基于同轴电子全息定量表征水环境中Pd颗粒的荷电效应

汪雨轩,任天星,于洪杨,张婉如,田 鹤*,李吉学,张 泽

基于同轴电子全息定量表征水环境中Pd颗粒的荷电效应

汪雨轩,任天星,于洪杨,张婉如,田  鹤*,李吉学,张  泽

(浙江大学电子显微镜中心,硅材料国家重点实验室,材料科学与工程学院,浙江 杭州 310027)

摘  要 纳米尺度上的电荷分布表征一直充满挑战,因为纳米结构中往往电荷量极低且易受外场影响而变化。例如:电子束辐照下样品会因荷电效应产生电荷积累,进而表现出不同的物理性质并干扰样品的表征结果。由于荷电效应积累的电荷量微小难以测量,对荷电效应的研究大多停留在定性分析层面。本文通过同轴电子全息的方法,定量表征了Pd颗粒及周围水环境受电子束辐照产生的荷电效应,并分析了不同束流密度下荷电效应对电荷密度与电荷量的影响。实验结果表明,低束流密度下,荷电效应不会导致Pd颗粒及周围水环境中产生明显的电荷积累;束流密度增大时,Pd颗粒呈负电,而周围水层表现为正电;并且随着束流密度增大,积累的正负电荷密度也随之增大。实验研究了荷电效应产生的电荷积累现象,从定量角度揭示了荷电效应对样品的影响,为排除荷电效应引入的非本征电荷提供了指导。并且同轴电子全息不但对实验条件高普适性,更展现出对电荷分布的高精度高灵敏度表征能力。

关键词 同轴电子全息;电荷分布表征;电子束辐照;荷电效应

中图分类号: 文献标识码:A  doi:10.3969/j.issn.1000-6281.2021.04.004

 

Characterization of charging effect of Pd particles in liquid environment by in-line electron holography

WANG Yu-xuan,REN Tian-xing,YU Hong-yang,ZHANG Wan-ru,TIAN He*,LI Ji-xue,ZHANG Ze

(1. Center of Electron Microscope, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou Zhejiang 310027,China)

Abstract  The characterization of charge distribution on the nanoscale has been challenging because the amount of charges in nanostructures is very low and easily affected by the external field. For example, under electron beam irradiation, the sample will generate charge accumulation due to charging effect, and then show different physical properties and interfere with the characterization results of the sample. Due to the small amount of charges accumulated by the charging effect, the research on the charging effect mostly stays at the level of qualitative analysis. In this paper, the charge effect of Pd particles and its surrounding water environment irradiated by electron beam is quantitatively characterized by in-line electron holography, and the influence of the charge effect on charge density and charge quantity under different beam densities is analyzed. The experimental results show that the charging effect will not lead to obvious charge accumulation in the Pd particles and the surrounding water environment at low beam density; when the beam density increases, the Pd particles are negatively charged, while the surrounding water layer is positively charged; and with the increase in beam density, the accumulated positive and negative charge density also increases. The charge accumulation caused by charging effect is studied experimentally, and the influence of charging effect on samples is revealed quantitatively, which provides guidance for eliminating the extrinsic charges introduced by charging effect. In addition, the in-line electron holography is not only universal to the experimental conditions, but also shows the ability to characterize the charge distribution with high accuracy and sensitivity.

Keywords  in-line electron holography;charge distribution characterization; electron beam irradiation; charging effect

 

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