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Vjachslav Ksenofontov

PhDsenior researcher

mikhailovskij@kipt.kharkov.ua

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 desorptionNanotip [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,

10-1

0m

/sF/F0

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 s5 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 CNTsW.Yu et al, Nanotechnology

16 (2005) S291

Large-scale field emissionJ.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!