μm-Scale Lateral Growth of Ga-Monolayers Observed In-Situ by Electron Microscopy

1989 ◽  
Vol 159 ◽  
Author(s):  
J. Osaka ◽  
N. Inoue
Keyword(s):  
Electron Microscopy ◽  
Secondary Electron ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Intensity Difference ◽  
Lateral Growth ◽  
Mbe Growth ◽  
Electron Intensity ◽  
Scanning Electron

ABSTRACTAn ultra high vacuum scanning electron microscope equipped to an MBE system is utilized to study a transient of a surface atomic structure during MBE growth of GaAs and AlGaAs by the alternate supply method. Lateral growth of a Ga-monolayer over microns is realized utilizing Ga droplets. This is confirmed by discriminating the Ga and As top layer by using the secondary electron intensity difference between the Ga and As top layer. The growth mechanism of the Ga monolayer is discussed based on the results.

Transmission Electron Microscopy of Epitaxial silicides grown by ultra high vacuum deposition

1989 ◽  
Vol 47 ◽  
pp. 462-463
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
High Vacuum ◽  
High Energy ◽  
Energy Electron ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Transmission Electron

The silicides CoSi2 and NiSi2 are both metallic with the fee flourite structure and lattice constants which are close to silicon (1.2% and 0.6% smaller at room temperature respectively) Consequently epitaxial cobalt and nickel disilicide can be grown on silicon. If these layers are formed by ultra high vacuum (UHV) deposition (also known as molecular beam epitaxy or MBE) their thickness can be controlled to within a few monolayers. Such ultrathin metal/silicon systems have many potential applications: for example electronic devices based on ballistic transport. They also provide a model system to study the properties of heterointerfaces. In this work we will discuss results obtained using in situ and ex situ transmission electron microscopy (TEM).In situ TEM is suited to the study of MBE growth for several reasons. It offers high spatial resolution and the ability to penetrate many monolayers of material. This is in contrast to the techniques which are usually employed for in situ measurements in MBE, for example low energy electron diffraction (LEED) and reflection high energy electron diffraction (RHEED), which are both sensitive to only a few monolayers at the surface.

The Energy Spectra of Secondary Electrons

2000 ◽  
Vol 6 (S2) ◽  
pp. 750-751
Author(s):  
David C Joy ◽  
David Braski
Keyword(s):  
Surface Layer ◽  
Electron Microscope ◽  
Secondary Electron ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Energy Spectra ◽  
Yield Coefficient ◽  
Sem Images ◽  
Secondary Electrons ◽  
Scanning Electron

It has been estimated that more than 90% of all scanning electron microscope (SEM) images ever published have been obtained using secondary electrons (SE) which are defined as being those electrons emitted with energies between 0 and 50eV. The properties of these secondary electron are therefore of considerable interest and importance. However, although secondary electrons have been intensively studied since their discovery by Starke in 1901 the majority of the work has been aimed at determining the SE yield coefficient and its variation with energy for elements and compounds. The energy spectrum of secondary electrons has received far less attention although it is evident that the form of the spectrum must have an effect on the image contrast observed in the SEM because SE detectors are energy selective devices. The few studies that have been made have mostly concentrated on spectra obtained from clean samples observed under ultra-high vacuum conditions. This is understandable, because it is certain that the presence of a surface layer of contamination will change the SE spectrum to some degree or other, but it is unfortunate because all specimens in real SEMs are dirty and it is information about this situation that is required.

In Situ Electron Microscopy Studies of Surface Dynamical Processes

1998 ◽  
Vol 4 (S2) ◽  
pp. 608-609
Author(s):  
Ruud M. Tromp
Keyword(s):  
Electron Microscopy ◽  
Strain Relaxation ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Relaxation Phase ◽  
Transmission Electron ◽  
In Situ Electron Microscopy ◽  
Low Energy Electron ◽  
New Machine

To obtain a full and detailed understanding of the spatiotemporal dynamics of surface processes such as epitaxial growth, strain relaxation, phase transformations and phase transitions, chemisorption and etching, in situ real-time observations have proven to be invaluable. The development of two experimental techniques, i.e. Low Energy Electron Microscopy (LEEM) typically operating at electron energies below 10 eV, and Ultra-High-Vacuum Transmission Electron Microscopy (UHV-TEM) at several 100 keV, has made such in situ studies routinely possible. In many cases, the videodata obtained from such experiments are amenable to detailed, quantitative analysis, yielding statistical, kinetic and thermodynamic information that cannot be obtained in any other way.I will discuss recent experimental developments, including the design and construction of a new and improved LEEM instrument. Figure 1 shows a schematic diagram of this new machine. There are several features that distinguishes this design from most other LEEMs. One is the use of a 90 degree deflection magnetic prism array,

The Origins of High Spatial Resolution Secondary Electron Microscopy

1992 ◽  
Vol 295 ◽  
Author(s):  
M. R. Scheinfein ◽  
J. S. Drucker ◽  
J. Liu ◽  
J. K. Weiss ◽  
G. G. Hembree ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Spatial Resolution ◽  
Secondary Electron ◽  
High Spatial Resolution ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Generation Process ◽  
Secondary Electrons ◽  
Electron Generation ◽  
Secondary Electron Generation

AbstractThe secondary electron generation process is studied in an ultra-high vacuum scanning transmission electron microscope using electron coincidence spectroscopy. Production pathways for secondary electrons are determined by analyzing coincidences between secondary electrons and individual excitation events. The ultimate spatial resolution available in scanning electron microscopy is limited by the delocalization of the secondary electron generation process. This delocalization is studied using momentum resolved coincidence electron spectroscopy. The fraction of secondary electrons resulting from localized excitations can explain the high spatial resolution observed in secondary electron microscopy images.

Secondary Electron Emission Contrast of Quantum Wells in GaAs p-i-n Junctions

2009 ◽  
Vol 15 (2) ◽  
pp. 125-129 ◽  
Author(s):  
Enrique Grunbaum ◽  
Zahava Barkay ◽  
Yoram Shapira ◽  
Keith W.J. Barnham ◽  
David B. Bushnell ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Quantum Wells ◽  
Electron Emission ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
Contrast Mechanisms ◽  
Novel Method ◽  
Profile Changes ◽  
Scanning Electron

AbstractThe secondary electron (SE) signal over a cleaved surface of GaAs p-i-n solar cells containing stacks of quantum wells (QWs) is analyzed by high-resolution scanning electron microscopy. The InGaAs QWs appear darker than the GaAsP barriers, which is attributed to the differences in electron affinity. This method is shown to be a powerful tool for profiling the conduction band minimum across junctions and interfaces with nanometer resolution. The intrinsic region is shown to be pinned to the Fermi level. Additional SE contrast mechanisms are discussed in relation to the dopant regions themselves as well as the AlGaAs window at the p-region. A novel method of in situ observation of the SE profile changes resulting from reverse biasing these structures shows that the built-in potential may be deduced. The obtained value of 0.7 eV is lower than the conventional bulk value due to surface effects.

scholarly journals Surface Kinetics of Copper Oxidation Investigated by In Situ Ultra-high Vacuum Transmission Electron Microscopy

2001 ◽  
Vol 7 (6) ◽  
pp. 486-493 ◽  
Author(s):  
Judith C. Yang ◽  
Mridula D. Bharadwaj ◽  
Guangwen Zhou ◽  
Lori Tropia
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Water Vapor ◽  
High Vacuum ◽  
Quantitative Model ◽  
Ultra High Vacuum ◽  
Copper Oxidation ◽  
Initial Oxidation ◽  
Transmission Electron

AbstractWe review our studies of the initial oxidation stages of Cu(001) thin films as investigated by in situ ultra-high vacuum transmission electron microscopy. We present our observations of surface reconstruction and the nucleation to coalescence of copper oxide during in situ oxidation in O2. We have proposed a semi-quantitative model, where oxygen surface diffusion is the dominant mechanism of the initial oxidation stages of Cu. We have also investigated the effect of water vapor on copper oxidation. We have observed that the presence of water vapor in the oxidizing atmosphere retards the rate of Cu oxidation and Cu2O is reduced when exposed directly to steam.

The Performance of a Thermal Field Emission Gun

1975 ◽  
Vol 33 ◽  
pp. 146-147
Author(s):  
Dennis M. Maher ◽  
David C. Joy
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Field Emission ◽  
Thermal Field ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Magnetic Alignment ◽  
Stable Operation ◽  
Alignment System ◽  
Scanning Electron

Although the "cold" field emission gun has been used successfully for both transmission and scanning electron microscopy it requires ultra-high vacuum which is not obtained easily when such a gun is interfaced to a conventional microscope system. Recently, the "thermal" field emission gun (TFEG) in which the emitting tip is held at around 1700°K has been proposed as an alternative electron source for such applications. Under this condition the tip is cleaned continuously, and surface asperities are smoothed, therefore stable operation is possible in a high vacuum. In this paper we report on the build-up characteristics, current stability and brightness of a TFEG which has been interfaced to a JEOL JEM 100B microscope equipped with a scanning attachment. The gun consists of a (111) tungsten emitter set on a rhenium filament, three anodes and a two stage magnetic alignment system. The gun chamber is ion pumped to a pressure in the range 6xl0-8 to 2xl0-9 torr.

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