Ek M, Lehmann Sebastian, Wallenberg Reine
Centre for Analysis and Synthesis, Lund University, Box 124, Lund 22100, Sweden. NanoLund, Lund University, Box 118, Lund 22100, Sweden.
Nanotechnology. 2020 Sep 4;31(36):364005. doi: 10.1088/1361-6528/ab9679. Epub 2020 May 26.
Energy dispersive x-ray spectroscopy in a transmission electron microscope is often the first method employed to characterize the composition of nanowires. Ideally, it should be accurate and sensitive down to fractions of an atomic percent, and quantification results are often reported as such. However, one can often get substantial errors in accuracy even though the precision is high: for nanowires it is common for the quantified V/III atomic ratios to differ noticeably from 1. Here we analyse the origin of this systematic error in accuracy for quantification of the composition of III-V nanowires. By varying the electron illumination direction, we find electron channelling to be the primary cause, being responsible for errors in quantified V/III atomic ratio of 50%. Knowing the source of the systematic errors is required for applying appropriate corrections. Lastly, we show how channelling effects can provide information on the crystallographic position of dopants.
透射电子显微镜中的能量色散X射线光谱法通常是用于表征纳米线成分的首要方法。理想情况下，它应精确且灵敏至原子百分比的分数级别，并且定量结果也常如此报告。然而，即便精度很高，人们仍常常会在准确性上出现较大误差：对于纳米线而言，量化的V/III原子比明显不同于1是很常见的情况。在此，我们分析了在量化III-V族纳米线成分时准确性方面这种系统误差的来源。通过改变电子照射方向，我们发现电子通道效应是主要原因，它导致量化的V/III原子比出现50%的误差。要进行适当校正，就需要了解系统误差的来源。最后，我们展示了通道效应如何能够提供有关掺杂剂晶体学位置的信息。
