CHARGED-PARTICLE TRANSPORT IN HARMONICALLY VARYING ELECTRIC-FIELDS - FOUNDATIONS AND PHENOMENOLOGY

The transport theory of ions and electrons in an oscillating electric field, typically at radio frequencies, is of interest both as a proble m in basic physics and for its potential for application to modern tec hnology, e.g., plasma processing. Our research has been motivated by b oth these considerations, but the present paper concerns theory and fo cuses on Boltzmann's kinetic equation in particular. We note that as f ar as kinetic theory is concerned, any substantial advances on the pio neering work of Margenau and Hartmann nearly fifty years ago have been remarkably limited in comparison with the extensive, systematic devel opment of d.c. transport theory over the past two decades. Our goal ha s been to develop a comprehensive theory of a.c. charged particle tran sport, at a level of sophistication comparable with the d.c. theory, a nd the first steps are reported in the present paper, which deals with theoretical foundations and phenomenology. After examining the broade r implications of space-time symmetries, namely, parity and phase-reve rsal invariance, we proceed through low-order moments of Boltzmann's e quation, with collision terms approximated in the same way as for d.c. momentum-transfer theory, and look for relationships, however approxi mate, connecting experimentally measurable quantities, and otherwise a ttempt to shed light on transport phenomena peculiar to harmonically v arying electric fields. In this way we obtain: (a) A full set of momen tum-energy balance equations for both ions and electrons, to be solved simultaneously with Poisson's equation where appropriate; (b) A gener alisation of Wannier's energy relation for ion swarms in an a.c. field ; (c) Generalised Einstein relations for cycle-averaged electron swarm diffusion coefficients; (d) information about a.c. negative different ial conductivity and the anomalous character of anisotropic diffusion in a.c. fields; (e) A procedure for adaptation of d.c. experimental sw arm data to a.c. swarms and r.f discharges. The discussion is at the s emiquantitative level, with emphasis on physical understanding. (C) 19 97 Academic Press.