Laser-Induced Growth of In-Sb-Se Thin Films
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LASER - INDUCED GROWTH OF In-Sb-Se THIN FILMS
K. KOLEV* and L.D. LAUDE** * Bulgarian Academy of Sciences, Central Laboratory of Photograf. Processes, Sofia, Bulgaria ** University of Mons-Hainaut, Department of Materials, Mons, Belgium ABSTRACT Three-elements (In-Sb-Se) sized by laser irradiation of
alloy thin films are synthemulti-layered films. Optical characterization of the films is performed function of laser fluence which helps defining optimized conditions for the production of good quality, homogeneous alloy films. Such films exhibit particularly high reflectiviy contrast (4:1) for the alloy SeSb2.25 In 1 . 7 5 . INTRODUCTION Laser-induced synthesis (L.I.S.) of binary and ternary alloys and semiconducting compounds is a promising new alternative for producing thin films compatible with optoelectronic, photovoltaic and optical data storage applications [1-8]. Laser-induced alloy formation in the In-Sb-Se atomic system is a particular challenge because it is well known that this system is promising as a recording material for erasable disks
[9). In this contribution we summarize the results of our investigation in laser-assisted growth of thin films of In-SbSe. Even though the precise mechanisms, thermodynamics and details of the process are not clear, it is certain that ternary alloy thin film of reasonably good quality can be succesfully fabricated by intermixing the constituent elements either by melting or by diffusion with laser radiation. EXPERIMENTAL Thin films of In, Sb and Se are successively deposited onto glass substrates by electron gun thermal evaporation in vacuum better than 1O- 5Pa. The substrates are first ultrasonically and glow-discharge cleaned 1 mm thick microscope glass plates. The individual layer thickness is controled by a Mat. Res. Soc. Symp. Proc. Vol. 201. c 1991 Materials Research Society
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vibrating quartz monitor in order to ensure different stoichiometric ratio between elements. Typical film thicknesses were about 100 nm. Relative atomic proportions of such layered films are varied in the range 20 to 45 % for each element. Different deposition sequences of tituents have also been investigated. The layer system was irradiated in air by a
the three -consobtained threeCW-Ar-ion laser (Spectra Physics Model 171) operating on all green lines (488-514 nm) . The spatial profile of the beam is Gaussian, with a diameter (l/e 2) at the sample of 1.6 mm. The change of reflectivity of the film at the center of the irradiated zone is measured during irradiation by recording the output signal of a photodiode which collects the reflected light of a He-Ne laser at an incidence angle of a few degrees to the center of the irradiated zone. This time-resolved reflectivity measurement is used to determine the kinetics of the phase formation at fixed Ar-ion laser power values, P. Transformed surfaces of about 1 cm 2 in extend were obtained by scanning the laser beam with a rotating mirror (scanning speed 2 mm/ sec) and focusing it on the sample with a cylindrical lens. The overlapping of su
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