The momentum transfer cross section for electron-argon collisions in the range 0-4 eV has bel(n derived from an analysis of recent measurements of DTIIl as a function of EIN at 294 K (Milloy and Crompton 1977a) and Was a function of EIN at 90 and 293 K (Robertson 1977). Modified effective range theory was used in the fitting procedure at low energies. An investigation of the range of validity of this theory indicated that the scattering length and effective range were uniquely determined ,and hence the cross section could be accurately extrapolated to zero energy.It is concluded that for 8 ,;;; O· 1 e V the error in !he cross section is less than ± 6 % and in the range 0·4 ';;;8 (eV) ,;;; 4-0 the error is less than ± 8 %. In the range 0·1 < 8 (eV) < 0·4 the presence of the minimum makes it difficult to determine the errors in the cross section but it is estimated that they are less than -20 %, + 12 %. It is demonstrated that no other reported cross sections are compatible with the experimental results used in the present derivation.

No abstract

Kinetic-energy distributions are presented for ions sampled from 13.56-MHz discharges in argon in a capacitively-coupled, parallel-plate, Gaseous Electronics Conference (GEC) radio-frequency reference cell. The cell was modified to allow sampling of ions through an orifice in the grounded electrode. Kinetic-energy distributions are presented for Ar+, Ar++, Ar+2, ArH+, and several trace ions for plasma pressures ranging from 1.3 Pa, where ion-atom collisions in the plasma sheath are not important, to 33.3 Pa, where collisions are important. Applied peak-to-peak radio-frequency (rf) voltages of 50, 100, and 200 V were used, and the current and voltage waveforms at the powered electrode were measured. Dependences of the ion fluxes, mean energies, and kinetic-energy distributions on gas pressure and applied rf voltage are interpreted in terms of possible ion-collision processes. The results agree with previously measured kinetic-energy distributions of ions sampled from the side of the plasma through a grounded probe for similar discharge conditions, verifying that ion kinetics are characteristic of the plasma sheath independent of where it is formed [J. K. Olthoff, R. J. Van Brunt, and S. B. Radovanov, J. Appl. Phys. 72, 4566 (1992)].

No abstract