The Art of the Possible: An Overview of Catalyst Specimen Preparation Techniques for TEM Studies

1987 ◽  
Vol 115 ◽  
Author(s):  
Stephen B. Rice ◽  
Michael M. J. Treacy
Keyword(s):  
Model Systems ◽  
Specimen Preparation ◽  
Journal Articles ◽  
Advantages And Disadvantages ◽  
Transmission Electron ◽  
Specific Material ◽  
Traditional Approaches ◽  
Preparation Techniques ◽  
Numerous Journal ◽  
Catalyst Specimen

ABSTRACTObtaining useful microstructural information about catalysts requires appropriate procedures for preparing specimens for the transmission electron microscope. Unfortunately, most descriptions of catalyst specimen preparation are scattered throughout numerous journal articles or are unavailable. Traditional techniques for preparing heterogeneous catalyst powders include primarily dilute dispersion and ultramicrotomy. The advantages and disadvantages of these will be discussed in terms of information obtainable and possible artifacts. In addition, techniques for preparing layered materials, as well as some novel approaches and model systems, will be presented. With these, as with more traditional approaches, the best method for a specific material will be arrived at only through experimentation. Our aim is to describe a variety of possibilities for getting an already synthesized catalyst into the microscope suitably neat, thin, and artifactfree.

Characterization of FIB Damage in Silicon

1999 ◽  
Vol 5 (S2) ◽  
pp. 740-741 ◽  
Author(s):  
C.A. Urbanik ◽  
B.I. Prenitzer ◽  
L.A. Gianhuzzi ◽  
S.R. Brown ◽  
T.L. Shofner ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Target Material ◽  
Beam Current ◽  
Specimen Preparation ◽  
Transfer Energy ◽  
Transmission Electron ◽  
Preparation Techniques ◽  
Reactive Gas

Focused ion beam (FIB) instruments are useful for high spatial resolution milling, deposition, and imaging capabilities. As a result, FIB specimen preparation techniques have been widely accepted within the semiconductor community as a means to rapidly prepare high quality, site-specific specimens for transmission electron microscopy (TEM) [1]. In spite of the excellent results that have been observed for both high resolution (HREM) and standard TEM specimen preparation applications, a degree of structural modification is inherent to FIB milled surfaces [2,3]. The magnitude of the damage region that results from Ga+ ion bombardment is dependent on the operating parameters of the FIB (e.g., beam current, beam voltage, milling time, and the use of reactive gas assisted etching).Lattice defects occur as a consequence of FIB milling because the incident ions transfer energy to the atoms of the target material. Momentum transferred from the incident ions to the target atoms can result in the creation of point defects (e.g., vacancies, self interstitials, and interstitial and substitutional ion implantation), the generation of phonons, and plasmon excitation in the case of metal targets.

High-resolution microscopy of ceramic surfaces

1993 ◽  
Vol 51 ◽  
pp. 962-963
Author(s):  
J. Bentley
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Film Growth ◽  
Specimen Preparation ◽  
Force Microscopy ◽  
Advantages And Disadvantages ◽  
Transmission Electron ◽  
Ceramic Surfaces ◽  
Wide Range ◽  
Scanning Transmission

The characterization of ceramic surfaces plays an important role in understanding a wide variety of properties such as fracture, wear, crack initiation, oxidation, sintering, and thin film growth on substrates. Three major microscopies are employed to obtain nanometer-scale resolution of ceramic surfaces: scanning electron microscopy (SEM), (scanning) transmission electron microscopy (STEM or TEM) especially in the glancing-incidence reflection modes, and scanning tip microscopies - most notably atomic force microscopy (AFM). Each technique has its own set of characteristics, advantages, and disadvantages and is usually complementary to the others.Conventional SEM is quick and easy to implement. As a mature technique, the contrast mechanisms, although sometimes complex, are largely well understood; computer programs for image simulation are available. The technique is applicable to a wide range of materials and specimen sizes; usually, little specimen preparation is involved. Charging of electrically insulating ceramics has traditionally been overcome by coating but, at high resolution, the faithful representation of the structure then becomes of some concern.

Microstructural Characterization of Automated Specimen Preparation for TEM Analysis

2000 ◽  
Vol 6 (S2) ◽  
pp. 528-529
Author(s):  
C. Urbanik Shannon ◽  
L. A. Giannuzzi ◽  
E. M. Raz
Keyword(s):  
Focused Ion Beam ◽  
Preparation Method ◽  
Ion Beam ◽  
Microstructural Characterization ◽  
Specimen Preparation ◽  
Tem Analysis ◽  
Area Of Interest ◽  
Transmission Electron ◽  
Preparation Techniques

Automated specimen preparation for transmission electron microscopy has the obvious advantage of saving personnel time. While some people may perform labor intensive specimen preparation techniques quickly, automated specimen preparation performed in a timely and reproducible fashion can significantly improve the throughput of specimens in an industrial laboratory. The advent of focused ion beam workstations for the preparation of electron transparent membranes has revolutionized TEM specimen preparation. The FIB lift-out technique is a powerful specimen preparation method. However, there are instances where the “traditional” FIB method of specimen preparation may be more suitable. The traditional FIB method requires that specimens must be prepared so that the area of interest is as thin as possible (preferably less than 50 μm) prior to FIB milling. Automating the initial specimen preparation for brittle materials (e.g., Si wafers) may be performed using the combination of cleaving and sawing techniques as described below.

scholarly journals A Versatile and Affordable Plunge Freezing Instrument for Preparing Frozen Hydrated Specimens for Cryo Transmission Electron Microscopy (CryoEM)

2009 ◽  
Vol 17 (2) ◽  
pp. 14-17 ◽  
Author(s):  
Linda Melanson
Keyword(s):  
Electron Microscopy ◽  
High Vacuum ◽  
Specimen Preparation ◽  
Macromolecular Assemblies ◽  
Preservation Method ◽  
Transmission Electron ◽  
Structural Details ◽  
Soft Polymer ◽  
2D Crystals ◽  
Preparation Techniques

CryoEM is a powerful tool in the arsenal of structural biologists and soft polymer chemists. Hydrated specimens require a preservation method that will counteract the effects of the electron beam and the high vacuum environment of the electron microscope. Classical specimen preparation techniques using chemical fixatives are not able to capture the native structure of the once hydrated specimen perfectly. In contrast to classical methods for preserving specimens for electron microscopy, rapid freezing of radiation-sensitive specimens such as dispersed biological macromolecular assemblies, 2D crystals, and colloids allows the structural details of the specimen to be captured in their essentially native state to near atomic resolution.

Improving Signal-to-Noise Limits in High Resolution Transmission Electron Microscopy

1986 ◽  
Vol 82 ◽  
Author(s):  
J.M. Gibson ◽  
M.L. McDonald
Keyword(s):  
Surface Cleaning ◽  
Specimen Preparation ◽  
Ion Milling ◽  
Noise Levels ◽  
Signal To Noise ◽  
Transmission Electron ◽  
Lattice Images ◽  
Preparation Techniques ◽  
Image Quantitation

ABSTRACTSignal-to-noise ratios for Si <110> lattice images are measured for a variety of different specimen preparation techniques, including ion-milling, chemical polishing, cleavage and in-situ surface cleaning by heating. The noise levels are significantly lower in the latter, possibly permitting new classes of experiments in image quantitation and impurity imaging.

Preparation of fragile catalyst materials for TEM

1995 ◽  
Vol 53 ◽  
pp. 412-413
Author(s):  
K.L. More ◽  
D.W. Coffey ◽  
T.S. Geer
Keyword(s):  
Spatial Information ◽  
Substrate Surface ◽  
Model Systems ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Cross Sectional ◽  
Process Modification ◽  
Transmission Electron ◽  
Section Technique ◽  
Catalyst Systems

A novel specimen preparation technique for transmission electron microscopy (TEM) has been developed which allows for the preservation of constituent placement within a variety of diesel and automotive catalyst materials. The standard preparation method for imaging catalyst particles and washcoat constituents has been to use powders scraped from the substrate surface. However, while limited imaging of fine scale structures is possible on clean specimens using this method, all cross-sectional spatial information is lost. Thus, scraped powder specimens cannot be used to directly image surface effects in the TEM or to view large areas of "intact" material in these catalyst systems. Also, for many microscopy investigations such as electron energy loss spectroscopy and high resolution imaging, powders can be too thick. Other preparation techniques have also been used, for example ultramicrotomy and model systems, with some limited success. It is clear that by preparing TEM specimens using this cross-section technique, changes in microstructure to either precious metal particles or washcoat constituents with distance from the exposed surface can be evaluated as a function of aging, engine use, or process modification.

The role of specimen morphology in the preparation of High-TC superconductors for Transmission Electron Microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 66-67
Author(s):  
M. Powers
Keyword(s):  
Low Cost ◽  
Oxide Superconductors ◽  
Specimen Preparation ◽  
Layered Crystal ◽  
Preparation Technique ◽  
Ion Milling ◽  
Tem Analysis ◽  
Transmission Electron ◽  
Preparation Techniques

It is vital in TEM investigations, especially for high resolution studies, that specimen quality be optimized and the information desired in a particular TEM analysis often prescribes the method of specimen preparation required. We have found that the morphology of a bulk superconductor sample can significantly influence the ultimate success of the preparation technique utilized.Methods employed for the production of electron transparent foils of ceramic oxide superconductors include mechanical grinding, cleavage, jet polishing, ultramicrotomy and ion milling. Grinding and cleavage are both low cost, quick and easy specimen preparation techniques. However, because of the layered crystal structures of these materials, they display a marked tendency to cleave along (001) planes, and hence the range of crystallographic orientations available with these methods is restricted. With grinding in particular, mechanical deformation can be a problem while with cleavage, transparent areas are confined to the vicinity of particle edges.

The application of Transmission Electron Microscope to semiconductor device problems

1993 ◽  
Vol 51 ◽  
pp. 796-797
Author(s):  
Brian Cunningham ◽  
J. Daniel Mis
Keyword(s):  
Semiconductor Device ◽  
Bipolar Transistors ◽  
Current Gain ◽  
Specimen Preparation ◽  
Device Performance ◽  
Structural Components ◽  
Interfacial Layers ◽  
Transmission Electron ◽  
Preparation Techniques ◽  
Crystal Interface

In the last 5-10 years there has been a large increase in the application of TEM to semiconductor device problems. This increase is due to several factors. Higher density chips and decreasing device dimensions have led to structural components which are frequently in the nanometer range. The ease with which present day microscopes can measure nanometer dimensions along with the advances in specimen preparation techniques now make the TEM invaluable as a tool for routine constructional analysis. As device dimensions shrink, the structure and composition of thin interfacial layers becomes increasingly important to device performance. In fact, in some cases, such as the emitter polysilicon to single crystal interface in bipolar transistors, the interface can dominate device parametrics such as current gain and emitter resistance. The ability to examine these interfaces in actual devices is therefore extremely important, and TEM is again proving to be uniquely suited to this task.

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