الفهرس 
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Abstract
A DC- Magnetron Sputtering unit was designed and successfully operated with a low DC-current (cold cathode ) glow discharge using Ar and He gases .
The electrical characteristics of the DC- glow discharge were
studied e.g. :- the I-V characteristic curves , the V-P curves , the potential distribution and the electric field distribution along the discharge . The I-V characteristic curves confirmed that the electric discharge was mainly in the normal glow discharge region ( la 10 mA ) in the pressure range of ( 2-4 mbar ) , while at lower pressure the discharge can be described to be subnormal glow discharge (la 2 mA). It is concluded that , the breakdown voltage was found to be decreased by increasing the gas pressure at constant discharge current .
The potential distribution defined accurately the thickness of the cathode fall region (de) . ”de” was about 1-3 mm. depends.upon the gas pressure (P) . The data agree fairly with the theoretical reiiit.Sn bZiween de and P . The axial electric field distribution confirmed the presence of higher field at the cathode fall region , which decreases sharply towards the negative glow and the positive column regions . In the positive column region , the electric field was weak and nearly constant . The strong electric field in the cathode fall region accelerates the electrons inward the glow discharge .
In order to define the optimum conditions of DC- glow discharge , the parameters of the formed discharge.were measured accurately . The electron temperature Te , the plasma density Ne , the electron energy istribution function F(E) , the degree of ionization and the plasma models were determined in the different three regions of the glow discharge (i.e. the cathode fall , the negative glow and the positive column regions ) , using electric probes and spectroscopic techniques .
It is concluded that , at the edge of the cathode fall region two groups of electrons having temperature in the range of 5-12 eV , and density of 4x108 - 1.4x108 cm-3 were found . In the negative glow region , two groups of electrons having a temperature range of 5-8 eV and density of 6.6x108 - 2.2x108 cm-3 , were detected . The presence of these two groups were attributed to ”runaway” process in the weakly ionized gases , whereas , the criteria for electron acceleration without doing any collisions were quite satisfied in this region . Meanwhile , these electrons collide with neutral atoms in the negative glow region and produced secondary electrons with different temperatures .
It is concluded that the thermalization time between the two groups of electrons was longer than the required time for electrons to leave the cathode fall region . Therefor , electrons have no chance to redistribute themselves in one Maxwellian distribution group . In the positive column region , only one group of electrons was detected , which has a temperature in the range of 4-7 eV and density in the range of 3x108 - 1 .2x108 cm-3 . Unlike the cathode fall and negative glow regions , the thermalization time was short enough for electrons to redistribute themselves in one Maxwellian distribution group .
To overcome the shortcomings in the density measurements by probes , four different methods were used including the classical method ( Kagan and Perel method ) , log-log , integration of the electron energy distribution function (EEDF) and the double probe methods . It is concluded that , the integration of the EEDF method produced the most reliable values of Ne since it considered the real distribution function . Values obtained by the log-log method agree fairly with the integration of the EEDF method . The classical method produces higher values of Ne , by a factor of 2-3 than those of the a fore mentioned methods. This may be attributed to :-
I- Ions were assumed to inter the sheath with a velocity of ( kTe / mnial/2
2-Sheath area As must be used instead of the geometrical area of the probe (Ap) , and
3-The effect of the secondary processes ( e.g. emission of secondary electrons from the probe surface ) .
It is concluded that , values of Te decreased by increasing the gas pressure , while Ne increased by increasing the gas pressure . This may be attributed to the increase in the number of electron - atom collisions and consequently , increasing the rate of ionization at higher pressure .
The spectroscopic technique depends upon the ratio of He singlet to triplet lines intensity was used to measure Te . It is concluded that , secondary processes effect the intensity of the lines 5048 , 4713 , 4437 and 4121 A° and consequently the estimated values of Te . An improvement in the method was carried out by using lines 5016 and 3889 A°. Effects of secondary processes on the intensity of these lines were estimated and taken into consideration . Moreover , a relation between Te and the ratio of the intensity of these two lines is computed . Reliable data of Te are thus obtained which agree fairly with the probe measurements .
The spectroscop The spectroscopic measurements indicated that the degree of ionization was less than 6x10-4 . This was confinned by the probe measurements , therefore , the DC- glow discharge was considered to be a partially ionized gas .
The plasma models in the three different regions of the glow discharge were discussed . It is found that , the plasma formed in the
positive column region for Ar and He gases is in Steady State Corona model.