ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The transport of ions through rf glow-discharge sheaths was simulated with a Monte Carlo method to determine the distributions of ion-bombardment energy and angle of impact. Several sheath parameters were varied and their effects examined: (1) the type of ion-molecule scattering (hard sphere, potential field interaction, charge exchange), (2) the ratio of ion and neutral masses, (3) the ratio of the sheath width to collision mean free path, (4) spatially uniform, spatially linear, and time-dependent (rf) electric fields in the sheath, and (5) the frequency of an rf component in the sheath. The results of the Monte Carlo simulations indicate that the type of elastic scattering (hard sphere or soft sphere) does not significantly change either the impact angle distributions or the scaled ion-bombardment energy distributions. Charge-exchange scattering produces a much greater ion-bombardment directionality and a different shape of the ion-bombardment energy distribution. The fully developed distributions depend only on the ion-to-neutral mass ratio, type of ion-neutral scattering, and the dc value of the electric field-to-pressure ratio at the electrode. Fully developed distributions are reached in approximately three mean free paths in spatially uniform sheath fields and in about six mean free paths for spatially linear sheath fields. The minimum ion directionality was observed when the ion-to-molecule mass ratio was approximately unity. Time-dependent (rf) variation of the sheath field produces features in the ion energy distributions which are similar for both the collisional and collisionless sheaths.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.341062
