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Wolfgang Grünewald, PhD

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  • Has a PhD in experimental physics, Department of Physics, Technical University of Chemnitz, Germany
  • In his diploma and dissertation, he dealt with TEM investigation of thin films and ion milling as appropriate sample preparation method
  • Worked 12 years as application manager at Bal-Tec, in development of ion milling systems and preparation methods
  • Since 2008, worldwide specialist for Solid States sample preparation within Leica Microsystems
  • Owner of 5 patents and author of many scientific publications
  • Free Webinar-on-Demand: Mechanical pre-preparation and ion milling for SEM observation

    See how the unique combination of pre-preparation system and ion milling system makes fast site specific sample preparation for Scanning Electron Microscopy or optical microscopy possible.
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  • Contrast Enhancement of Polycrystalline Metals - Sample Preparation for SEM

    Application Note - Ion milling is a perfect alternative for chemical etching, especially for polycrystalline metals, such as copper. Ion milling can be used to increase the contrast of the grain structure and their interfaces. In contrast to chemical etching the milling process is clean, safe and easy to operate. Ion energy and milling time depend on the milling rate of the metal.
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  • Cross Sectioning of Cadmiumsulphide (CdS) for Cathodoluminescence

    Cathodoluminescence can be used to achieve spectra and high resolution images of impurity and structural defects in semicondoctors, minerals and insulating materials. This application note explains how to prepare a perfect sample surface for carhodoluminescence and how to use ion beam slope cutting to prepare the sample surface free of any preparation artefacts.
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  • Cross Sectioning of Copper for Electron Backscattered Diffraction (EBSD)

    Application Note for Leica EM TIC 3X - Electron Backscattered Diffraction (EBSD) is a surface technique creating diffraction patterns (Kikuchi-bands). It can be used for crystal orientation mapping, defect studies, phase identification, grain boundary studies and morphological studies. The information depth is just a few nm, therefore good sample preparation is very important to avoid damages.
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  • Porous Ceramics - Sample Preparation for SEM

    Application Note for Leica EM RES102 - Ceramic membrane filters with pore sizes down to a few nanometres must be investigated in cross-section with regard to the structure of the pores. The smallest pores are of special interest. In most cases, conventional grinding methods cannot be used for such problems, as the pore structure would be distorted. This applies in particular to the pores in the nanometre range.
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  • Removal of Surface Layers - Sample Preparation for SEM and TEM

    Application Note for Leica EM RES102 - Sometimes it is necessary to remove surface layers to gain access to the real surface structure. That can be a native oxide, or layers coming from the preparation process itself, like re-deposition. Depending on the layers thickness and the energy used for the cleaning process, it takes between a few seconds and half an hour. The energy depends on the milling rate of the material.
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  • Semiconductor Structures with Large Differences in Hardness - Sample Preparation for SEM

    Application Note for Leica EM RES102 - In most cases, multi-layer structures or material combinations with large differences in hardness cannot be processed with conventional polishing techniques, or can only be very poorly processed. Due to the large differences in hardness, blurring or edge-rounding occurs, which distorts the original structure. In the application example shown, we are dealing with a solder ball structure. The goal was to determine the solder structure. The use of conventional grinding and polishing techniques was not possible due to the large differences in hardness between the solder ball and other materials in the sample.
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  • Cross Section of Solar Cells

    Application Note for Leica EM TIC020, Leica EM TIC 3X - Cross section of a complete solar cell.
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  • Cross Sectioning of a Multilayer System - Preparation of a Perfect Sample Surface for EBSD

    Application Note for Leica EM TIC 3X - Electron Backscattered Diffraction (EBSD) is a surface technique creating a diffraction pattern (Kikuchi-bands). It can be used for crystal orientation mapping, defect studies, phase identification, grain boundary studies and morphology studies. The information depth is just a few nm. Therefore good sample preparation is very important to avoid any damage. This is very difficult in case of multilayer system with big differences in hardness.
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  • Multilayer Systems with Widely Different Sputter Rates - Sample Preparation for TEM

    Application Note for Leica EM RES102 - The multi-layer system to be prepared in cross-section consists of a Si substrate, a TiN layer with a thickness of a few nm and a 500 nm W layer. All these components have extreme differences in their hardness, their atomic weight and in their sputter rates. A preparation of this kind of samples with sample rotation would lead to a wall overlying the area of the layers.
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  • In-Containing Compound Semiconductors - Sample Preparation for TEM

    Application Note for Leica EM RES102 - Previous studies showed that surface accumulation of In occurs when InP was milled in a conventional way with Ar ions. The consequence is In islands on the sample surface. This leads to low quality of TEM samples. To remove these islands, reactive ion milling with iodine ions (RIBE / CAIBE) can be used. This method has the disadvantage of polluting the ion guns and the vacuum system of the ion milling device and leads to chemical reactions with the sample material. To avoid these problems we prepared these samples very gently with low energy Ar ions.
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  • "Shallow Trench Isolation" Structures - Sample Preparation for TEM

    Application Note for Leica EM RES102 - The cross-sectional preparation of structured semiconductor materials requires a very thorough mechanical pre-preparation. In doing this, it must be ensured that the structure of interest should be located as close to the centre of the sample as possible. As the sample will be ion milled from both sides, a specific preparation of the structure is necessary in most cases, which means that you must thin these structures from both sides.
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  • Paper Samples - Sample Preparation for SEM

    Application Note for Leica EM RES102 - A coated paper sample has been prepared with ion beam slope cutting in order to test the procedure with regard to its applicability. With the use of ion beam slope cutting a cross section of paper could be prepared. On the basis of this sample processing, it was possible to show the largely unaffected original structure of the thermally-sensitive paper in the scanning electron microscope.
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  • Metal Films and Sheets - Sample Preparation for TEM

    Application Note for Leica EM RES102 - Most metal films already have a thickness that requires no further mechanical pre-preparation. Frequently, however, they are also domed, which can lead to undefined milling angles. This is a disadvantage, particularly for films that contain inclusions, and that therefore mostly require very flat milling angles. Metal sheets are thicker than 100 µm. Mechanical pre-preparation is necessary to obtain an acceptable initial thickness and a good surface quality for ion milling.
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  • Cross-Sectional Preparation of Structured Semiconductor Materials for TEM

    Application Note for Leica EM RES102 - The vertical layer construction of a semiconductor structure should be examined as a TEM cross-sectional sample. In addition to the specific preparation of the desired structure, the widely different sputter rates and atomic weights of the individual components represent the level of difficulty involved with this preparation problem.
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  • Contrast Enhancement of Polished Cross Sections of Semiconductor Structures - Sample Preparation for SEM

    Application Note for Leica EM RES102 - The surfaces of polished cross sections often show fine scratches and residues of the removed material or of the abrasive material. The artefacts are strongly material-dependent, and are mostly only detectable at higher resolutions in the scanning electron microscope. A further problem arises from the fact that the ground section mostly only has low contrast, i.e., in the structures of the semiconductor materials are very difficult to discern. With the use of ion beam milling, the ground sections of semiconductor structures can be "contrasted".
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  • Surface Modification of ZnAg Sample - Sample Preparation for SEM

    Application Note for Leica EM RES102 - By means of cleaning, polishing and contrast enhancement a soft ZnAg sample should be prepared to obtain information concerning the grain structure and interfaces of the sample. The sample is contaminated after mechanical polishing. There are still some scratches on the surface. Grain structure is almost invisible.
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  • Cross Sectioning of Ni/Cu on Steel for EBSD

    Application Note for Leica EM TIC 3X - Electron Backscattered Diffraction (EBSD) is a surface technique creating a diffraction pattern (Kikuchi-bands). It can be used for crystal orientation mapping, defect studies, phase identification, grain boundary studies and morphology studies. The information depth is just a few nm. Therefore a good sample preparation is very important.
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  • Cross Sectioning of Painted Concrete

    Application Note for Leica EM TIC 3X - Ion beam slope cutting is a method that can achieve flat cuts of material combinations consisting of hard and soft materials. Here, cross sectioning of painted concrete is describes in order to visualize the interface between paint and concrete.
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  • Thin Metal Foils with Coatings - Sample Preparation for SEM

    Application Note for Leica EM RES102 - Thin foils are mostly unstable because of their thickness of a few microns. This makes it difficult to do slope cutting without any protection of the sample. A common realisation to protect the sample surface is by sticking a cover glass on top of the sample. Another issue is cutting the foils before ion milling. The sample edge should be flat and sharp without any broken areas. A razor blade is mostly the best solution. A protected sample can salso be sawed with a wire saw.
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  • Cross Sectioning of a Superconductive Wire

    Application Note for Leica EM TIC 3X - Purpose: The shape of the wire is difficult for ion beam slope cutting. Goal: Cross sectional preparation to see the structure of the wire.
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  • Ion Beam Polishing of Sample Surfaces - Sample Preparation for SEM

    Application Note for Leica EM RES102 - Ion milling can be used to reduce the roughness of sample surfaces. Small angles less than 6° with respect to the sample surface are necessary. The high voltage depends on the material to be prepared. The reason for the levelling effect is the different milling angle of flat and rough surface areas. The milling rate is lower for small angles. The rough surface area will be faster milled. Ion polishing is often the final step of sample preparation. The prerequisite is a perfect mechanical prepreparation as samples with deep surface scratches cannot be ion polished. Soft materials usually have a smeared sample surface after mechanical polishing. It is necessary to remove this smeared material before ion polishing. Otherwise the above mentioned polishing effect does not work.
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  • Cleaning of Smeared Sample Surfaces - Sample Preparation for SEM

    Application Note for Leica EM RES102 - Mechanical polishing of soft materials or hard / soft material combinations is tricky. The mechanical polishing process leads very often to smearing of the soft material. The smeared material covers the surface and fills small pores or holes. Grain structures, interfaces and other structural details can be masked. An additional ion milling step with milling angles between 10° C and 15° C with respect to the sample surface can remove or reduce the contamination.
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  • Ceramics - Sample Preparation for TEM

    Application Note for Leica EM RES102 - Ceramic samples are mostly very brittle, and are therefore very difficult to thin mechanically to a low starting thickness for ion beam milling. The ion beam milling of insulators often leads to static charging of the surface of the sample. This, in turn, reduces the sputter rate. When using the Ti standard holder (standard TEM holder), however, sufficient secondary electrons are created by the ion beam also falling on the sample holder to largely compensate for the static charging.
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  • Cross Sectioning of Alumina

    Application Note for Leica EM TIC 3X - Alumina is very difficult to handle and almost impossible to prepare with conventional methods. Ion beam slope cutting is a method that can achieve cross sections of material combinations consisting of hard and soft components.
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