A 10-a editie a Seminarului National de nanostiinta si nanotehnologie

18 mai 2011 Biblioteca Academiei Romane

The versatility of catalytic LCVD technique to grow carbon nanotubes

1st Step:the preparation of the substrate

2nd Step:synthesis of nanotubes by LCVD

Sample Ar window

sccm

C2H2

sccm

SF6

sccm

Ar (in mixture)

sccm

Pressure

mbarr

PL

W

Time

min

CNT lenght

1D 1000 30 5 - 80 80 3 3-4 µm 1F 1000 30 10 - 80 80 3 300-400 nm 1E 1000 30 10 5 80 80 3 200 nm 10A 1000 30 15 5 80 80 3 > 500 µm

There is a compromises between SF6 and Ar mixture

SF6/Ar MIXTURE INFLUENCES

LASER POWER AND PRESSURE INFLUENCES

By increasing PL increase the length of CNT and sometime increase also the thickness By increasing pressure increase the length of CNT

Sample Ar window

sccm

C2H2

sccm

SF6

sccm

Ar (in mixture)

sccm

Pressure

mbarr

PL

W

Time

min

CNT lenght

10A 1000 30 15 5 80 80 3 > 500 µm 1-7 1000 30 15 5 80 60 3 110 µm 1-9 400 30 15 5 40 40 3 80 µm

1-18 400 30 15 5 40 30 3 30 µm 1-11 400 15 5 - 40 40 3 40 µm 1-19 400 15 5 - 40 30 3 40 µm 1-12 400 10 5 - 40 40 3 60 µm 1-14 400 10 5 - 40 30 3 2-3 µm

Laser beam 12 mm

Sample Ar windowsccm

C2H2sccm

NH3sccm

Pressurembarr

TemperatureoC

PLW

Timemin

10-7 1000 30 90 100 900 27 210-6 1000 30 90 100 430 13 210-1 1000 30 90 450 430 28 210-2 1000 30 180 100 430 15 210-3 1000 30 180 450 430 20 210-4 1000 30 270 100 430 25 210-8 1000 30 270 450 430 28 2

Laser beam 1 mm

The catalytic LCVD offers the advantage of high versatility and control since it separates the catalyst preparation from the catalytic growth of nanotubes.

The possibility of controlling the size of the laser spot on the substrate allows to heat the substrate very locally and to produce CNTs for various applications.

The high versatility as concerning the catalyst nature and preparation.

A cold wall reactor in which the CO2-laser radiation is heating both the silicon substrate and the gas phase.

High deposition rates, that are favorable for scale-up production of CNTs

LCVD was recently used to fabricate lines of CNTs and to control the orientation of the tubes by use of an electric field

Laser polarization could significantly influence the selective growth of CNTs.

Compared with the post-growth manipulation, the in situ growth is more suitable for large-scale device fabrication.

In order to avoid CNT damage, the temperature was adjusted from 900 oC to about 430 oC (by acting on the laser power)

At lower pressure CNT are oriented in the direction of gas flowOn the catalytic growth of CNT by LCVD technique:On the catalytic growth of CNT by LCVD technique:

1.1.NH3 additive gas is more efficient than SF6: NH3 additive gas is more efficient than SF6:

unwanted carbon deposits are not formed unwanted carbon deposits are not formed the mean diameters are much thinnerthe mean diameters are much thinner

2.2. The formation temperature is relatively low.The formation temperature is relatively low.

Perspective

Iuliana Morjan1,2, Ion Morjan2, Rodica Alexandrescu2, Catalin Luculescu2, Eugeniu Vasile3, Monica Scarisoreanu2, Anca Barbut2

1 IMT-Bucharest, 126A, Erou Iancu Nicolae street, 077190, PO-BOX 38-160, 023573, Bucharest, ROMANIA2 National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor St, P.O. Box MG-36, 077125, Bucharest, Romania

3 METAV-R&D, 31 C.A. Rosetti St., 020011 Bucharest, Romania

Acknowledgement: some of the results were obtained in the frame of the Project POSDRU/89/1.5/S/6370