24 icnts conference-bologna, italy, 2008 structure and properties of metallic wires obtained as...

24 ICNTS Conference-Bologna, Italy, 2008

Structure and properties of metallic wires obtained as replicas of etched ion

tracks in polymer matrixesZagorski D.L., Oleinikov V.A.,Bedin S.A., Rybalko O.G.,Mchedlishvili

B.V.

Institute of Crystallography, Moscow, Russia

Our experiments and this presentation consists of 4 main parts

1. Preparation of polymer matrixes 2. Electrodeposition of metals into the pores 3. Microscopy investigation 4. Emission properties.

24 ICNTS Conference - Bologna, Italy, 2008• TEMPLATE MATRIXES

One of the applications of ion track technologies is obtaining of track membranes (or nuclear filters)-• Could be used as - filters with unique properties. • - another application- as the matrixes for template synthesis of nanomaterials.• This work is devoted to some new aspects of this idea . • We started with commercially available TM-

• 3

Commercial TM which are developed for filtration are not the best material for template synthesis- So, specially prepared matrixes are needed for replication.• Lower density and parallel arrangement of the pores- could be easily obtained during irradiation (orientation and fluence): • We also could vary the shape of the pores – the most interesting is conical shape.

Paper Oleinikov V., Tolmachyova Yu., Berezkin V., Vilensky A., Mchedlishvili B.,. PET track membranes with conical pores: etching by water-alcohol alkali solutions.

Rad. Meas.; 1995 25, N1-4, 713-714.

The ways of obtaining of conical pores-: - irradiation by “light” ions (Ar)

- etching in water-alcohol alkali solution

How to make conical pores?

cross-section of track membrane

High density, different (random)inclination)cross-section of template matrix

Low pore density, parallel orientation

Dependence of cone half-angle on temperature for different concentration of ethanol in etching solution

1-without ethanol, 2-30% of ethanol,3- 50% of ethanole, 4- 80% of ethanole, 5- 96% of eth.

24 ICNTS Conference - Bologna, Italy, 2008

Two effects 1.The acceleration of bulk etching of polymer – due to increasing of ionic force of solution and reducing of electrostatic potential at the surface.2. The reducing of etching speed along the track – Ba-ions have higher adsorption to the track areas and reduce the etching of the tracksIn the case of etching of latent tracks it leads to increase of cone angle.This is the way of making conical pores and varying of their shape.---

CONICAL PORESHow to make conical pores?? New method - addition of salts ion into the etching solution. Addition of Ba 2+ ions to etching solution (0,25mol/l KOH + 0,1 mol/l BaCl BaCl 2)

Etching of latent trackPolymer (PET) in etching solution

PAPER Electrolytes for etching of heavy ions latent tracks in polyethyleneterephtalate. Vilenski F., Kochnev Yu., Vlasov S., Mchedlishvili B. // Surface, 2008, N10 (Translated from Russian “Poverchnost”)

time, s


• Second Step - Galvanic Process• Electrodeposition of metals- Cu, Ni and Co- into the pores • Standard galvanic Cell and standard sulfuric electrolytes were used CuSO4 -135 g/l and H2SO4 – 15 g/l,

NiSo4 7H2O-180 g/l, NH4Cl-25g/l, H3BO3 -30g/l,CoSO4 – 300 g/l, H3BO3 – 40 g/l NaCl – 6 g/l

• Most of the results presented here are for copper microwires

Main problems Ni –formation of hydrogen, we used the horizontal orientation and ultrasound treatment for removing of hydrogen bulbs.

Co –low conductivity of electrolyte,we used special additions to electrolyte and/or change potentiostatic regime to galvanostatic.

Typical curve for filling of through-pores – obtaining of cylindrical wires (for Cu,Ni,Co)

The last picture is for the case of overgrowth-the caps are formed at the end of wires

Typical curve for filling of conical dead-end-pores – obtaining of conical wires

In this case we have to use all the processes (deposition of conductive layer and electrodeposition itself) at one side.

first seconds corresponds to stabilization of galvanic process then-Two parts-first-increasing of the current-filling of dead-end pores,

second-growing of metal at the flat surface//

I, m

A

I, m

A

time, s


Third Step-Microscopic Investigation.Atomic-Force Microscopy

Just after deposition we obtained metal wires embedded in polymer matrix. In our mind this “composit material” is interesting for practical application –so it was tested by AFM

• Results for cylindrical wires pass through all the polymer film• The main problem was to find metal, to distinguish metal from polymer.• WHEN WE SEE hillock at the topographic image of surface- is it metal or polymer globula???• we have to use additional modes• AFM - Tapping mode. The additional mode of phase-contrast indicates the shift of the phase of vibration of cantilever due to

contact with the surface. This shift is determined by interaction with the surface and it is different for polymer and metal. • AFM- Contact mode. When using contact regime we could got additional information by measuring lateral force – this force

determined by friction between cantilever tip and surface and depends on surface properties. Lateral force • determine bending of cantilever


Atomic-Force Microscopy- Tapping

Tapping-topography Phase-contrast


• Atomic-Force Microscopy -Contact

Contact mode Lateral force mode

Red circles – metallic wires, green circle – polymer relief

24 ICNTS Conference - Bologna, Italy, 2008• Atomic-Force Microscopy –spreading resistance

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Topography Spreading resistance mode

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AmVMax

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40030:

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nAmVMax

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5.110:

• Conductivity, I-V curves

Individual wire Bulk

The great difference between individual and bulk conductivity is found ???


Microscopic Investigation. SEM images of free-standing metallic microwires

There were microwires embedded into polymer matrix. Now about free-standing metallic wires - that is after removing of the polymer matrix.

Cylindrical microwires

Conical microwires


Microscopic Investigation.

SEM images of free-standing metallic microwires

Conical microwires

SEM- TESLA BS-340 (Czechoslovakia)

We obtained the cylindrical wires with diameter 0.1-2.0 mcm, high up to 10 mcm, and conical wires with the lower base 0.1-1.5 mcm,high up to 5-10 mcm. The cone angle-5 -25 degr.Surface densities were 10**6 – 10**9 /cm2


• Forth Step- Emission properties• It is known that obtained ensembles of microwires could be used

for emission of electrons (“cold cathodes”) - Due to increasing of electrical field near the end of the wires

• In our work we demonstrated the possibility of ion emission from this wires and that this effect could be used in mass-spectroscopy–these results were presented at the previous ICNTS 2 years ago

• The idea of method-

Molecules could be separated from each other, ionized and desorbed from the structured surface. After that - they could be accelerated by electrical field and

analyzed in mass-spectrometer.


Paper: The study of the desorption/ionization from the replicas of etched ion tracks. Oleinikov V., Zagorski D., Bedin S., Volosnikov A., Emelyanov P., Kozmin Y., Mchedlishvili B. //

Radiation Measurements, 2008,V.43, p.S635-638.

Time - of - flight Mass-spectrometerTime - of - flight Mass-spectrometer

Mass-spectrometers VISION-2000 (UK) and BRUKER TOF/TOF (Germany) were used in our work


Emission properties

Laser Pulse~ 5 ns)

Desorbtion/Ionisation from surface

Elec

tric

al F

ield

Surface Probe (Analyte- biological molecules)



Now we investigatedNow we investigated the intensity of ion emission. Substrate with gramicidin (probe -1 pl) was put into the mass-spectrometer (Vision-2000, the intensity of ion emission. Substrate with gramicidin (probe -1 pl) was put into the mass-spectrometer (Vision-2000,

ThermoBioanalysis, UK) and irradiated by pulses of nitrogen laser (337 nm),ions were analyzed by time-of -flight mass analyzer ThermoBioanalysis, UK) and irradiated by pulses of nitrogen laser (337 nm),ions were analyzed by time-of -flight mass analyzer The 0.25 The 0.25 μμl drop of water-methanol solution of gramicidin (concentration – 0.01 - mg/ml) was deposited on copper substrate (thickness of l drop of water-methanol solution of gramicidin (concentration – 0.01 - mg/ml) was deposited on copper substrate (thickness of gramicidin layer was approximately 20-30 nm).gramicidin layer was approximately 20-30 nm).

The dependence of mass-spectra intensity on the probe concentration

1163.307

25_03_08\gramicidine 0_01 mg_ml CuM12-1 40\1SRef

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.u.]

1203.623

1265.634


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1163.191

1225.257

2253.626

25_03_08\gramicidine 5 mg_ml CuM12-1 40\1SRef

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5 mg/ml

Emission properties

1163.307


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1203.623

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2253.626


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5 mg/ml


The dependence of mass-spectra intensity on power of laser pulse

1162.873


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Emission properties

24 ICNTS Conference Bologna, Italy, 2008

The dependence of mass-spectra intensity on the surface density of wires

1163.157

1203.121

10_09_07_new laser power(30%)\gramicidine2 5 mg_ml Cu 76\1SRef

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1162.873

1202.866


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2,3·10 8 cm-2

4· 106 cm-2

For higher surface density of wires we obtain lower signalIt could be explained by superposition, overlapping of the fields of neighboring wires and damping, suppression of the field tension of neighboring wires

Emission properties


• Dependence of emission signal on the shape of wires and metal

• It must be mentioned that all these results were obtained for the substrates with ensembles of wires of cylindrical shape. For conical wires we obtained more intensive emission the better results --3 -5 times more -were for cones with aspect ratio it can be explained by increasement of electrical field at the ends of the wires with small radius of curvature (so-called lighting-rod effect) BUT – for conical- we have bad reproducibility.

• For wires cowered by silverwires cowered by silver the signal intensity increase – average 2 times.

• Dimer and trimer formation was detected

• Degradation• Now about stability-Are our structures stable enough?• Fig demonstrates structures before laser irradiation (A) and after laser irradiation (B) (Laser power 1mW)

Emission properties

•Degradation of microwires during emission –we could see melting and bending of the wires. Moreover this process is step-by-step (not simultaneously, but one after another, gradual). This degradation, destruction process could be the reason of rather low efficiency and instability of emission.


• Conclusions- • - Conical pores and their metal replicas were obtained. Their

geometrical, and emission features were investigated - The possibility to detect metal imbedded into the polymer and to measure I-V dependences for individual microwire were demonstrated.

• - The process of ionized molecules emission from free-standing microwires was investigated. It was shown that intensity of formed ion beam increases with increasing of power of laser pulse and with increasing of the mass of probe.

At the same time this intensity decreases with the increasing of surface density of wires. The last could be caused by superposition of the fields of neighboring wires in the case of their high density.- Dimer and thrimers formation was detected. This result demonstrates the high sensitivity of method. - Process of destruction of wires during the emission could be the reason of instability of ion emission.

Formation of Ensembles of Cylindrical Microwires

a) Sputtering of thin copper layer (2) at the surface of TM (1) – conducting layer is formed.

b). Galvanic deposition of copper into pores.

c). Deposition of copper from the opposite side – reinforcement of the obtained structure.

d). Removing of polymer matrix – by etching in strong alkali solution

Sulphate electrolyte CuSO4 -135 g/l and H2SO4 – 15 g/l

Etching solution 240 g/l

Formation of Ensembles of Conical Microwires

a). Sputtering of thin copper layer (2) at the surface of TM (1) – conducting layer is

formed.

b). Galvanic deposition of copper into pores.

c). Further deposition for reinforcement of the obtained structure.

d). Removing of polymer matrix – by etching in strong alkali solution

.

Enhancement of electric field near the end of microwires. Left- low surface density of microwires. Right- high surface density of

microwires

24 icnts conference-bologna, italy, 2008 structure and properties of metallic wires obtained as...

Documents

conical pores

case of etching

reducing of etching

conical shape

gl nacl

template matrixes

track baions

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