Quantitative Measurement of Compositional Enrichment in Strained Alloy Quantum Dots

2001 ◽  
Vol 7 (S2) ◽  
pp. 218-219
Author(s):  
P.A. Crozier ◽  
M. Catalano
Keyword(s):  
Quantum Dots ◽  
Energy Loss ◽  
Electron Energy ◽  
Vision System ◽  
Wetting Layer ◽  
Spatially Resolved ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Alloy Quantum Dots ◽  
Electron Energy Loss

High spatial resolution information on the structure and composition of semiconductor quantum dots is necessary to relate microstructure to macroscopic electron-optical properties [1]. Scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS) can be used to determine the elemental composition of nanometer-sized particles. Applying these techniques to quantum dots is challenging because the dot nucleates on a very thin wetting layer of similar composition and is embedded in a matrix. Here we present a strategy to extract absolute compositional information on InGaAs dots. The method relies on modeling both the dot shape and the electron probe profile.Samples were prepared by depositing four monolayers of In0.5Ga0.5As onto a GaAs substrate giving a nominal wetting layer thickness of 1.2 nm [2]. STEM was performed on a Vacuum Generator's HB501 equipped with a GATAN parallel electron energy-loss spectrometer. An ES Vision system was used to acquire spatially resolved electron energy-loss spectra from the wetting layer and the quantum dots.

Analysis of AlxGa1-xN nanowires through simulated methods of scanning transmission electron microscopy and electron energy-loss spectroscopy

2013 ◽  
Vol 6 (1) ◽  
Author(s):  
R. Kumar ◽  
P.J. Phillips ◽  
R.F. Klie
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Scanning Transmission Electron Microscopy ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Electron Energy Loss

AlxGa1-xN nanowires have promising applications in ultraviolet light emitting diodes (LEDs). However, these nanowires are not typical p-n junction semiconductors, but rather rely on varying concentrations of Al versus Ga to produce electron hole pairs. More information on the atomic structure is needed to better understand the properties of these nanowires. In this study, AlxGa1-xN nanowires were imaged using scanning transmission electron microscopy (STEM) and compared to computer simulated STEM images to obtain physical information on the nanowires. Electron energy-loss spectroscopy (EELS) and FEFF9 computer simulations were also performed to better understand the structural and chemical properties of the nanowires. Results from these simulations showed that changes in the chemical ordering of the nanowires were responsible for changes in intensity and resolution in the images. These intensity and resolution trends were not a result of interface effects. This will help to further characterize nanowires in the future.

Electron Energy Loss in Membrane Components: Possibilities of Contrast and Identification in the STEM

1975 ◽  
Vol 33 ◽  
pp. 506-507
Author(s):  
J. Hainfeld ◽  
M. Isaacson
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Uv Light ◽  
Distinct Advantage ◽  
Chemical Compositions ◽  
Molecular Architecture ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Membrane Components ◽  
Electron Energy Loss

It is well known that the energy loss spectra of fast electrons transmitted through thin specimens may he employed to analyze the material through which they have passed. Therefore, in principle, electrons can be used in a similar manner as one uses UV light to probe the chemical compositions of a specimen. The distinct advantage, of course, is the potential capability of utilizing the electron microscope for identifying compounds with microscopic spatial resolution (see, for example, Ref. 1). In biological membranes, for example, there thus exists the possibility of distinguishing proteins, phospholipids, cholesterol and carbohydrates on the basis of their electron energy loss spectra. This could be of value in delineating the twodimensional molecular architecture of membranes. We have therefore undertaken a program to determine the extent to which energy loss electrons can be useful in the scanning transmission electron microscopy of membranes.

ELECTRON ENERGY LOSS SPECTROSCOPY AND ANNULAR DARK FIELD IMAGING AT A NANOMETER RESOLUTION IN A SCANNING TRANSMISSION ELECTRON MICROSCOPE

2000 ◽  
Vol 07 (04) ◽  
pp. 475-494 ◽  
Author(s):  
O. STÉPHAN ◽  
A. GLOTER ◽  
D. IMHOFF ◽  
M. KOCIAK ◽  
C. MORY ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Energy Loss ◽  
Electron Energy ◽  
Transmission Electron Microscope ◽  
Electron Energy Loss Spectroscopy ◽  
Scanning Transmission Electron Microscope ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Electron Energy Loss

The basics of electron energy loss spectroscopy (EELS) performed in the context of a scanning transmission electron microscope are described. This includes instrumentation, information contained in an EELS spectrum, data acquisition and processing, and some illustrations by a few examples.

SiO2 Formation at the Aluminum Oxide/Si(100) Interface

2002 ◽  
Vol 747 ◽  
Author(s):  
A. Roy Chowdhuri ◽  
C. G. Takoudis ◽  
R. F. Klie ◽  
N. D. Browning
Keyword(s):  
Electron Microscope ◽  
Aluminum Oxide ◽  
Energy Loss ◽  
Electron Energy ◽  
Transmission Electron Microscope ◽  
Scanning Transmission Electron Microscope ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Z Contrast ◽  
Electron Energy Loss

ABSTRACTThin films of aluminum oxide were deposited on clean Si(100) substrates using trimethylaluminum and oxygen at 300°C. Infrared spectroscopic and x-ray photoelectron spectroscopic analyses of these films showed no aluminum silicate or SiO2 phase formation at the film/substrate interface. The O/Al ratio in the as deposited film was found to be higher than that in stoichiometric Al2O3. On annealing the as deposited samples in Ar at higher temperatures, a peak due to the transverse optical phonon for the Si-O-Si stretching mode appeared in the infrared spectra. A combination of Z-contrast imaging and electron energy loss spectroscopy in the scanning transmission electron microscope confirmed that the annealed samples developed a layer of silicon dioxide at the aluminum oxide-Si interface. Z-contrast images and electron energy loss spectra, obtained while heating the sample inside the scanning transmission electron microscope were used to follow the interfacial SiO2 formation.

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