Electron holography of thin amorphous carbon films: Measurement of the mean inner potential and a thickness-independent phase shift

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• 作者：Matthias Wanner ; David Bach ; Dagmar Gerthsen ; Ralph Werner and Bernd Tesche
• 刊名：Ultramicroscopy
• 出版年：2006
• 出版时间：March 2006
• 年：2006
• 卷：106
• 期：4-5
• 页码：341-345
• 全文大小：303 K

文摘

The phase shift induced by thin amorphous carbon films with thicknesses between 1 and 16 nm was measured by electron holography in a transmission electron microscope. Large phase shifts Δφ are observed as the thickness of the amorphous C films decreases which cannot be described by the well-known equation Δφ=C_EV₀t (V₀: mean inner Coulomb potential of the material, t: sample thickness). Data plotted in a Δφ vs. t diagram can be well-fitted by a modified equation Δφ=C_EV₀t+φ_add. The mean inner Coulomb potential of the amorphous carbon with a density of 1.75 g/cm³ was determined to be 9.09 V which is consistent with previous experimental data for amorphous carbon with a higher density. The thickness-independent phase offset φ_add of 0.497 rad is large for amorphous carbon under the given experimental conditions. We suggest that a surface-related electrostatic potential is responsible for the thickness-independent contribution φ_add.