Nonmonotonic dependence of plasma density on gas pressure in magnetron discharge with a boron target

The paper presents the results of studying a magnetron discharge with a boron target at a constant current of 50 mA and a working gas pressure in the range of 0.1-2 mTorr. It is experimentally shown that both in the case of a boron target and in control experiments with a copper target, a nonmonotonic dependence of the discharge plasma density on pressure is observed with a minimum of density in the pressure region of about 0.3 mTorr. It is concluded that such a nonmonotonic dependence is due to the influence of two opposite trends: a decrease in gas ionization with a decrease in pressure from 1.2 to 0.3 mTorr, at which significant changes in the discharge parameters do not yet occur, and an increase in ionization due to an increase in the energy and number of γ-electrons from the cathode (target), as well as the plasma electron temperature at a sharp increase in the discharge burning voltage with a further decrease in pressure from 0.3 to 0.1 mTorr.

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