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Plasma properties suitable for pulsed laser deposition
Author
Zheng, Bangke
Supervisor
Lee, Paul Choon Keat
Abstract
Pulsed laser deposition is one of the important current applications of laser-produced plasmas. However, much of the physics work done with laser produced plasmas is in the field of inertial confinement fusion and x-ray lasers. In order to investigate plasma properties suitable for pulsed laser deposition, a 10Hz, 1064nm wavelength, Nd:YAG laser, with pulse energy of 0.17-0.45J, pulse duration of 5-14ns and laser spot radius of 50-400?m was used to ablate graphite targets. Faraday cups placed at different angles with respect to the normal and different distances from the target surface were used to measure the ion distribution. The experimental results show that when laser irradiation intensity increases, ion average energy, ion maximum energy, ion flux, ion energy flux and ion temperature increase. When the laser spot size is larger, the ion emission concentrates more closely to the target normal direction; ion maximum energy and ion average energy in higher. The ion flux and ion energy flux decrease with the increase of the distance from the target. For laser irradiation intensity of 1.6-6.6x1012 W/cm2 and base pressure 1.1x10-5 mbar, 6.8x1013 - 2.0x1014 ions reach 5 cm from the laser focal spot with a total energy of 1.2x10-5 - 3.6x10-3J. Ion temperature is 1.4-28 eV. Ion average energy is 1.2-1.4 eV. Maximum ion energy is about 9.4x102 eV. The laser-induced plasma was simulated using the MEDUSA program. The refractive indexes of the films deposited at different laser irradiation intensity were measured by determining Brewster angle. The thickness of the film was measured using a micro-interferometer. These results allow us to understand how various setups could be used to obtain certain types of films and also the deficiencies in MEDUSA.
Date Issued
2002
Call Number
QC718.5.L3 Zhe
Date Submitted
2002