Thickness determination by measuring electron transmission in the TEM at 200kV

Pozsgai, I.

doi:10.1016/s0304-3991(97)00024-7

Cited by 16 publications

(9 citation statements)

References 4 publications

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“…4 For samples thin compared to a scattering mean free path, Beer's law is valid. Beer's law has been shown to hold empirically for films of Ti, Ge, Ag, and Au up to 100 or 200 nm thick, 5 which covers the typical thicknesses used in transmission electron microscopy. For thicker samples, the rule of exponential attenuation is no longer valid for transmission electron microscopy.…”

Section: A Introductionmentioning

confidence: 98%

Theory of bright-field scanning transmission electron microscopy for tomography

Levine

2005

Journal of Applied Physics

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Radiation transport theory is applied to electron microscopy of samples composed of one or more materials. The theory, originally due to Goudsmit and Saunderson, assumes only elastic scattering and an amorphous medium dominated by atomic interactions. For samples composed of a single material, the theory yields reasonable parameter-free agreement with experimental data taken from the literature for the multiple scattering of 300-keV electrons through aluminum foils up to 25μm thick. For thin films, the theory gives a validity condition for Beer’s law. For thick films, a variant of Molière’s theory [V. G. Molière, Z. Naturforschg. 3a, 78 (1948)] of multiple scattering leads to a form for the bright-field signal for foils in the multiple-scattering regime. The signal varies as [tln(e1−2γt∕τ)]−1 where t is the path length of the beam, τ is the mean free path for elastic scattering, and γ is Euler’s constant. The Goudsmit–Saunderson solution interpolates numerically between these two limits. For samples with multiple materials, elemental sensitivity is developed through the angular dependence of the scattering. From the elastic scattering cross sections of the first 92 elements, a singular-value decomposition of a vector space spanned by the elastic scattering cross sections minus a delta function shows that there is a dominant common mode, with composition-dependent corrections of about 2%. A mathematically correct reconstruction procedure beyond 2% accuracy requires the acquisition of the bright-field signal as a function of the scattering angle. Tomographic reconstructions are carried out for three singular vectors of a sample problem with four elements Cr, Cu, Zr, and Te. The three reconstructions are presented jointly as a color image; all four elements are clearly identifiable throughout the image.

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Section: A Introductionmentioning

confidence: 98%

Theory of bright-field scanning transmission electron microscopy for tomography

Levine

2005

Journal of Applied Physics

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“…8 Herein, the morphology refers to the projected two-dimensional (2D) shape of NPs seen in TEM micrographs. PEBBLES is intended for the frequent and tedious chore of measuring the morphology of a NP population and not for thickness measurement [9][10][11] nor reconstruction of the 3D shape. 12 After taking some medium-resolution TEM micrographs with the appropriate instrumental settings, one has to measure the morphology of many hundred NPs in order to achieve a significant description of the morphological characteristics of the NP population.…”

Section: Introductionmentioning

confidence: 99%

Pebbles and PebbleJuggler: software for accurate, unbiased, and fast measurement and analysis of nanoparticle morphology from transmission electron microscopy (TEM) micrographs

et al. 2012

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Pebbles is a user-friendly software program which implements an accurate, unbiased, and fast method to measure the morphology of a population of nanoparticles (NPs) from TEM micrographs. The morphological parameters of the projected NP shape are obtained by fitting intensity models to the TEM micrograph. Pebbles can be used either in automatic mode, where both fitting and validation are reliably carried out with minimal human intervention, and in manual mode, where the user has full control on the fitting and validation steps. Accuracy in diameter measurement has been shown to be ≲1%. When operated in automatic mode, Pebbles can be very fast. The effective speed of 1 NP s⁻¹ has been achieved in favorable cases (packed monolayer of NPs). Since Pebbles is based on a local modeling procedure, it successfully treats cases such as low contrast NPs, NPs with significant diffraction scattering, and inhomogeneous background which often make conventional thresholding procedures fail. Pebbles is accompanied by PebbleJuggler, a software program for the statistical analysis of the sets of best-fit NP models created by Pebbles. Effort has been devoted to make Pebbles and PebbleJuggler the most user-friendly and the least user-tedious we could. Pebbles and PebbleJuggler are available at http://pebbles.istm.cnr.it.

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“…The determination of the thickness of a transmission electron microscope (TEM) specimen is an essential prerequisite for quantitative microscopy. A large number of methods have been devised for achieving this over the years (von Heimendahl, 1964; Hall & Vander Sande, 1975; Kelly et al ., 1975; Morris et al ., 1980; Allen, 1981; Berriman et al ., 1984; Egerton & Cheng, 1987; Scott & Love, 1987; Horita et al ., 1989; Egerton, 1996; Pozgai, 1997). Many of these methods have severe limitations, both in terms of the types of materials to which they can be applied and in their accuracy.…”

Section: Introductionmentioning

confidence: 99%

Determination of mean free path for energy loss and surface oxide film thickness using convergent beam electron diffraction and thickness mapping: a case study using Si and P91 steel

Mitchell

2006

Journal of Microscopy

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SummaryDetermining transmission electron microscope specimen thickness is an essential prerequisite for carrying out quantitative microscopy. The convergent beam electron diffraction method is highly accurate but provides information only on the small region being probed and is only applicable to crystalline phases. Thickness mapping with an energy filter is rapid, maps an entire field of view and can be applied to both crystalline and amorphous phases. However, the thickness map is defined in terms of the mean free path for energy loss ( λ ), which must be known in order to determine the thickness. Convergent beam electron diffraction and thickness mapping methods were used to determine λ for two materials, Si and P91 steel. These represent best-and worst-case scenario materials, respectively, for this type of investigation, owing to their radically different microstructures. The effects of collection angle and the importance of dynamical diffraction contrast are also examined. By minimizing diffraction contrast effects in thickness maps, reasonably accurate ( ± 15%) values of λ were obtained for P91 and accuracies of ± 5% were obtained for Si. The correlation between the convergent beam electron diffraction-derived thickness and the log intensity ratios from thickness maps also permits estimation of the thickness of amorphous layers on the upper and lower surfaces of transmission electron microscope specimens. These estimates were evaluated for both Si and P91 using cross-sectional transmission electron microscopy and were found to be quite accurate.

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Thickness determination by measuring electron transmission in the TEM at 200kV

Cited by 16 publications

References 4 publications

Theory of bright-field scanning transmission electron microscopy for tomography

Theory of bright-field scanning transmission electron microscopy for tomography

Pebbles and PebbleJuggler: software for accurate, unbiased, and fast measurement and analysis of nanoparticle morphology from transmission electron microscopy (TEM) micrographs

Determination of mean free path for energy loss and surface oxide film thickness using convergent beam electron diffraction and thickness mapping: a case study using Si and P91 steel

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