场发射扫描电子显微镜观测弱导电金属有机框架材料的参数探究

邢宏娜; 常帅; 冯伟; 李兴华

doi:10.16495/j.1006-3757.2023.02.004

场发射扫描电子显微镜观测弱导电金属有机框架材料的参数探究

doi: 10.16495/j.1006-3757.2023.02.004

西北大学物理学院，陕西西安　710127

基金项目: 国家自然科学基金资助项目（11504293）

详细信息

作者简介:
邢宏娜（1995−），女，硕士，工程师，主要从事电子显微镜的测试管理，E-mail：hongnxing@nwu.edu.cn

通讯作者:
李兴华(1986−)，男，博士，教授，从事大型仪器管理和微波吸收、能源存储领域科学研究，E-mail：lixinghua04@gmail.com

中图分类号: O657; O762
计量
- 文章访问数: 91
- HTML全文浏览量: 16
- PDF下载量: 12
- 被引次数: 0
出版历程
- 收稿日期: 2022-12-16
- 录用日期: 2023-04-13
- 修回日期: 2023-04-13
- 刊出日期: 2023-06-30

Exploration of Test Parameters for Weakly Conductive Metal-Organic Framework Materials by Field Emission Scanning Electron Microscopy

School of Physics, Northwest University, Xi’an 710127, China

Funds: National Natural Science Foundation of China (11504293)

摘要

摘要: 金属有机框架材料（MOFs）的形貌结构对其性能应用具有很大影响，但MOFs普遍存在导电性差且对电子束敏感等问题，在进行扫描电子显微镜（SEM）测试时容易损伤样品，发生荷电现象. 因此摸索合适的测试参数，对获得高质量的MOFs扫描电子显微镜图像具有重要意义. 以MIL-101(Cr)、Fe-MOF、Mn-MOF、ZIF-67(Co)这4种典型的MOFs为例，主要探究了加速电压、电子束流、工作距离、探头及喷金对其成像效果的影响. 结果表明，升高加速电压可有效提高图像分辨率，但同时电子束穿入深度增大，可能导致电荷击穿效应对其表面结构造成破坏. 适当增大束流可提高图像信噪比，但过大的束流会导致纳米颗粒边缘变钝，因此选用0.1~0.4 nA中等束流为佳. 在选择探头时需注意，艾弗哈特-索恩利探头（ETD）和透镜内二次电子（T2）探头所成图像立体感较好，透镜内背散射电子（T1）探头的立体感弱，但衬度较好，柱内二次电子（T3）探头分辨率最佳，但更容易荷电，显得颗粒扁平. 而喷金处理可有效提高样品的导电性. 以上结果对使用SEM探究MOFs形貌结构具有一定的借鉴作用.
- 场发射扫描电子显微镜 /
- 金属有机框架材料 /
- 荷电效应 /
- 图像分辨率
Abstract: The morphology and structure of metal-organic frameworks (MOFs) have a significant impact on their performance and application. However, MOFs generally have poor electrical conductivity and are sensitive to electron beams, which can be easily damaged and appear charge phenomena during the scanning electron microscopic (SEM) testing. Therefore, it is of great significance to explore the proper test parameters to obtain high-quality SEM images of MOFs. Taking MIL-101 (Cr), Fe-MOF, Mn-MOF and ZIF-67(Co) as examples, the effects of acceleration voltage, beam current, working distance, probe and gold spray on SEM images were investigated. The results showed that the increase of the acceleration voltage can effectively improve the image resolution, but at the same time the penetration depth of electron beam also increased, which may lead to the charge breakdown effect and damage to the surface structure. A moderate increase of the beam current can improve the signal-to-noise ratio of the image, but too large a beam current will cause an indistinct edge of nanoparticles, so a medium beam current of 0.1~0.4 nA was preferred. As to the selection of the probe, it should be noted that on the Everhart-Thornley detector (ETD) and in-lens secondary electrons detector (T2) a good stereoscopic perception can be obtained on the in-lens backscattered electrons detector (T1) a poor three-dimensional sense can be obtained, but the contrast is better. The best resolution can be obtained on the in-column secondary electrons detector (T3) , but is more easily charged and appears to have flat particles. The gold spraying treatment can effectively improve the conductivity of the samples. These above results are helpful to explore the morphology of MOFs by SEM.
- field emission scanning electron microscope /
- MOFs /
- charging effect /
- image resolution

HTML全文

图 1 不同加速电压下MIL-101(Cr)的SEM图像

（a）3 kV，（b）5 kV，（c）8 kV，（d）10 kV，（e）15 kV，（f）20 kV，（g）30 kV，（h）加速电压与图像分辨率的关系曲线图

Figure 1. SEM images of MIL-101(Cr) at different accelerating voltages

(a) 3 kV, (b) 5 kV, (c) 8 kV, (d) 10 kV, (e) 15 kV, (f) 20 kV, (g) 30 kV, (h) relationship curve between acceleration voltage and image resolution

下载: 全尺寸图片幻灯片

图 2 MIL-101(Cr)的SEM图像

（a）~（d）加速电压为8 kV，不同束流6.0（25 pA）、8.0（0.1 nA）、10.0（0.4 nA）、12.0（1.6 nA），（e）~（h）不同工作距离6、8、10、12 mm，（i）~（k）不同扫描探头T1、T2、T3，（l）喷金处理（20 s）

Figure 2. SEM images of MIL-101(Cr)

(a)~(d) accelerating voltages: 8 kV, different spot sizes: 6.0 (25 pA), 8.0 (0.1 nA), 10.0 (0.4 nA), 12.0 (1.6 nA), (e)~(h) different working distances: 6, 8, 10, 12 mm, (i)~(k) different detectors: T1, T2, T3, (l) after spraying gold treatment (20 s)

下载: 全尺寸图片幻灯片

图 3 不同加速电压下Fe-MOF的SEM图像

（a）3 kV，（b）5 kV，（c）8 kV，（d）10 kV，（e）15 kV，（f）20 kV，（g）30 kV，（h）加速电压与图像分辨率的关系曲线图

Figure 3. SEM images of Fe-MOF at different accelerating voltages

(a) 3 kV, (b) 5 kV, (c) 8 kV, (d) 10 kV, (e) 15 kV, (f) 20 kV, (g) 30 kV, (h) relation curve between acceleration voltage and image resolution

下载: 全尺寸图片幻灯片

图 4 Fe-MOF的SEM图像

（a）~（d）加速电压为8 kV，不同束流6.0（25 pA）、8.0（0.1 nA）、10.0（0.4 nA）、12.0（1.6 nA），（e）~（h）不同工作距离6、8、10、12 mm，（i）~（k）不同扫描探头T1、T2、T3，（l）喷金处理（20 s）

Figure 4. SEM images of Fe-MOF

(a)~(d) accelerating voltages: 8 kV, different spot sizes: 6.0 (25 pA), 8.0 (0.1 nA), 10.0 (0.4 nA), 12.0 (1.6 nA), (e)~(h) different working distances: 6, 8, 10, 12 mm, (i)~(k) different detectors: T1, T2, T3, (l) after spraying gold treatment (20 s)

下载: 全尺寸图片幻灯片

图 5 不同加速电压下Mn-MOF的SEM图像

（a）3 kV，（b）5 kV，（c）8 kV，（d）10 kV，（e）15 kV，（f）20 kV，（g）30 kV，（h）加速电压与图像分辨率的关系曲线图

Figure 5. SEM images of Mn-MOF at different accelerating voltages

(a) 3 kV, (b) 5 kV, (c) 8 kV, (d) 10 kV, (e) 15 kV, (f) 20 kV, (g) 30 kV, (h) relation curve between acceleration voltage and image resolution

下载: 全尺寸图片幻灯片

图 6 Mn-MOF的SEM图像

（a）~（d）加速电压为8 kV，不同束流6.0（25 pA）、8.0（0.1 nA）、10.0（0.4 nA）、12.0（1.6 nA），（e）~（h）不同工作距离6、8、10、12 mm，（i）~（k）不同扫描探头T1、T2、T3，（l）喷金处理（20 s）

Figure 6. SEM images of Mn-MOF

(a)~(d) accelerating voltages: 8 kV, different spot sizes: 6.0 (25 pA), 8.0 (0.1 nA), 10.0 (0.4 nA), 12.0 (1.6 nA), (e)~(h) different working distances: 6, 8, 10, 12 mm, (i)~(k) different detectors: T1, T2, T3, (l) after spraying gold treatment (20 s)

下载: 全尺寸图片幻灯片

图 7 不同加速电压下ZIF-67(Co)的SEM图像

（a）3 kV，（b）5 kV，（c）8 kV，（d）10 kV，（e）15 kV，（f）20 kV，（g）30 kV,（h）加速电压与图像分辨率的关系曲线图

Figure 7. SEM images of ZIF-67(Co) at different accelerating voltages

(a) 3 kV, (b) 5 kV, (c) 8 kV, (d) 10 kV, (e) 15 kV, (f) 20 kV, (g) 30 kV, (h) relation curve between acceleration voltage and image resolution

下载: 全尺寸图片幻灯片

图 8 ZIF-67(Co)的SEM图像

（a）~（d）加速电压为8 kV，不同束流6.0（25 pA）、8.0（0.1 nA）、10.0（0.4 nA）、12.0（1.6 nA），（e）~（h）不同工作距离6、8、10、12 mm，（i）~（k）不同扫描探头T1、T2、T3，（l）喷金处理（20 s）

Figure 8. SEM images of ZIF-67(Co)

(a)~(d) accelerating voltages: 8 kV , different spot sizes: 6.0 (25 pA), 8.0 (0.1 nA), 10.0 (0.4 nA), 12.0 (1.6 nA), (e)~(h) different working distances: 6, 8, 10, 12 mm, (i)~(k) different detectors: T1, T2, T3, (l) after spraying gold treatment (20 s)

下载: 全尺寸图片幻灯片

参考文献(21)

[1]	Ma Y H, Zhang X H, Chen X G. Observation on non-conductive powder samples by scanning electron microscope[J]. Applied Mechanics and Materials,2013,320 :226-229. doi: 10.4028/www.scientific.net/AMM.320.226
[2]	陈佳阳, 陈耀文. 蔡司GeminiSEM 300型场发射扫描电镜常见故障的预防、排除和磁性样品的测试方法[J]. 电子显微学报,2020,39(4):423-425 doi: 10.3969/j.issn.1000-6281.2020.04.013 CHEN Jiayang, CHEN Yaowen. Precaution and elimination of common faults in Zeiss GeminiSEM300 field emission scanning electron microscope and the test methods for magnetic specimens[J]. Journal of Chinese Electron Microscopy Society,2020,39 (4):423-425. doi: 10.3969/j.issn.1000-6281.2020.04.013
[3]	高翔, 朱紫瑞, 孙伟, 等. 场发射扫描电镜荷电现象的研究及参数优化[J]. 真空科学与技术学报,2018,38(11):1008-1012 doi: 10.13922/j.cnki.cjovst.2018.11.16 GAO Xiang, ZHU Zirui, SUN Wei, et al. Solutions to charge accumulation on low conductivity surfaces in imaging with scanning electron microscopy[J]. Chinese Journal of Vacuum Science and Technology,2018,38 (11):1008-1012. doi: 10.13922/j.cnki.cjovst.2018.11.16
[4]	彭宇, 张之恒, 安婷, 等. 导电环氧树脂消除扫描电子显微镜图像荷电问题的原理与实践[J]. 分析测试技术与仪器,2022,28(2):125-131 doi: 10.16495/j.1006-3757.2022.02.003 PENG Yu, ZHANG Zhiheng, AN Ting, et al. Principle and practice of conductive epoxy resin to eliminate charging problem in scanning electron microscope images[J]. Analysis and Testing Technology and Instruments,2022,28 (2):125-131. doi: 10.16495/j.1006-3757.2022.02.003
[5]	Wen Q, Ding Z, Kou F J, et al. Research and application of S-4800 scanning electron microscope in modern testing and analysis technology[J]. Applied Mechanics & Materials,2014 (668-669):936-939.
[6]	徐国荣, 黄琳, 丁宏刚, 等. 燃煤超细颗粒物的扫描电镜图像优化方法[J]. 中国测试,2022,48(2):113-117, 153 XU Guorong, HUANG Lin, DING Honggang, et al. SEM image optimization method of coal-fired ultrafine particles[J]. China Measurement & Test,2022,48 (2):113-117, 153.
[7]	赵素玲, 兰芳, 陈晶. 场发射扫描电镜研究实验条件对片形Fe@Ag复合粒子表面形貌的影响[J]. 分析仪器,2013(4):74-78 ZHAO Suling, LAN Fang, CHEN Jing. Influence of experimental conditions on the surface morphology of Fe@Ag core-shell composite particles[J]. Analytical Instrumentation,2013 (4):74-78.
[8]	Zhang Z C, Chen Y F, Xu X B, et al. Well-defined metal-organic framework hollow nanocages[J]. Angewandte Chemie (International Ed in English),2014,53 (2):429-433. doi: 10.1002/anie.201308589
[9]	Wang L Y, Xu H, Gao J K, et al. Recent progress in metal-organic frameworks-based hydrogels and aerogels and their applications[J]. Coordination Chemistry Reviews,2019,398 :213016. doi: 10.1016/j.ccr.2019.213016
[10]	刘志超, 穆洪亮, 李艳, 等. 金属-有机框架材料衍生转换型负极在碱金属离子电池中的应用[J]. 化学进展,2021,33(11):2002-2023 LIU Zhichao, MU Hongliang, LI Yan, et al. Application of metal-organic frameworks-derived conversion-type anodes in alkali metal-ion batteries[J]. Progress in Chemistry,2021,33 (11):2002-2023.
[11]	Li Y Z, Fu Z H, Xu G. Metal-organic framework nanosheets: preparation and applications[J]. Coordination Chemistry Reviews,2019,388 :79-106. doi: 10.1016/j.ccr.2019.02.033
[12]	朱刚, 李辉, 强明礼, 等. 金属-有机骨架在生物质及其衍生化学品中的应用[J]. 林业工程学报,2021,6(6):23-34 ZHU Gang, LI Hui, QIANG Mingli, et al. Application and research progress of metal-organic framework materials in biomass and its derived chemicals[J]. Journal of Forestry Engineering,2021,6 (6):23-34.
[13]	Qiu S L, Xue M, Zhu G S. Metal-organic framework membranes: from synthesis to separation application[J]. Chemical Society Reviews,2014,43 (16):6116-6140. doi: 10.1039/C4CS00159A
[14]	廖学巍, 刘旸, 王琛. 纳米尺度MOFs在肿瘤及肿瘤标志物生物学成像中的研究进展[J]. 分析测试学报,2022,41(4):476-485 doi: 10.19969/j.fxcsxb.21120704 LIAO Xuewei, LIU Yang, WANG Chen. Recent progress in nanoscale MOFs for biological imaging of tumors and tumor markers[J]. Journal of Instrumental Analysis,2022,41 (4):476-485. doi: 10.19969/j.fxcsxb.21120704
[15]	Zhou N, Su F F, Guo C P, et al. Two-dimensional oriented growth of Zn-MOF-on-Zr-MOF architecture: a highly sensitive and selective platform for detecting cancer markers[J]. Biosensors and Bioelectronics,2019,123 :51-58. doi: 10.1016/j.bios.2018.09.079
[16]	Li J, Wang H, Yuan X Z, et al. Metal-organic framework membranes for wastewater treatment and water regeneration[J]. Coordination Chemistry Reviews,2020,404 :213116. doi: 10.1016/j.ccr.2019.213116
[17]	乔俊宇, 李秀涛. 基于MOFs的碳纳米管复合材料的制备和应用进展[J]. 材料工程,2021,49(9):27-40 doi: 10.11868/j.issn.1001-4381.2020.000599 QIAO Junyu, LI Xiutao. Progress in preparation and application of carbon nanotube composites based on MOFs[J]. Journal of Materials Engineering,2021,49 (9):27-40. doi: 10.11868/j.issn.1001-4381.2020.000599
[18]	Rahmanifar M S, Hesari H, Noori A, et al. A dual Ni/Co-MOF-reduced graphene oxide nanocomposite as a high performance supercapacitor electrode material[J]. Electrochimica Acta,2018,275 :76-86. doi: 10.1016/j.electacta.2018.04.130
[19]	赵健全, 吴金金, 卢照, 等. 基于普通模式和电子束减速模式的加速电压对FESEM图像的影响[J]. 分析仪器,2020(2):90-96 doi: 10.3969/j.issn.1001-232x.2020.02.018 ZHAO Jianquan, WU Jinjin, LU Zhao, et al. Impact of different acceleration voltages on FESEM images under normal mode and beam deceleration mode[J]. Analytical Instrumentation,2020 (2):90-96. doi: 10.3969/j.issn.1001-232x.2020.02.018
[20]	Gavrilenko V P, Novikov Y A, Rakov A V, et al. Measurement of the parameters of the electron beam of a scanning electron microscope[C]//NanoScience + Engineering. Proc SPIE 7042, Instrumentation, Metrology, and Standards for Nanomanufacturing II, San Diego, California, USA. 2008, 7042: 107-118.
[21]	曹水良, 梁志红, 尹平河. 不同加速电压对不导电样品扫描电镜图像的影响[J]. 暨南大学学报(自然科学与医学版),2014,35(4):357-360 CAO Shuiliang, LIANG Zhihong, YIN Pinghe. The influence of non-conductive sample SEM images under different acceleration voltage[J]. Journal of Jinan University (Natural Science & Medicine Edition),2014,35 (4):357-360.