Pulsed CO₂ laser-induced gas plasma spectroscopy based on single beam splitting for trace metal analysis on a material surface

ABSTRACT

Laser-induced gas plasma spectroscopy based on pulsed CO₂ laser beam splitting has been applied to the problem of trace film analysis on the silicon surface. In this study, 2.1 J of laser energy (70% of the laser beam) was focused at a 10-degree incidence on a metal mesh attached to a sample surface containing trace metal elements in order to produce a gas plasma. The remaining part of the laser beam (approximately 30% or 0.9 J) was employed to vaporize a film which had been deposited on the material by focusing the laser beam 3 cm under the surface. In this scheme, the vaporized metal film moves into the gas plasma region, in which the dissociation and excitation takes place. Our measurements show that the detection of Cr on the silicon surface can be made with high sensitivity. The limit of detection of Cr in the silicon material was approximately 7.5 × 10¹² atom/cm².

KEYWORDS:

• Silicon surface analysis
• laser-induced plasma spectroscopy
• laser-induced gas plasma spectroscopy
• single beam splitting method

Acknowledgements

This study includes a research project scheme for international publication in high-reputation international journal in 2018 supported by Diponegoro University, Indonesia (474-112/UN7.P4.3/PP/2018). Special thanks to Mr Yasuhiro Yamakage, Mr Takashi Ohno and Mr Masahiro Ihara for their kind support, critical suggestions and scientific discussion.

Disclosure statement

No potential conflict of interest was reported by the authors.