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Vjachslav Ksenofontov
PhDsenior researcher
National Scientific Centre “Kharkov Institute of
Physics and Technology”, Kharkov, Ukraine
High-field technology for processing of nano-sized objects
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Developed technology for nano-scaled 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 super-high electric field.
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SMOOTHING METAL SURFACE BY LOW-TEMPERATURE 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)
Pulse field desorption
Nanotip [100] orientation
Evaporation rate 0.01 nm/s
Alternative field evaporation of nanotipsKIPT 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
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, UK Dr. N. Wanderka, Hahn-Meitner-Institute, Berlin, Germany
High-field forming without mechanical destruction
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RATES OF FIELD EVAPORATION IN DIELECTRIC LIQUIDS AND ACTIVE
GASES
0,4 0,5 0,6 0,7 0,8 0,9 1,00
1
2
3
4
5
2
1
Ke, 1
0-1
0m
/sF/F
0
10 20 30 40 50 600
100
200
300
400
500
Ke,
nm
/s
F, V/nm
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Gases hydrogen stimulated evaporation. Nb-Ti at 0.82 (1) and
0.25 (2) Pa
Evaporation in UHV (1) and liquid nitrogen (2) of W
Blunting of nanotipsSharpening of nanotips
Joint patent with Dr. R. Forbes, University of Surrey School of Electronic, UK
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FIELD EVAPORATION IN ACTIVE GASES Sharpening of nanotips
0 s
5 s
10 s 15 s
Nanotip [100] orientation
R=2 nm
W – N2
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HIGH-FIELD FORMING OF STM MICROPROBES AND MICROSURGICAL
INSTRUMENTSSTM probe before (a) and after (b) high-field sharpening
a b
Graphite surface image obtained in the STM with an atomically smooth microprobe
a bMicroknife (a) and Satoknife (b)
Segment of market related to medical instrumentation is
about 100000 per year
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PROBLEM OF FIELD-EMISSION NON-UNIFORMITY
CNT-film (random) CNT (regular array)
Collapsed CNTs
W.Yu et al, Nanotechnology 16 (2005) S291
Large-scale field emission
J.Chen et al,Ultramicroscopy
95 (2003) 153
CNT bundles (aligned)
SEM image of cross-section of film
Top-down view
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Next step proposed - HIGH-FIELD FORMING OF CARBON,
SILICON, AND OXIDE NANO-SIZED OBJECTS - SELF-CONSISTENT HIGH-FIELD
FORMING OF NANORELIEFField-ion emission of nanofibre carbon emitter
a b c
Nanorelief before (a), during (b) and after (c) stimulated field evaporation
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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!
