SEM-EDX Analysis of Insulator Specimens by Diluted Ionic Liquid -Application to Volcanic Particles-

Abstract

Ethanol diluted (1 wt %) ionic liquid 1-ethyl-3-methylimidazolium acetate is used in order to avoid the charge-up of insulator specimen for scanning electron microscope (SEM) analysis. SEM-EDX analysis is additionally performed for the specimen treated by the ethanol diluted ionic liquid. As an example of the insulator specimen, we analyze volcanic ash particles, and succeed to discriminate the elemental composition difference of a specimen surface within 10 μm2 micro area. Though a clear secondary electron image of the volcanic ash particle of which diameter is less than 10 μm can be obtained without electric conductive treatment, particles of diameter larger than 20 μm are needed to be treated by the diluted ionic liquid to avoid the charge-up effects.

エタノールで1 wt％ に希釈した1-ethyl-3-methylimidazolium acetateを絶縁性試料の走査型電子顕微鏡（SEM）観察における帯電防止剤として用いた．その上で，微小領域における元素分析をエネルギー分散型X 線分析（EDX）で行った．絶縁性試料として火山灰を用いたところ，従来の炭素薄膜を蒸着する帯電防止法と同様に10 μm2の微 小領域で粒子の元素組成の違いを判別することができた．また，粒子径が10 μm以下の火山灰については帯電防止処理を行わなくても鮮明な二次電子像が得られたが，粒子径が20 μm以上の火山灰については鮮明な二次電子像を得るためには帯電防止処理が必要であることが分かった.