Probing the electrostatic potential of charged dislocations inn−GaNandn−ZnOepilayers by transmission electron holography

2006 ◽  
Vol 73 (24) ◽  
Author(s):  
E. Müller ◽  
D. Gerthsen ◽  
P. Brückner ◽  
F. Scholz ◽  
Th. Gruber ◽  
...  
Keyword(s):  
Electrostatic Potential ◽  
Electron Holography ◽  
Transmission Electron

Sample Preparation for Precise and Quantitative Electron Holographic Analysis of Semiconductor Devices

2006 ◽  
Vol 12 (4) ◽  
pp. 295-301 ◽  
Author(s):  
Myung-Geun Han ◽  
Jing Li ◽  
Qianghua Xie ◽  
Peter Fejes ◽  
James Conner ◽  
...  
Keyword(s):  
Electrostatic Potential ◽  
Phase Changes ◽  
Electron Holography ◽  
Gate Length ◽  
Ion Milling ◽  
Minimum Thickness ◽  
Transmission Electron ◽  
Silica Suspension ◽  
Length Separation ◽  
Effect Transistor

Wedge polishing was used to prepare one-dimensional Si n-p junction and Si p-channel metal-oxide-silicon field effect transistor (pMOSFET) samples for precise and quantitative electrostatic potential analysis using off-axis electron holography. To avoid artifacts associated with ion milling, cloth polishing with 0.02-μm colloidal silica suspension was used for final thinning. Uniform thickness and no significant charging were observed by electron holography analysis for samples prepared entirely by this method. The effect of sample thickness was investigated and the minimum thickness for reliable results was found to be ∼160 nm. Below this thickness, measured phase changes were smaller than expected. For the pMOSFET sample, quantitative analysis of two-dimensional electrostatic potential distribution showed that the metallurgical gate length (separation between two extension junctions) was ∼54 nm, whereas the actual gate length was measured to be ∼70 nm by conventional transmission electron microscopy. Thus, source and drain junction encroachment under the gate was 16 nm.

Off-Axis Electron Holography of Unbiased and Reverse-Biased Focused Ion Beam Milled Sip-nJunctions

2005 ◽  
Vol 11 (1) ◽  
pp. 66-78 ◽  
Author(s):  
Alison C. Twitchett ◽  
Rafal E. Dunin-Borkowski ◽  
Robert J. Hallifax ◽  
Ronald F. Broom ◽  
Paul A. Midgley
Keyword(s):  
Electrostatic Potential ◽  
Reverse Bias ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Specimen Preparation ◽  
Electron Holography ◽  
Thin Sample ◽  
Transmission Electron ◽  
Milled Sample

Off-axis electron holography is used to measure electrostatic potential profiles across a siliconp-njunction, which has been prepared for examination in the transmission electron microscope (TEM) in two different specimen geometries using focused ion beam (FIB) milling. Results are obtained both from a conventional unbiased FIB-milled sample and using a novel sample geometry that allows a reverse bias to be applied to an FIB-milled samplein situin the TEM. Computer simulations are fitted to the results to assess the effect of TEM specimen preparation on the charge density and the electrostatic potential in the thin sample.

Electron holography in materials science

1991 ◽  
Vol 49 ◽  
pp. 670-671
Author(s):  
Hannes Lichte ◽  
Edgar Voelkl
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Materials Science ◽  
Fourier Spectrum ◽  
Object Wave ◽  
Electron Holography ◽  
Reconstruction Procedure ◽  
Numerical Reconstruction ◽  
Transmission Electron ◽  
Unique Interpretation

The object wave o(x,y) = a(x,y)exp(iφ(x,y)) at the exit face of the specimen is described by two real functions, i.e. amplitude a(x,y) and phase φ(x,y). In stead of o(x,y), however, in conventional transmission electron microscopy one records only the real intensity I(x,y) of the image wave b(x,y) loosing the image phase. In addition, referred to the object wave, b(x,y) is heavily distorted by the aberrations of the microscope giving rise to loss of resolution. Dealing with strong objects, a unique interpretation of the micrograph in terms of amplitude and phase of the object is not possible. According to Gabor, holography helps in that it records the image wave completely by both amplitude and phase. Subsequently, by means of a numerical reconstruction procedure, b(x,y) is deconvoluted from aberrations to retrieve o(x,y). Likewise, the Fourier spectrum of the object wave is at hand. Without the restrictions sketched above, the investigation of the object can be performed by different reconstruction procedures on one hologram. The holograms were taken by means of a Philips EM420-FEG with an electron biprism at 100 kV.

Reconstruction of electron holograms recorded in a non-FEG, non-biprism TEM

1995 ◽  
Vol 53 ◽  
pp. 618-619
Author(s):  
Z.L. Wang
Keyword(s):  
Electron Microscope ◽  
Single Crystal ◽  
Experimental Technique ◽  
Transmission Electron Microscope ◽  
The Other ◽  
Electron Holography ◽  
Transmission Electron ◽  
Coherent Sources ◽  
Imaging Theory ◽  
Normal Specimen

An experimental technique for performing electron holography using a non-FEG, non-biprism transmission electron microscope (TEM) has been introduced by Ru et al. A double stacked specimens, one being a single crystal foil and the other the specimen, are loaded in the normal specimen position in TEM. The single crystal, which is placed onto the specimen, is responsible to produce two beams that are equivalent to two virtual coherent sources illuminating the specimen beneath, thus, permitting electron holography of the specimen. In this paper, the imaging theory of this technique is described. Procedures are introduced for digitally reconstructing the holograms.

Application of electron holography to material science studies on magnetic domain states of small particles

1993 ◽  
Vol 51 ◽  
pp. 1028-1029
Author(s):  
T. Hirayama ◽  
Q. Ru ◽  
T. Tanji ◽  
A. Tonomura
Keyword(s):  
Magnetic Field ◽  
Material Science ◽  
Science Studies ◽  
Phase Distribution ◽  
Carbon Film ◽  
Objective Lens ◽  
Electron Holography ◽  
Transform Method ◽  
Transmission Electron ◽  
Thin Carbon

The observation of small magnetic materials is one of the most important applications of electron holography to material science, because interferometry by means of electron holography can directly visualize magnetic flux lines in a very small area. To observe magnetic structures by transmission electron microscopy it is important to control the magnetic field applied to the specimen in order to prevent it from changing its magnetic state. The easiest method is tuming off the objective lens current and focusing with the first intermediate lens. The other method is using a low magnetic-field lens, where the specimen is set above the lens gap.Figure 1 shows an interference micrograph of an isolated particle of barium ferrite on a thin carbon film observed from approximately [111]. A hologram of this particle was recorded by the transmission electron microscope, Hitachi HF-2000, equipped with an electron biprism. The phase distribution of the object electron wave was reconstructed digitally by the Fourier transform method and converted to the interference micrograph Fig 1.

On the Faceting of Polar Ceramic Surfaces: Microscopy and Holography Studies of MGO(111) Surfaces

1996 ◽  
Vol 54 ◽  
pp. 366-367
Author(s):  
M. Gajdardziska-Josifovska ◽  
B. G. Frost ◽  
E. Völkl ◽  
L. F. Allard
Keyword(s):  
Electron Microscopy ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Electron Holography ◽  
Flat Surfaces ◽  
Transmission Electron ◽  
Excess Surface ◽  
Polar Surfaces ◽  
Salt Structure ◽  
Crystallographic Planes

Polar surfaces are those crystallographic faces of ionically bonded solids which, when bulk terminated, have excess surface charge and a non-zero dipole moment perpendicular to the surface. In the case of crystals with a rock salt structure, {111} faces are the exemplary polar surfaces. It is commonly believed that such polar surfaces facet into neutral crystallographic planes to minimize their surface energy. This assumption is based on the seminal work of Henrich which has shown faceting of the MgO(111) surface into {100} planes giving rise to three sided pyramids that have been observed by scanning electron microscopy. These surfaces had been prepared by mechanical polishing and phosphoric acid etching, followed by Ar+ sputtering and 1400 K annealing in ultra-high vacuum (UHV). More recent reflection electron microscopy studies of MgO(111) surfaces, annealed in the presence of oxygen at higher temperatures, have revealed relatively flat surfaces stabilized by an oxygen rich reconstruction. In this work we employ a combination of optical microscopy, transmission electron microscopy, and electron holography to further study the issue of surface faceting.

Characterization of JEOL 3000f TEM Equipped for Electron Holography

2000 ◽  
Vol 6 (S2) ◽  
pp. 228-229
Author(s):  
M. A. Schofield ◽  
Y. Zhu
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Design Of Experiment ◽  
Electron Holography ◽  
Fringe Spacing ◽  
Interference Fringes ◽  
Transmission Electron ◽  
Careful Design

Quantitative off-axis electron holography in a transmission electron microscope (TEM) requires careful design of experiment specific to instrumental characteristics. For example, the spatial resolution desired for a particular holography experiment imposes requirements on the spacing of the interference fringes to be recorded. This fringe spacing depends upon the geometric configuration of the TEM/electron biprism system, which is experimentally fixed, but also upon the voltage applied to the biprism wire of the holography unit, which is experimentally adjustable. Hence, knowledge of the holographic interference fringe spacing as a function of applied voltage to the electron biprism is essential to the design of a specific holography experiment. Furthermore, additional instrumental parameters, such as the coherence and virtual size of the electron source, for example, affect the quality of recorded holograms through their effect on the contrast of the holographic fringes.

Mapping the electrostatic potential across AlGaN∕AlN∕GaN heterostructures using electron holography

2007 ◽  
Vol 90 (3) ◽  
pp. 032101 ◽  
Author(s):  
Z. H. Wu ◽  
M. Stevens ◽  
F. A. Ponce ◽  
W. Lee ◽  
J. H. Ryou ◽  
...  
Keyword(s):  
Electrostatic Potential ◽  
Electron Holography

scholarly journals Three-dimensional reconstructions of electrostatic potential distributions with 1.5-nm resolution using off-axis electron holography

Microscopy ◽  
2011 ◽  
Vol 61 (2) ◽  
pp. 77-84 ◽  
Author(s):  
Toshiaki Tanigaki ◽  
Shinji Aizawa ◽  
Takahiro Suzuki ◽  
Akira Tonomura
Keyword(s):  
Electrostatic Potential ◽  
Three Dimensional ◽  
Electron Holography
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