In situ TEM sample preparation for surface-sensitive plane view imaging

1991 ◽  
Vol 49 ◽  
pp. 642-643
Author(s):  
R. Ai ◽  
D.N. Dunn ◽  
T.S. Savage ◽  
J.P. Zhang ◽  
L.D. Marks
Keyword(s):  
Sample Preparation ◽  
Surface Science ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
In Situ Tem ◽  
Preparation Technique ◽  
Surface Imaging ◽  
Resolution Electron ◽  
Electron Microscopes ◽  
Plane View

The recent development of ultra high vacuum high resolution electron microscopes has made it possible to use an electron microscope to study surface structures with atomic resolution. Although surface images of Au(110) 2x11 and Si(111) 7x72 reconstructions have been obtained, no standard TEM sample preparation technique for surface imaging has been developed for routine uses. In conventional surface science, the common method of producing an UHV clean sample is a combination of ion sputtering and annealing; can this process be used to produce TEM samples for surface imaging. Our studies show that clean, well order TEM samples can be achieved by this approach.

A Microscope-Compatible Auger Electron Spectrometer

1991 ◽  
Vol 49 ◽  
pp. 992-993
Author(s):  
R. Ai
Keyword(s):  
High Vacuum ◽  
Surface Profile ◽  
Ultra High Vacuum ◽  
Real Surface ◽  
Resolution Electron ◽  
Reflection Electron Microscopy ◽  
Electron Microscopes ◽  
Plane View ◽  
Surface Chemical Analysis

With the recent development of ultra-high vacuum high resolution electron microscopes (UHV-HREM), electron microscopes have become valuable tools for surface studies. Techniques such as surface profile image, surface sensitive plane view, and reflection electron microscopy have been developed to take full advantage of the atomic resolution of HREM to study surface structures. However a complete surface study requires information on both the surface structure and surface chemistry. Therefore in order to turn an electron microscope into a real surface analytical tool, the challenge is to develop a microscopecompatible, surface sensitive tool for in-situ surface chemical analysis.

TEM sample preparation of wear-tested room-temperature pulsed-laser-deposited thin films of MoS2 by ultramicrotomy

1993 ◽  
Vol 51 ◽  
pp. 1118-1119
Author(s):  
Pamela F. Lloyd ◽  
Scott D. Walck
Keyword(s):  
Thin Films ◽  
Sample Preparation ◽  
Room Temperature ◽  
High Vacuum ◽  
Pulsed Laser ◽  
Ultra High Vacuum ◽  
Wear Testing ◽  
Preparation Technique ◽  
Cross Sectional ◽  
Aerospace Applications

Pulsed laser deposition (PLD) is a novel technique for the deposition of tribological thin films. MoS2 is the archetypical solid lubricant material for aerospace applications. It provides a low coefficient of friction from cryogenic temperatures to about 350°C and can be used in ultra high vacuum environments. The TEM is ideally suited for studying the microstructural and tribo-chemical changes that occur during wear. The normal cross sectional TEM sample preparation method does not work well because the material’s lubricity causes the sandwich to separate. Walck et al. deposited MoS2 through a mesh mask which gave suitable results for as-deposited films, but the discontinuous nature of the film is unsuitable for wear-testing. To investigate wear-tested, room temperature (RT) PLD MoS2 films, the sample preparation technique of Heuer and Howitt was adapted.Two 300 run thick films were deposited on single crystal NaCl substrates. One was wear-tested on a ball-on-disk tribometer using a 30 gm load at 150 rpm for one minute, and subsequently coated with a heavy layer of evaporated gold.

Electron spectroscopy in SEM and STEM

1990 ◽  
Vol 48 (2) ◽  
pp. 378-379
Author(s):  
J. A. Venables ◽  
G. G. Hembree ◽  
C.J. Harland
Keyword(s):  
Surface Science ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Scanning Transmission ◽  
Low Energy Electrons ◽  
Electron Microscopes ◽  
A New Technique ◽  
Auger Microscopy ◽  
Electron Imaging ◽  
Analytic Signals

Low energy electrons, in the energy range 0-2 keV, are very useful in surface science. Both secondary (0-100 eV nominally) and Auger (50-2 keV) electrons can be used as analytic signals in ultra-high vacuum (UHV) scanning (SEM) and scanning transmission (STEM) electron microscopes. This paper briefly reviews some ongoing projects, which are aimed at improving the spatial resolution and information content of these signals.Both secondary electron imaging (SEI) and Auger electrons spectroscopy (AES) have a long history. Reviews of AES and its microscopic counterpart scanning Auger microscopy (SAM) have been given previously in this International Conference Series; over the intervening period AES/SAM instruments have become widely available commercially. Simply biassing the sample up to a few hundred volts (-ve) has lead to a new technique (biassed-SEI) which is sensitive at the sub-monolayer level. In general biassing the sample is a useful additional experimental variable. It can be used to visualize thin films and surface topography, including steps; it can also be used to distinguish spectral features (eg Auger peaks) from the sample from those due to stray electrons, and to place such features in the best energy region for the electron spectrometer.

Electron diffraction in UHV SEM, REM, and TEM

1994 ◽  
Vol 52 ◽  
pp. 594-595
Author(s):  
J. A. Venables ◽  
C. J. Harland ◽  
P. A. Bennett ◽  
T. E. A. Zerrouk
Keyword(s):  
Electron Diffraction ◽  
Surface Science ◽  
Incidence Angle ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Local Structures ◽  
Surface Reconstructions ◽  
Adsorbed Atoms ◽  
Low Energy Electron ◽  
Electron Microscopes

Electron diffraction techniques are widely used in Surface Science, with the main aim of determining atomic positions in surface reconstructions and the location of adsorbed atoms. These techniques require an Ultra-high vacuum (UHV) environment. The use of a focussed beam in UHV electron microscopes in principle allows such techniques to be applied on a microscopic scale. Most obviously this has been achieved in the Low Energy Electron Microscope (LEEM), where the corresponding diffraction technique, LEED, can now be used to investigate local areas with different surface structures, and to follow both temperature and time evolution of these local structures. Some other geometries can be used to achieve similar goals. If the incident energy is raised, the incidence angle has to be moved from normal towards glancing, so that the 'perpendicular' energy is kept within the LEED range of 10-100 eV. Several reflection (REM) and scanning (SEM) instruments have been built with energies between 5 and lOOkeV. In general, the addition of RHEED to an UHV-SEM with Auger Electron Spectroscopy (AES) forms a very useful tool in Surface Science.

Microstructures of Si(111) on Ion Sputtering and Electron Annealing

1991 ◽  
Vol 236 ◽  
Author(s):  
R. Al ◽  
T. S. Savage ◽  
P. Xu ◽  
J. P. Zhang ◽  
L. D. Marks
Keyword(s):  
Sample Preparation ◽  
Surface Science ◽  
Microstructure Evolution ◽  
Preparation Method ◽  
Ion Beam ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Ion Beam Sputtering ◽  
Transmission Electron ◽  
Beam Sputtering

AbstractThe microstructure evolution during preparation of thin Si(111) samples for surface sensitive imaging has been studied using ultra-high vacuum (UHV) transmission electron microscopy (TEM). The effects of ion beam sputtering and electron annealing have been investigated. A unique and routine sample preparation method for surface sensitive TEM imaging that combines TEM sample preparations with surface science sample preparation was developed. The microstructure evolution during the sample preparation process was studied in detail.

Surface Structures and Rearrangements in Oxides

1990 ◽  
Vol 183 ◽  
Author(s):  
M. R. Mccartney ◽  
David J. Smith
Keyword(s):  
High Resolution ◽  
Electron Irradiation ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Electron Dose ◽  
Dose Rates ◽  
Resolution Electron ◽  
Resolution Imaging ◽  
Current Densities ◽  
Electron Microscopes

AbstractElectron-beam-induced surface reactions and rearrangements have been observed for a number of oxides including MgO, TiO2, SrTiO3 and SnO2 using conventional and ultra-high-vacuum high-resolution electron microscopes. Electron irradiation of TiO2 resulted in a variety of effects including reduction, re-oxidation and amorphization. SnO2 was observed to form facets readily during high-resolution imaging but it was stable against reduction except when exposed to extreme current densities which caused the formation of metallic tin crystals. Electron irradiation of MgO under UHV conditions resulted in the formation of facetted pits. The surfaces of SrTiO3 were stable for moderate electron dose rates but rapidly amorphized when irradiated at extreme current densities.

Atomic-level imaging of the surface structure of Ag2O

1984 ◽  
Vol 42 ◽  
pp. 656-657
Author(s):  
William Krakow
Keyword(s):  
High Vacuum ◽  
Atomic Level ◽  
Ultra High Vacuum ◽  
Research Groups ◽  
Resolution Electron ◽  
Surface Reconstructions ◽  
Order Of Magnitude ◽  
High Resolution Electron Microscope ◽  
Saturated Structure ◽  
Transmission And Reflection

In recent years electron microscopy has been used to image surfaces in both the transmission and reflection modes by many research groups. Some of this work has been performed under ultra high vacuum conditions (UHV) and apparent surface reconstructions observed. The level of resolution generally has been at least an order of magnitude worse than is necessary to visualize atoms directly and therefore the detailed atomic rearrangements of the surface are not known. The present author has achieved atomic level resolution under normal vacuum conditions of various Au surfaces. Unfortunately these samples were exposed to atmosphere and could not be cleaned in a standard high resolution electron microscope. The result obtained surfaces which were impurity stabilized and reveal the bulk lattice (1x1) type surface structures also encountered by other surface physics techniques under impure or overlayer contaminant conditions. It was therefore decided to study a system where exposure to air was unimportant by using a oxygen saturated structure, Ag2O, and seeking to find surface reconstructions, which will now be described.

A theory of contamination in electron microscopes by surface diffusion

1978 ◽  
Vol 36 (1) ◽  
pp. 116-117
Author(s):  
J.T. Fourie
Keyword(s):  
Electron Beam ◽  
Surface Diffusion ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Physical Parameters ◽  
Carbon Compounds ◽  
Hydrocarbon Molecules ◽  
Electron Microscopes ◽  
Primary Electrons ◽  
Long Chain

Contamination in electron microscopes can be a serious problem in STEM or in situations where a number of high resolution micrographs are required of the same area in TEM. In modern instruments the environment around the specimen can be made free of the hydrocarbon molecules, which are responsible for contamination, by means of either ultra-high vacuum or cryo-pumping techniques. However, these techniques are not effective against hydrocarbon molecules adsorbed on the specimen surface before or during its introduction into the microscope. The present paper is concerned with a theory of how certain physical parameters can influence the surface diffusion of these adsorbed molecules into the electron beam where they are deposited in the form of long chain carbon compounds by interaction with the primary electrons.

Modifications of a JEOL 2000EX TEM for insSitu surface studies

1993 ◽  
Vol 51 ◽  
pp. 640-641
Author(s):  
Michael T. Marshall ◽  
Xianghong Tong ◽  
J. Murray Gibson
Keyword(s):  
Electron Diffraction ◽  
Surface Science ◽  
Film Growth ◽  
High Vacuum ◽  
High Energy ◽  
Energy Electron ◽  
Ultra High Vacuum ◽  
Transmission Electron ◽  
Fundamental Insight

We have modified a JEOL 2000EX Transmission Electron Microscope (TEM) to allow in-situ ultra-high vacuum (UHV) surface science experiments as well as transmission electron diffraction and imaging. Our goal is to support research in the areas of in-situ film growth, oxidation, and etching on semiconducter surfaces and, hence, gain fundamental insight of the structural components involved with these processes. The large volume chamber needed for such experiments limits the resolution to about 30 Å, primarily due to electron optics. Figure 1 shows the standard JEOL 2000EX TEM. The UHV chamber in figure 2 replaces the specimen area of the TEM, as shown in figure 3. The chamber is outfitted with Low Energy Electron Diffraction (LEED), Auger Electron Spectroscopy (AES), Residual Gas Analyzer (RGA), gas dosing, and evaporation sources. Reflection Electron Microscopy (REM) is also possible. This instrument is referred to as SHEBA (Surface High-energy Electron Beam Apparatus).The UHV chamber measures 800 mm in diameter and 400 mm in height. JEOL provided adapter flanges for the column.

scholarly journals The Growth of Semiconductor Thin Films Studied by RHEED

1990 ◽  
Vol 43 (5) ◽  
pp. 583
Author(s):  
GL Price
Keyword(s):  
Thin Films ◽  
Surface Science ◽  
High Vacuum ◽  
High Energy ◽  
Ultra High Vacuum ◽  
Large Area ◽  
Growth Modes ◽  
Semiconductor Thin Films ◽  
Wide Range ◽  
Recent Developments

Recent developments in the growth of semiconductor thin films are reviewed. The emphasis is on growth by molecular beam epitaxy (MBE). Results obtained by reflection high energy electron diffraction (RHEED) are employed to describe the different kinds of growth processes and the types of materials which can be constructed. MBE is routinely capable of heterostructure growth to atomic precision with a wide range of materials including III-V, IV, II-VI semiconductors, metals, ceramics such as high Tc materials and organics. As the growth proceeds in ultra high vacuum, MBE can take advantage of surface science techniques such as Auger, RHEED and SIMS. RHEED is the essential in-situ probe since the final crystal quality is strongly dependent on the surface reconstruction during growth. RHEED can also be used to calibrate the growth rate, monitor growth kinetics, and distinguish between various growth modes. A major new area is lattice mismatched growth where attempts are being made to construct heterostructures between materials of different lattice constants such as GaAs on Si. Also described are the new techniques of migration enhanced epitaxy and tilted superlattice growth. Finally some comments are given On the means of preparing large area, thin samples for analysis by other techniques from MBE grown films using capping, etching and liftoff.

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