000877846 001__ 877846
000877846 005__ 20240610121213.0
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000877846 0247_ $$2ISSN$$a1866-1807
000877846 020__ $$a978-3-95806-476-8
000877846 037__ $$aFZJ-2020-02470
000877846 041__ $$aEnglish
000877846 1001_ $$0P:(DE-Juel1)165965$$aZheng, Fengshan$$b0$$eCorresponding author$$gmale$$ufzj
000877846 245__ $$aHigh spatial resolution and three-dimensional measurement of charge density and electric field in nanoscale materials using off-axis  electron holography$$f- 2020-07-23
000877846 260__ $$aJülich$$bForschungszentrum Jülich GmbH Zentralbibliothek, Verlag$$c2020
000877846 300__ $$aXIX, 182 S.
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000877846 3367_ $$0PUB:(DE-HGF)11$$2PUB:(DE-HGF)$$aDissertation / PhD Thesis$$bphd$$mphd$$s1595485554_4601
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000877846 4900_ $$aSchriften des Forschungszentrums Jülich. Reihe Schlüsseltechnologien / Key Technologies$$v221
000877846 502__ $$aRWTH Aachen, Diss., 2020$$bDr.$$cRWTH Aachen$$d2020
000877846 520__ $$aThe ability to make local measurements of charge density in nanoscale materials and devices is essential for understanding many material properties. The charge density can then be used to infer the electric field or electrostatic potential within and around the specimen. This information is important for scientists working on subjects such as field electron emissionand atom probe tomography. Off-axis electron holography is a powerful technique that can be used to record the phase shift of a high-energy electron wave travelling through an electron-transparent specimenin a transmission electron microscope. Information about the charge density within the specimen can be retrieved from the measured phase with high spatial resolution. In this thesis, charge density and electric field measurements are performed, both in projection and in three dimensions, with a primary focus on samples that have a needle-shaped geometry. Three approaches are used: an analytical model-dependent approach, a model-independentapproach and an approach based on numerical model-based iterative reconstruction. The model-based iterative approach allows $\textit{a priori}$ information, such as the shape of the object and the influence of charges that are located outside the field of view, to be taken into account. More importantly, it also allows for the reconstruction of three-dimensional charge density distributions from incomplete tomographic tilt of phase images without the artefacts that would be present if conventional tomographic reconstruction algorithms were used. In this thesis, a W$_{5}$O$_{14}$ nanowire is investigated experimentally in the presence of anapplied electrical bias and the charge distribution along it is evaluated. A carbon fibre needle-shaped specimen is then studied, in order to demonstrate the capability of the modelbased iterative approach to measure the three-dimensional charge density, electric field and electrostatic potential both inside and around it. Finally, a systematic investigation of electron-beam-induced charging in a needle-shaped specimen with an insulating Al$_{2}$O$_{3}$ apex is presented, including the dependence of the results on electron dose rate, total dose, temperature, primary electron energy and the surface state of the sample. Great care is required with the acquisition and interpretation of the results, in particular because charging phenomena are sensitive to the electrical conductivity of the sample, the presence of contact potentials and the presence of (unknown) surface states.
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000877846 9201_ $$0I:(DE-Juel1)ER-C-1-20170209$$kER-C-1$$lPhysik Nanoskaliger Systeme$$x0
000877846 9201_ $$0I:(DE-Juel1)PGI-5-20110106$$kPGI-5$$lMikrostrukturforschung$$x1
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