theoretical Strength)
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SURFACE FORMING BY FIELD
DESORPTION (Computer modeling)
Nanotip [100] orientation
Pulse field desorption
Evaporation rate 0.01 nm/s
Alternative field evaporation of nanotips
KIPT Kharkov, together with Oxford University,
UK (Prof. G.Smith) and Hahn-Meitner-Institute,Berlin
(Dr.N.Wanderka)
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PHENOMENON OF LOW-TEMPERATURE
FIELD EVAPORATION IN DIELECTRIC
LIQUIDS
High-field forming without mechanical destruction
Electron microscopic image
of W microtip after high-field
treatment in liquid nitrogen
a
b
FIM images W nanotips formed by evaporation
in liquid nitrogen at 0.4 kV (a) and 1.2 kV (b).
Joint patents with Dr. R. Forbes, University of Surrey School of Electronic,6 UK
Dr. N. Wanderka, Hahn-Meitner-Institute, Berlin, Germany
RATES OF FIELD EVAPORATION IN
DIELECTRIC LIQUIDS AND ACTIVE
GASES
5
500
4
1
1
3
-10
2
300
Ke, 10 m/s
Ke, nm/s
400
200
2
100
1
0
0
10
20
30
40
50
F, V/nm
Evaporation in UHV (1) and
liquid nitrogen (2) of W
Blunting of nanotips
60
2
0,4 0,5 0,6 0,7 0,8 0,9 1,0
F/F0
Gases hydrogen stimulated
evaporation. Nb-Ti at 0.82 (1) and
0.25 (2) Pa
Sharpening of nanotips
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Joint patent with Dr. R. Forbes, University of Surrey School of Electronic, UK
FIELD EVAPORATION IN ACTIVE GASES
Sharpening of nanotips
10 s
15 s
5s
0s
R=2 nm
W – N2
Nanotip [100] orientation
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HIGH-FIELD FORMING OF STM
MICROPROBES AND MICROSURGICAL
INSTRUMENTS
STM probe before (a) and after (b) high-field sharpening
a
Graphite surface
image obtained in the
STM with
an atomically smooth
microprobe
b
a
b
Microknife (a) and Satoknife (b)
Segment of market related to
medical instrumentation9is
about 100000 per year
PROBLEM OF FIELD-EMISSION NONUNIFORMITY
CNT-film (random)
CNT bundles (aligned)
CNT (regular array)
SEM image of cross-section
of film
Large-scale field emission
J.Chen et al,Ultramicroscopy
95 (2003) 153
Top-down view
Collapsed CNTs
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W.Yu et al, Nanotechnology
16 (2005) S291
Next step proposed
- HIGH-FIELD FORMING OF CARBON,
SILICON, AND OXIDE NANO-SIZED OBJECTS
- SELF-CONSISTENT HIGH-FIELD
FORMING OF NANORELIEF
Field-ion emission of nanofibre carbon emitter
a
b
c
Nanorelief before (a), during (b) and after (c) stimulated field evaporation11
OUR TEAM
Mikhailovskij Igor, Dr. Sci., Prof., Leading researcher
Mazilova Tatjana, Dr Sci, Senior researcher
Ksenofontov Vjacheslav, PhD, Senior researcher
Velikodnaya Olga, PhD, Researcher
Sadanov Evgenij, PhD, Researcher
Thank you for your attention!
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