Species resolved analysis of the expansion of hydroxyapatite laser ablation plumes
- PDF / 168,475 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 111 Downloads / 149 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Species resolved analysis of the expansion of hydroxyapatite laser ablation plumes P. Serra and J. L. Morenza Departament de F´ısica Aplicada i Electr`onica, Universitat de Barcelona, Avda. Diagonal 647, E-08028 Barcelona, Spain (Received 1 February 1996; accepted 25 June 1997)
The plume generated by ablation of hydroxyapatite targets under ArF excimer laser irradiation has been investigated by means of fast intensified charge coupled device (CCD) imaging and optical emission spectroscopy. Results have shown that the plume splits into two plasma clouds as it expands. Time and spatial resolved spectra have revealed that under the experiment conditions emission is mostly due to calcium neutral atoms and calcium oxide molecular radicals. Imaging of the plume with the aid of bandpass filters has demonstrated that the emissive species in the larger and faster plasma cloud are calcium neutral atoms whereas in the smaller and slower one are calcium oxide molecular radicals.
Pulsed laser deposition (PLD) is a good technique to deposit thin films of complex compounds, and many authors1–6 have used it to obtain hydroxyapatite (HA) coatings for medical prostheses. This motivated us to study the HA laser ablation process through the characterization of the plume by fast intensified CCD imaging.7,8 The resultant pictures of the plasma generated by ArF excimer laser irradiation of HA targets revealed the presence of two different emissive regions. Thus, in this paper we develop a more comprehensive analysis of the HA laser ablation plume by means of time and space resolved optical emission spectroscopy in addition to fast intensified CCD imaging in order to characterize better the ablation process and to identify the nature of both regions. An ArF excimer laser (Lambda Physik LPX 205i) provides pulses at a wavelength of 193 nm, with duration of 23 ns, and energy of 300 mJ. The beam is limited by a 12 3 2 mm2 mask and impinges at an angle of 45± onto a pellet made from HA powder pressed at 6 3 108 Pa at room temperature. The fluence on the target is about 1.5 Jycm2 . All the experiments are carried out in a high vacuum chamber evacuated to a base pressure of 5 3 1025 mbar. Images are taken with a gated CCD camera (ANIMATER-VI from ARP France), 288 3 384 pixels, 8 bits dynamic range, intensified by a microchannel plate (MCP) whose aperture is delayed by a pulse generator triggered by a fast photodiode that is activated by the laser pulse. Bandpass filters (MicroCoatings Inc.) centered at 520 and 600 nm with a FWHM of 10 nm are also used in some of the recorded images and, in these cases, accumulations of 20 shots are needed to acquire an image. Otherwise, pictures are taken in a single shot mode. The optical emission spectra are acquired by means of a 0.5 m spectrometer (Chromex 500IS/SM). The 1132
http://journals.cambridge.org
J. Mater. Res., Vol. 13, No. 5, May 1998
Downloaded: 22 Mar 2015
laser-generated plume is imaged onto the entrance slit in such a way that the propagation
Data Loading...
