Influence of Ar buffer gas on the LIBS signal of thin CIGS films

Abstract

Laser induced breakdown spectroscopy (LIBS) measurement of a thin Cu(In,Ga)Se₂ (CIGS) absorber layer was performed under the conditions of open air and argon (Ar) gas jet flow (25 L min⁻¹). A second harmonic Q-switched Nd:YAG laser (λ = 532 nm, τ = 5 ns, top-hat profile) was employed for the ablation of co-evaporated CIGS samples. The use of an Ar gas jet for the LIBS measurement of CIGS thin films leads to two significant differences from the open air measurement results that are important from the precision point of view: (i) the increase of signal intensity and (ii) decrease of relative standard deviation (RSD) of measured intensity or intensity ratios. From calculation of the degree of intensity enhancement, it was shown that the enhancement of signal intensity is primarily due to the increase of plasma temperature and electron density under Ar buffer gas environment. It was also found that in addition to the influence of Ar gas itself the gasdynamic effects of the Ar gas jet contribute significantly to the reduction of RSD.