Effective approaches for realizing quantitative analyses and high lateral resolution images on highly insulating samples by Auger electron spectroscopy

Abstract

The analysis of insulating materials by Auger electron spectroscopy (AES) remains difficult to achieve because of the accumulation of charges in the sample. Residual charges trapped in the specimen can lead to numerous spectra modifications such as an energy shift of the Auger transitions, enlargement, splitting and deformation of the peaks, intense or lack of secondary and Auger electrons emission.Among the different approaches already developed to circumvent this issue, two of them were considered in this study to carry out AES experiments on a SiAlON insulating ceramic: the charge compensation method and the thin film method. For both of these methods, a systematic approach was used, combining a specific sample preparation with optimized analytical settings to mitigate the charge effects to enable quantitative analysis and high lateral resolution images.The charge compensation method, dedicated to bulk samples, is based on the control of the total secondary electron yield (TSEY) during analysis by optimizing the intensity, the energy and the incident angle of the primary electron beam. Its combination with the metallization of the surface sample and the use of low energy Ar+ ions to compensate the charges allowed the determination of the elemental composition of the three sub-micrometric phases of the ceramic. High lateral resolution (70nm) Auger maps were also acquired, demonstrating therefore the long-time stability of the surface charge during acquisitions even for small analysis areas. A second method, consisting in thinning the sample down to less than a hundred of nanometres and analyzing it with a high energy electron beam, was implemented too. The results (quantification and imaging) are in good agreement with the analysis of the sample as a bulk.