Papers by Keyword: Electron Holography

Abstract: A new method is proposed for mapping of phase distribution in electron holography. A stage-scanning system was used for moving the specimen to obtain a series of holograms with different specimen positions in a fixed electron-optics configuration. By applying a digital aperture which selects an area on holograms with different specimen positions, an interferogram of the specimen can be obtained directly without a complex reconstruction method such as the one using Fourier transformation. Experimental results for a Co particle demonstrated the practicability of this method.

Abstract: The Phenomenon of Laser-Induced Discharging in an Organic Photoconductor Sample Was Directly Observed Using Electron Holography and Sophisticated Techniques for In Situ Observations. Mechanical Friction Was Used to Induce Negative Tribocharges on the Surface of the Photoconductor Sample. the Observation of Equipotential Contour Lines (i.e., the Electric Potential Distribution) outside the Specimen Revealed that the Amount of Tribocharges Was Reduced by the Laser Exposure. Computer Simulations of the Equipotential Lines Provided Useful Information for Evaluating the Quantity of Tribocharges.

Abstract: We performed magnetic imaging of Ni-based ferromagnetic shape memory alloys. The magnetic microstructure was revealed by Lorentz microscopy and electron holography, which are powerful tools based on transmission electron microscopy. Observations of Ni51Fe22Ga27 and Ni50Mn25Al12.5Ga12.5 alloys, both of which have an L21-ordered structure in the parent phase, demonstrated that the antiphase boundaries (i.e., a type of planer defects) caused significant changes in the magnetization distribution due to depression of the atomic order—actually, the magnetization in these alloys depends upon the degree of chemical order. We propose a method which estimates the important magnetic parameters (the magnetocrystalline anisotropy constant and exchange stiffness constant) based on transmission electron microscopy observations. This method should be useful in magnetic measurements of nanometer-scale areas, for which conventional techniques cannot be applied.

Abstract: Electron beam induced deposition (EBID) was carried out with gas introduction systems attached to field emission scanning electron microscope (FE-SEM). Using iron carbonyl and ferrocene, three dimensional (3-D) antenna structures were fabricated in the range of 30-50 nm in diameter and 500-1000 nm in size. Post-deposition annealing of iron nanostructures resulted in the formation of crystalline alpha-iron and iron carbide phases. The iron concentration was controlled by the partial pressure of iron carbonyl and ferrocene. Electron holography observation with field emission transmission electron microscopy (FE-TEM) revealed that the remanent magnetic flux density Br of the nanostructures also depends on the iron concentration.

Abstract: We report on electron holography as a promising candidate for diagnostics in silicon technology and research. Electron holography determines the local phase shift of the electron wave passing through a sample. The phase is proportional to the 2D projected electrostatic potential in the sample and thus reveals p-n junctions and, indirectly, doping. We demonstrate detection of submonolayer boron layers in Si and SiGe, measurement of Ge concentration in SiGe and qualitative 2D oxygen mapping in SiO2/Si structures with 0.5 nm resolution, and comparison of doping in two bipolar transistors with different base implant. Resolution and noise limits are discussed.

Abstract: This paper aims at applying advanced transmission electron microscopy (TEM) to functional materials, such as ultra-soft magnetic films for high-frequency inductors, to reveal the structure-property relationship. The ultimate goal is to delineate a more quantitative way to obtain information of the magnetic induction and local magnetization. Nano-crystalline Fe-Zr-N films have been prepared by DC magnetron reactive sputtering with a thickness between 50 and 500 nm. Conventional TEM and selected area diffraction (SAD), reveal crystallites of sizes ranging between 2 and 30 nm. The films showed a granular or hillock type of roughness with an rms amplitude of 5 nm. In particular this paper concentrates on an analysis of phase maps in electron holography and intensity maps in Lorentz transmission electron microscopy including the thickness variation over the sample. For a particular statistical description of the roughness and values for the roughness it is shown that analytical expressions can be obtained. We demonstrate that starting from the concept of the vector potential in classical electrodynamics these results can be achieved assuming independent stationary Gaussian distributions for the height correlation functions.

Abstract: Magnetic ripple structure of Fe84Nb7B9 is studied by electron holography. The correlation exchange length, effective exchange and anisotropy constants are estimated from a field dependence of ripple wavelength. The function of ripple theory is adjusted with a decay constant, which reflects influence of stray field on the ripple structure. A magnetic hardness at elevated temperature is also observed and analyzed.