The basic operational factors of magnetron atomizing systems - the voltage on electrodes, discharge current, current density on a target and specific power, value of magnetic field induction and working pressure. From value and stability of the listed parameters which are mutually connected among themselves, depend stability of the discharge and reproducibility of covering deposition process. MAS belong to low-voltage systems of dispersion. The supply voltage does not exceed 1000 V. The working voltage makes 300 … 700 V, on a target the negative potential applies, and on the anode submit small positive displacement (40 … 50). In some systems submission of a negative voltage on the substrate (up to 100) for dispersion with displacement realization [14] is provided.
The discharge current depends on many factors: a working voltage, pressure of working gas, induction of magnetic field, configuration magnetron system, sprayed material. The current density on a target is very great: 80 … 200 мА/sm2 [15]
MAS can work in a range of pressure from 10-2 up to 1 P and above. The major parameters, in many respects defining character of the discharge in it, the geometry and value of magnetic field, which induction at a target surface is 0.03 … 0.1 tesla.
The operation effectiveness of magnetron atomizing system depends on a correct choice of working parameters, and stability of these parameters defines constancy of film deposition rate and reproducibility of received films properties. Necessary film deposition rate in magnetron system with sufficient accuracy can be kept up due to constancy of such parameters of process, as discharge current or power input. The power supply can carry out these functions owing to what management of final film thickness is achieved if deposition time [14] is preset.
In designed installation magnetron atomizing system provides deposition of functional (corrosion-proof and decorative) coatings with thickness up to 0,5 microns on oil filters covers. As such covering titanium nitride has been chosen. Thus, a material of the cathode-target is the titan, working gas - nitrogen.
Questions of the discharge theory in magnetron atomizing system and methods of their technological and design parameters calculation are worked poorly. Complexity consists in that these systems use non-uniform crossed electric and magnetic fields. It makes practically impossible the exact analytical description of the phenomena occurring in the magnetron atomizing system discharge.
The Important parameter of deposition process is speed of product processing for reception of demanded covering thickness on it that is speed or factor of target dispersion which depends on bombarding ions energy. Energy of ions, in turn, depends on the accelerating potential. As the electric field is non-uniform, the accelerating potential is not equal to voltage on electrodes. In figure 3.2 distribution of potential in discharge gap is shown.
Figure 3.2 Potential distribution in discharge gap of magnetron atomizing system with cylindrical electrodes: 1 - area with positive spatial charge at the cathode, 4 - area with a negative spatial charge at the anode, 2 and 3 - simultaneous existence of both areas.
At an induction of magnetic field about 0.1 tesla in the discharge there are obviously expressed areas both cathodic, and anode falling of potential. Researches have shown that such discharge is rather effective for materials dispersion. The accelerating potential makes 0.6 … 0.8 from voltage on electrodes [14].
Thus, having accepted voltage on electrodes U=750 V, we shall receive accelerating voltage 600 V.
Influence of the magnetic field induction and working pressure upon the discharge was above noted. On the basis of the analysis of MAS parameters dependences where accepted following values:
В=0.1 tesla, р=0.133 P,
Uр=600 V.
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