Preparing of Diamond in the presence of CH4-H2 in a cold plasma produced by a magnetron.
Habibi,Maryam 1 ;Ghoranneviss,Mahmood 1 ;Naranji,Reza
2
1.Plasma Physics Research Center, Science & Research Branch, I.A.University, P.O.Box 14665-678, Tehran, Iran.
2.I.A.University, Ardabil Branch, Ardabil, Iran.
Abstract
In this paper we have prepared diamond by
depositing the mixture of CH4 and H2 (%98 H2 and
%2 CH4) on silicon substrate in a cold plasma
produced by a DC magnetron.
The percentage of the mixture is %98 H2 and %2
CH4 at the pressure of 5*10^-3 Torr. Different
pressures and different exposure times have been
examined and different analyser such as
SEM,Raman Spectrum and XRD have been used to
investigate the results.
1.Introduction
Diamond thin films have been formed by DC plasma
chemical vapor deposition from a gaseous mixture of
methan 2% and Hydrogen 98% .
It has been confirmed that diamond can be grow from
the vapor phase at low pressure where graphite in the
stable modification of carbon.The main growth
methods used are hot filament chemical vapor
deposition and plasma with the deposition of above gas
mixture.
It is said that the active species for diamond synthesis at
low pressure are methyl radicals and hydrogen atom in
the gas temperature region(<2500 K).
In this paper , the growth of diamond thin films by the
DC plasma CVD method will be described. The
characteristics of DC plasma measured by the
Langmuir double probe method and were characterized
using X-ray diffraction, scanning electron microscopy.
The plasma plays an important role during deposition of
diamond films by electron assisted chemical vapor
deposition.
2.Experimental
The fig.1 shows the schematic diagram of electron
assisted CVD apparatus. In this apparatus,the voltage
applied on negative and positive plates of cathode and
anode , emits the electrons from cathode to anode , that
anode and cathode used are made of AL.
The reaction gases which are CH4 and H2 are fed to the
vacuum chamber through the thermal mass flow
controller. The pressure of the reaction gas in measured
using a diaphragm gauge. A substrate is silicon is set on
the anode.
The vacuum chamber is evacuated to 10^-4 Torr and
H2, CH4 introduced in to the chamber , In this case we
adjust pressure to 10^-2 Torr then DC voltage is applied
to start discharge. Then the gas mixture of 2% CH4 in
H2 is applied continuously at the gas flow.
3.Results
The diamond films have been prepared an silicon with
discharge voltage 2 kv , discharge current 50-200(mA),
temperature of filament 2000 0 C.The structure of
prepared films is analyzed by means of X-ray
diffraction scanning electron microscopy. The X-ray
diffraction,SEM and Raman Spectrum are shown in
fig.2-4.
Fig.5 shows that continuous polycrystalline diamond
film is formed and has good crystal habit..
4.Conclusion
Diamond films can be formed by the DC plasma CVD
method. The polycrystalline diamond films can be
prepared in the wide range of technology parameters.
By knowing diagnostics of the plasma parameters is
useful for providing essential information of PCVD
and controlling preparation of high quality diamond.
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Fig.1 – Schematic diagram of electron assisted CVD apparatus.
Fig.2.2 – Shows the X-ray diffraction pattern of prepared film.
Fig.3 – SEM picture of Diamond film
Fig.4 – Raman Spectrum obtion from coating DLC on silicon substrate.