more energy to cause ionization collisions, reducing the need for secondary electrons to sustain the discharge, (c) The electron movement delivers a short current pulse when the cathode is positive and smaller current when the cathode is negative, resulting zero average current. RF voltage can be coupled through any impendence, so that the electrodes need not be a conductor. The typical RF frequency used is 13.56 MHz.

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Figure 39.5: Motion of the electon under the magnetic field with (a) electron velocity and magnetic field directions are parallel, (b) electron velocity and magnetic field directions are angled at θ.

(3) Magnetron sputtering technique:

Electron motion in parallel electric and magnetic fields:
What happens when the magnetic field of strength B is superimposed on the electric field E between the target and substrate? Electrons within the dual field environment experiences the well-known Lorenz force in addition to the electric force, i.e.,

(1)

where, q is charge, m – mass, and v – velocity of electron.

Case I : E and B is parallel. When electrons are emitted exactly normal to the target surface and parallel to both fields, then it results v×B→0 (see Figure 39.5a). Electrons are only influenced by the electric field, which accelerates them towards anode.

Case II : E=0 and only B field. If an electron is launched from the cathode with velocity v at an angle θ with respect to B, then the electron experiences a force qvBsinθ in direction perpendicular to B. The electron orbit in a circular motion with a radius r is determined by a balance of the centrifugal force and Lorentz force involved (see Figure 39.5b).

........................ (2)