Pulse Energy Dependence of Spectral Characterization Using Laser-induced Plasma for Quantitative Analysis of Indium-Tin-Oxide (ITO) Film
Laser-induced breakdown spectroscopy (LIBS) is a promising technique for in situ analysis. The relationship between the signal intensity and the pulse energy of a Nd:YAG laser beam was investigated for indiumtin- oxide (ITO). It was found that the signal of the analysed lines of In and Sn increased with the laser energy in a proportional fashion. Due to the ionic energy of In (5.786 eV) being much lower than that for the Sn (7.3439 eV), so the degree of intensity enhancement of the In lines (325.609, 410.177 and 451.131 nm) were much larger than that for the Sn lines (283.999, 286.333,317.502 and 326.234 nm). By a series of measurements we found the optimum time delay between the laser pulse and the beginning of the LIBS spectra acquisition was about 2 to 4 μs. Finally, through calibration-free method we obtain the temperature of plasma was about 5400 K when the pulse energy was 20 mJ. At the same time we measured the content of In and Sn to be approximately 30 and 32%, respectively, by a program written with Matlab.
Keywords: Laser-induced breakdown spectroscopy (LIBS), indium-tin-oxide (ITO), Nd:YAG laser, quantitative analysis, plasma temperature