Property improvement of pulsed laser deposited boron carbide films by pulse shortening |
| |
Authors: | T Csákó T Szörényi |
| |
Institution: | a Department of Optics and Quantum Electronics, University of Szeged, P.O. Box 406, H-6701 Szeged, Hungary b Research Group on Laser Physics of the Hungarian Academy of Sciences, University of Szeged, P.O. Box 406, H-6701 Szeged, Hungary |
| |
Abstract: | Growth characteristics and surface morphology of boron carbide films fabricated by ablating a B4C target in high vacuum with a traditional KrF excimer laser and a high brightness hybrid dye/excimer laser system emitting at the same wavelength while delivering 700 fs pulses are compared. The ultrashort pulse processing is highly effective. Energy densities between 0.25 and 2 J cm−2 result in apparent growth rates ranging from 0.017 to 0.085 nm/pulse. Ablation with nanosecond pulses of one order of magnitude higher energy densities yields smaller growth rates, the figures increase from 0.002 to 0.016 nm/pulse within the 2-14.3 J cm−2 fluence window. 2D thickness maps derived from variable angle spectroscopic ellipsometry reveal that, when ablating with sub-ps pulses, the spot size rather than the energy density determines both the deposition rate and the angular distribution of film material. Pulse shortening leads to significant improvement in surface morphology, as well. While droplets with number densities ranging from 1 × 104 to 7 × 104 mm−2 deteriorate the surface of the films deposited by the KrF excimer laser, sub-ps pulses produce practically droplet-free films. The absence of droplets has also a beneficial effect on the stoichiometry and homogeneity of the films fabricated by ultrashort pulses. |
| |
Keywords: | PLD Thin films Thickness distribution Ultrashort pulse processing Surface morphology Nanostructure |
本文献已被 ScienceDirect 等数据库收录! |
|