Abstract
A combination of fast plasma diagnostics are utilized to probe the propagation of laser ablation plumes in vacuum and low-pressure background gases in order to understand key gas dynamic processes relevant to film growth by pulsed laser deposition. During expansion into low-pressure background gases, the ion flux in the plasma plume splits into fast and slow components over a limited range of distances and times. This general effect is presented here for the case of yttrium ablation into argon, a single-element target into an inert gas. Time-resolved optical absorption spectroscopy and optical emission spectroscopy are employed to simultaneously view the populations of both excited and ground states of Y and Y+ for comparison with intensified-CCD photography of the visible plume luminescence and ion flux measurements made with fast ion probes during this phenomenon. These measurements indicate that plume-splitting in background gases is consistent with momentum transfer from an initial, vacuum velocity distribution into a second, slowed velocity distribution initiated by scattering collisions between plume and background gas atoms. The fast distribution is exponentially attenuated in accordance with Beer's law, and the second, slowed distribution coalesces into a stable, propagating shock structure.
| Original language | English |
|---|---|
| Pages (from-to) | 15-25 |
| Number of pages | 11 |
| Journal | Proceedings of SPIE - The International Society for Optical Engineering |
| Volume | 2403 |
| DOIs | |
| State | Published - Apr 10 1995 |
| Event | Laser-Induced Thin Film Processing 1995 - San Jose, United States Duration: Feb 1 1995 → Feb 28 1995 |
Funding
The authors wish to acknowledge many helpful discussions with C.-L. Liu, K.-R. Chen, J.M. Donato, and R.F. Wood. The authors would also like to thank B.C. Sales and H. Harmon for their assistance in target preparation. This work was supported by the Division of Materials Sciences, U.S. Department of Energy under contract DE- The authors wish to acknowledge many helpful discussions with C.-L. Liu, K.-R. Chen, J.M. Donato, and R.F. Wood. The authors would also like to thank B.C. Sales and H. Harmon for their assistance in target preparation. This work was supported by the Division of Materials Sciences, U.S. Department of Energy under contract DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc. The submitted manuscript has been authored by a contractor of the U.S. Government under contract No. DE— ACO5-840R2 1400. Accordingly, the U.S.