Depth profiling: RBS versus energy-dispersive X-ray imaging using scanning transmission electron microscopy

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• 作者：Markwitz ; Andreas
• 关键词：85.40.R ; 85.60 ; 78.55 ; 61.46 ; RBS ; STEM ; Nanocluster ; Depth profiling ; Lateral resolution ; Photoluminescence
• 刊名：Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
• 出版年：2000
• 出版时间：March, 2000
• 年：2000
• 卷：161-163
• 期：Complete
• 页码：221-226
• 全文大小：227 K

文摘

Rutherford backscattering spectrometry (RBS) is known to be one of the techniques ideal for analysis of thin films. Elemental concentrations of matrix components and impurities can be investigated as well as depth profiles of almost each element of the periodic table. Best of all, RBS has both a high sensitivity and a high depth resolution, and is a non-destructive analysis technique that does not require specific sample preparation. Solid-state samples are mounted without preparation inside a high-vacuum analysis chamber. However, depth-related interpretation of elemental depth profiles requires the material density of the specimen and stopping power values to be taken into consideration. In many cases, these parameters can be estimated with sufficient precision. However, the assumed density can be inaccurate for depth scales in the nanometer range. For example, in the case of Ge nanoclusters in 500 nm thick SiO₂ layers, uncertainty is related to the actual position of a very thin Ge nanocluster band. Energy-dispersive X-ray emission (EDX) spectroscopy, using a high-resolution scanning transmission electron microscope (STEM) can assist in removing this uncertainty. By preparing a thin section of the specimen, EDX can be used to identify the position of the Ge nanocluster band very precisely, by correlating the Ge profile with the depth profiles of silicon and oxygen. However, extraction of the concentration profiles from STEM–EDX spectra is in general not straightforward. Therefore, a combination of the two very different analysis techniques is often the best and only successful way to extract high-resolution concentration profiles.