講座

プラズマと分光分析
V．分光学的方法によるプラズマ診断

Plasma and Spectroscopic Analysis
V. Plasma diagnostics by spectroscopic methods

佐々木　浩一
Koichi SASAKI

本稿は，分光学的方法を用いたプラズマ診断技術についての網羅的解説であり，特に，材料プロセシングで用いられる反応性プラズマ中のラジカル密度を測定する方法について重点的に説明する。分光学的プラズマ診断法を，簡便・安価な発光分光法(受動分光法)とより信頼性の高い能動分光法に分け，それぞれの基礎について簡潔に述べる。また，実際に反応性プラズマ中のラジカル密度測定に用いられているいくつかのプラズマ診断技術について例を挙げて説明する。

Plasma diagnostics by spectroscopic methods are reviewed with the emphasis on measurements of radical densities in reactive plasmas used for material processing. A brief introduction on the radiation equilibrium of plasmas will be given on the basis of a collisional-radiative model. Optical emission spectroscopy (OES) is an economical diagnostic method, but simple OES is not useful for estimating radical densities. An improved OES method is actinometry, which is widely used in reactive plasma experiments. Active spectroscopic methods such as absorption spectroscopy and laser-induced fluorescence are more reliable for measuring radical densities. Various types of absorption spectroscopy using various light sources will be introduced after a brief description of the fundamentals of optical absorption. The advantages of laser-induced fluorescence are the compatibility with imaging spectroscopy and the applicability to measurements of various quantities in plasmas.

Keywords: Collisional-radiative model, Optical emission spectroscopy, Actinometry, Absorption spectroscopy, Laser-induced fluorescence