Presentation on theme: "1 Vjachslav Ksenofontov PhD senior researcher National Scientific Centre Kharkov Institute of Physics and Technology, Kharkov,"— Presentation transcript:
1 Vjachslav Ksenofontov PhD senior researcher National Scientific Centre Kharkov Institute of Physics and Technology, Kharkov, Ukraine High-field technology for processing of nano-sized objects
2 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.
3 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.
4 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)
5 SURFACE FORMING BY FIELD DESORPTION (Computer modeling) Pulse field desorption Nanotip  orientation 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)
6 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
7 RATES OF FIELD EVAPORATION IN DIELECTRIC LIQUIDS AND ACTIVE GASES 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 nanotips Sharpening of nanotips Joint patent with Dr. R. Forbes, University of Surrey School of Electronic, UK
8 FIELD EVAPORATION IN ACTIVE GASES Sharpening of nanotips 0 s 5 s 10 s 15 s Nanotip  orientation R=2 nm W – N 2
9 HIGH-FIELD FORMING OF STM MICROPROBES AND MICROSURGICAL INSTRUMENTS STM probe before (a) and after (b) high-field sharpening a b Graphite surface image obtained in the STM with an atomically smooth microprobe a b Microknife (a) and Satoknife (b) Segment of market related to medical instrumentation is about per year
10 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
11 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 bc Nanorelief before (a), during (b) and after (c) stimulated field evaporation
12 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!