Ultrafast Dynamics Of Phase Transitions Of Ge <sub> 2 </ Sub> Thin Film Materials Of Sb <sub> 2 </ Sub> Te <sub> 5 </ Sub>

The transformation properties and ultrafast dynamics of Phase-change material (GST) film were studied in this paper by femtosecond laser irradiation and pump-probe technique. The optical principle of pump-probe technique and the Phase-transformation mechanism of GST caused by femtosecond laser irradiation were introduced in article.The samples were prepared by Multi-targets sputtering apparatus made in the German Leybold company. Ge2Sb2Te5 compound target were accumulate on high purity silicon (better than 99.99%) substrate. X-ray diffraction analysis, Raman scattering spectrometry (LRS), Optical microscopy were used to detect the transformer and it's surface morphology of GST caused by femtosecond laser irradiation. The carrier dynamics of GST thin films in the process were observed with the help of pump-probe technique.The theory of the research were introduced first.1,The carrier dynamics caused by laser pulse in the time scale of femtosecond to millisecond;2,The applications of femtosecond laser in study of phase-change field and some technique in ultra fast research.3,The principle and applications in micro-dynamics research of pump-probe technique.4,The applications of GST phase-change material in optical storage.Secondly, the experiment and research method were described in this article. The femtosecond laser pulse(center wavelength is 800nm, pulse width is 10Ofs, frequency is 1kHz, the average power is 1OmW) were used to irradiate the samples. The transformer from amorphous state to crystalline state were detected by Raman spectroscopy and X-ray diffraction analysis. Microscope showed that the shape of the area irradiated by laser pulse are inerratic and clear. The carrier dynamic in transformation process were detected by pump-probe technique.Finally, the explanation of the transformation of GST film caused by laser irradiation and the idea for further research are given.The concentration of the research are in terms of:1,The construction of pump-probe system; 2,The carrier dynamics within femtosecond of GST films were studied. The irradiation under a lower laser pulse can pump the samples and the reflectivity's change were used to learn it's carrier dynamics.Secondly, through the analysis to the laser irradiate area, and comparison with temperature annealing samples, we can get the difference of the two dealings. The two dealings with different mechanisms, lead to the same result.