Time-resolved electric probe techniques in radio frequency plasmas

Time-resolved cross-sectional variation of plasma potential and electron energies were measured in a parallel-plate capacitively coupled argon discharge at 400 mTorr. Movable capacitive and shielded Langmuir probes were scanned between the plates and used to obtain I-Vcharacteristics at the plasma potential minima and maxima. The variation of plasma potential was sinusoidal at the center of the discharge producing a sheath at both electrodes. During the plasma potential minima and maxima an electron beam component of the electron energy distribution at 5–26 eV was seen. The energy of the beam increased, and its magnitude decreased, traversing through the sheath region. Electron beam energy variations with pressure (200 mTorr-1 Torr) are also discussed.