Study On Preparation With PLD Method And Properties Of Amorphous GeS₂-Ga₂S₃-CdS Film

Era of information has come, the overwhelmingly increased quantity of information brought in the need of converting contemporary electronic or electrooptical communication into all-optical communication. However, it is the problem of how to exploit nonlinear materials, especially second-order nonlinear materials with prior optical properties that obstacles the further development of all-optical communication. Endowed with priorities of low phonon energy,high refractive index,being easy to be prepared and processed,big second-order nonlinear susceptibility, etc, chalcogenide glasses have been ranked as a kind of second-order optical material with many potential applications. Nevertheless, it still leaves a long way to go when it refers to practical application because of difficulties existing in preparation of bulk with size big enough. PLD(pulsed laser deposition)method possesses a lot of unique priorities compared with others when applied on deposition of inorganic amorphous thin films, for example, it demand little on the target, it can keep small discrepancy of composition between the film and the target, besides, films prepared by this method always have nice properties. If made into film with PLD method, the chalcogenide glass will both keep its excellent optical properties and expand its functional acreage in that the area of film can be much larger than the one of bulky glass, consequently, will realize its practical usage. Compared with bulky glass, film has smaller thickness, which makes it be easier to be polarized, alongside with the trend of making optical devices into film, it is very necessary and significant to study the processing of chalcogenide glassy film.In this paper, using conventional fusing-quenching method, bulky glass with composition of 90GeS₂·5Ga₂S₃·5CdS was prepared, which was subsequently used as target for PLD. With PLD method, we deposited chalcogenide film and characterized it with XRD(X-Ray diffraction),Transmittance test,SEM(Scanning electronic microscopic),Raman Spectra,XPS(X-ray photoelectron spectroscopy). Characterization results indicated that the as-prepared film was amorphous, of homogeneous and packed texture, its thickness reached to 800 nanometers with a short-cut wavelength placed at about 447nm while its average transmittance was higher than 75%; compared with the target, the structures of the film differed little, being mainly [GeS_4/2],[GaS_4/2] tetrahedral and its composition was a little discrepant, but not so obvious.The polarization methods here were respectively 355nm-wavelength ultraviolet pulsed laser polarization(UV-pulsed laser polarization),electron beam bombarding and electrical-thermal field polarization. After polarization, characterization including Maker fringes test,transmittance measurement,Raman spectra were done to the samples. From the results of Maker fringes test, obvious second-harmonic generation could be seen. The UV-pulsed laser polarization was the most effective method of the three, the biggest second-order nonlinear susceptibility obtained with it was nearly 23pm/V while the ones obtained by the other two were respectively 7.38pm/V and 3.82pm/V. Variation trends of second-order nonlinear susceptibility along with polarization parameters of the three methods were very alike:UV-pulsed laser polarization, x² increased with the illuminating time lengthened and the single pulse energy increasing; electron beam bombarding, x² became bigger as the accelerating voltage went higher and the bombarding time lasted longer; electrical-thermal field, x² went higher companied by the polarizing voltage and temperature enhanced.The writer compared these three methods on three aspects: functioning area,polarization effect and SHG mechanism. It was found that both likeness and discrepancy existing among these three methods. Limited by the relative small diameter of the laser or electron beam, UV-pulsed laser polarization and electron beam bombarding could be applied only on a local part of the samples, while electrical-thermal polarization was able to cover a whole sample. When it referred to the polarizing effect, these three ones could be ranked as UV-pulsed laser polarization,electron beam bombarding and electrical-thermal polarization in a declining sequence. The writer held the opinion that SHG mechanism of UV-pulsed laser polarization and electron beam bombarding should be related to activity of electron from atoms of the film body and the incident electron beam, and the one of electrical-thermal polarization perhaps originated from uniform orientation of dipoles in film body compelled by exterior strong field.