Striations in a radio frequency planar inductively coupled plasma

Photographic evidence is presented for azimuthal structure in cylindrical radio frequency (RF) planar inductively coupled plasmas. Observations made in a high aspect ratio chamber (antenna radius large compared to height of plasma volume) show azimuthal striations (periodic modulations in emitted light intensity) in an argon discharge. These striations, reported here for the first time, have serious implications for discharge uniformity under some conditions (discharge shown at 300 W RF power, 85 mtorr). A comparison to positive column striations in dc glow discharges shows some similarities, although a complete explanation will require consideration of RF effects.