II-VI Semiconductor Heterostructures: Pointers to Appropriate Analysis Techniques

1990 ◽  
Vol 216 ◽  
Author(s):  
Erica G. Bithell
Keyword(s):  
Dark Field ◽  
Semiconductor Heterostructures ◽  
Alternative Methods ◽  
Composition Change ◽  
Bright Field ◽  
Approximate Methods ◽  
Analysis Techniques ◽  
Transmission Electron ◽  
Quantitative Characterisation ◽  
Microscopy Techniques

ABSTRACTApproximate methods are used, for a variety of II–VI semiconductor alloys, to estimate the sensitivity to composition change of quantitative transmission electron microscopy techniques which have proved successful in characterising III–V heterostructures. It is shown that bright field thickness fringe matching at the [001] axis is likely to prove relatively more successful than 200 dark field intensity measurement for many alloy systems. It is also noted that alternative methods would be necessary if quantitative characterisation of (Mn,Zn) compounds were required.

Interlayer mixing in GaAs/AlxGa1-xAs heterostructures as a result of Se+ ion implantation

1988 ◽  
Vol 46 ◽  
pp. 908-909
Author(s):  
E.G. Bithell ◽  
W.M. Stobbs
Keyword(s):  
Ion Implantation ◽  
Diffusion Coefficients ◽  
Dark Field ◽  
Atomic Mass ◽  
Composition Profile ◽  
Semiconductor Heterostructures ◽  
Transmission Electron ◽  
Microscope Images ◽  
Damage Process ◽  
Electron Energy Loss

It is well known that the microstructural consequences of the ion implantation of semiconductor heterostructures can be severe: amorphisation of the damaged region is possible, and layer intermixing can result both from the original damage process and from the enhancement of the diffusion coefficients for the constituents of the original composition profile. A very large number of variables are involved (the atomic mass of the target, the mass and energy of the implant species, the flux and the total dose, the substrate temperature etc.) so that experimental data are needed despite the existence of relatively well developed models for the implantation process. A major difficulty is that conventional techniques (e.g. electron energy loss spectroscopy) have inadequate resolution for the quantification of any changes in the composition profile of fine scale multilayers. However we have demonstrated that the measurement of 002 dark field intensities in transmission electron microscope images of GaAs / AlxGa1_xAs heterostructures can allow the measurement of the local Al / Ga ratio.

Techniques for Characterising Artificial Layer Structures using Transmission Electron Microscopy

1987 ◽  
Vol 103 ◽  
Author(s):  
W. M. Stobbs
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Structural Changes ◽  
Dark Field ◽  
Multilayer Structures ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Layer Structures ◽  
Quantitative Characterisation ◽  
Field Imaging

ABSTRACTT.E.M. methods are described for the quantitative characterisation of the compositional and structural changes at interfaces and in homo- and hetero-phase multilayer structures. Many of the newer approaches described including the Fresnel and Centre Stop Dark Field Imaging Methods were developed specifically for such characterisations. The range of applications of each of the techniques is assessed as is the importance of delineating the limiting effects of inelastic and inelastic/elastic multiple scattering.

Electron Irradiation and Electron Tomography Studies of Glasses and Glass Nanocomposites

2008 ◽  
Vol 1107 ◽  
Author(s):  
G. Möbus ◽  
G. Yang ◽  
Z. Saghi ◽  
X. Xu ◽  
R.J. Hand ◽  
...  
Keyword(s):  
Fine Structure ◽  
Electron Tomography ◽  
Dark Field ◽  
Gradual Transition ◽  
Borosilicate Glasses ◽  
Redox Partner ◽  
Transmission Electron ◽  
Annular Dark Field ◽  
Microscopy Techniques ◽  
Electron Energy Loss

AbstractCharacterization of glasses and glass nanocomposites using modern transmission electron microscopy techniques is demonstrated. Techniques used include: (i) high-angle-annular dark field STEM for imaging of nanocomposites, (ii) electron tomography for 3D reconstruction and quantification of nanoparticle volume fractions, and (iii) fine structure electron energy loss spectroscopy for evaluation of boron coordination. Precipitation of CeO2nanoparticles in borosilicate glasses is examined as a function of glass composition and redox partner elements. A large increase in the solubility of Ce is found for compositions where Ce retains +IV valence in the glass. Irradiation experiments with electrons and λ-rays are summarized and the degree of damage is compared by using changes in the boron K-edge fine structure, which allows the gradual transition from BO4to BO3coordination to be followed.

An Inexpensive Approach for Bright-Field and Dark-Field Imaging by Scanning Transmission Electron Microscopy in Scanning Electron Microscopy

2014 ◽  
Vol 20 (1) ◽  
pp. 124-132 ◽  
Author(s):  
Binay Patel ◽  
Masashi Watanabe
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Scanning Transmission Electron Microscopy ◽  
Lattice Spacing ◽  
Dark Field ◽  
Bright Field ◽  
Specimen Holder ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Scanning Electron

AbstractScanning transmission electron microscopy in scanning electron microscopy (STEM-in-SEM) is a convenient technique for soft materials characterization. Various specimen-holder geometries and detector arrangements have been used for bright-field (BF) STEM-in-SEM imaging. In this study, to further the characterization potential of STEM-IN-SEM, a new specimen holder has been developed to facilitate direct detection of BF signals and indirect detection of dark-field (DF) signals without the need for substantial instrument modification. DF imaging is conducted with the use of a gold (Au)-coated copper (Cu) plate attached to the specimen holder which directs highly scattered transmitted electrons to an off-axis yttrium-aluminum-garnet (YAG) detector. A hole in the copper plate allows for BF imaging with a transmission electron (TE) detector. The inclusion of an Au-coated Cu plate enhanced DF signal intensity. Experiments validating the acquisition of true DF signals revealed that atomic number (Z) contrast may be achieved for materials with large lattice spacing. However, materials with small lattice spacing still exhibit diffraction contrast effects in this approach. The calculated theoretical fine probe size is 1.8 nm. At 30 kV, in this indirect approach, DF spatial resolution is limited to 3.2 nm as confirmed experimentally.

A Weak-Beam Dark-Field Study of Stacking Faults in a Co-Cr-Mo-C Alloy

1976 ◽  
Vol 34 ◽  
pp. 378-379
Author(s):  
Ernest L. Hall
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Field Study ◽  
Previous Investigation ◽  
Stacking Faults ◽  
Aging Treatment ◽  
Dark Field ◽  
Bright Field ◽  
Weak Beam ◽  
Transmission Electron

In a previous investigation (1) of the mechanisms of strengthening in a Co-28 wt% Cr-6 wt% Mo-0.29 wt% C alloy (H.S. 21), it was observed that the fee regions of this alloy were generally heavily faulted, and the density of stacking faults was seen to be dependent upon the time and temperature of the aging treatment after solutionizing. In the present study, weak-beam darkfield transmission electron microscopy was used to examine the interaction of stacking faults on intersecting {111} planes. The alloy was solutionized at 1230°C for 4 hours, quenched in water, and aged at 650°C for 8 hours in order to produce a suitable density of faults. Figure 1 shows a bright-field (BF), weak-beam dark-field (WB DF) pair of micrographs illustrating both the successful and unsuccessful intersection of faults which exist in different ﹛111﹜ planes.

Dislocation contrast in high-angle hollow-cone dark-field TEM

1993 ◽  
Vol 51 ◽  
pp. 694-695
Author(s):  
Z. L. WANG
Keyword(s):  
Strong Dependence ◽  
Dark Field ◽  
Diffraction Reflection ◽  
High Angle ◽  
Hollow Cone ◽  
Bright Field ◽  
Transmission Electron ◽  
Set Up ◽  
The One ◽  
Dramatic Variation

Dislocations were imaged using the high-angle hollow-cone dark-field transmission electron microscopy (HADF-TEM) technique. Experiments were performed using a Philips CM30 TEM at 300 kV Dislocations and grain boundaries show bright contrast in HADF-TEM images and there are no contrast reversals with thickness or defocus. The dislocation contrast shows no dramatic variation when the average semi-conical angle θ was increased from 40 to 110 mrad, but does show strong dependence on the diffracting conditions that are set up for the corresponding on-axis bright-field (BF) TEM image (Fig. 1). Under the "one-beam" (random orientation without strong diffraction) reflection condition (Figs, 1a and 1a'), the visibility of the dislocations is poor in either the BF-TEM or the HADF-TEM image. Under the two-beam diffracting condition (Figs, 1b and 1b') both BF-TEM and HADF-TEM images show optimized contrast. The features appearing in the HADF-TEM images have a good one-to-one correspondence with the features shown in the corresponding BF-TEM images; the dislocation contrast disappears in the HADF-TEM images if the condition g·b = 0 is satisfied in the BF-TEM images, where b is the Burgers vector (Fig 2).

Stacking faults in uranium dioxide

1964 ◽  
Vol 280 (1380) ◽  
pp. 37-46 ◽  
Keyword(s):  
Uranium Dioxide ◽  
Fault Plane ◽  
Displacement Vector ◽  
Stacking Faults ◽  
Dark Field ◽  
Stacking Fault ◽  
Arc Furnace ◽  
Bright Field ◽  
Transmission Electron ◽  
Bright Field Microscopy

Specimens of uranium dioxide have been quenched in an arc furnace from temperatures just below the melting point, cut into slices and chemically thinned for examination by transmission electron microscopy. Defects in the form of stacking faults and tetrahedra have been observed. Complete contrast experiments have been successfully carried out on some of these stacking faults and reveal a 1/6[1͞21] displacement vector lying in the fault plane. (Ill) and (201) stacking fault planes have been identified and it is thought that many more stacking fault planes exist having the displacement vector as zone axis. A combination of dark-field and bright-field microscopy shows that the faults are intrinsic. The tetrahedra are thought to be stacking faults lying on all four {111} planes and are attributed to dissociation of Frank sessile loops formed by vacancy condensation on {111} planes.

Instrumental developments for electron microscopes: A STEM detector and correctors for a LVSEM and a 200 kV TEM

1993 ◽  
Vol 51 ◽  
pp. 624-625
Author(s):  
Max Haider
Keyword(s):  
Scanning Transmission Electron Microscopy ◽  
Phase Contrast ◽  
Dark Field ◽  
Processing Unit ◽  
High Angle ◽  
Bright Field ◽  
Scattering Angle ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Electron Microscopes

One advantage of scanning transmission electron microscopy (STEM) over conventional TEM which is often cited is the capability to simultaneously record the various scattered electrons with properly designed detectors. So far, this advantage has only been utilized to record bright-field or inelastic and dark-field (low and high angle) images in parallel. However, it has not been used to record all transmitted electrons separately according to their scattering angle. We developed a flexible multichannel detector system based on a silicon chip which has been fabricated to our specifications. This detector consists of 30 rings which are split into 4 quadrants (see Fig. 1), and is operated in an electron counting mode. The rings can be used to separate the electrons according to their scattering angle for low and high angle dark-field images, to obtain the various phase-contrast images and to normalize the signals by the sum of all detectors. The system records the signals of the 120 channels in parallel and the counts of each channel can be combined in an integer processing unit in order to form 8 different images.

Identifying Hexagonal Boron Nitride Monolayers by Transmission Electron Microscopy

2012 ◽  
Vol 18 (3) ◽  
pp. 558-567 ◽  
Author(s):  
Michael L. Odlyzko ◽  
K. Andre Mkhoyan
Keyword(s):  
Boron Nitride ◽  
Hexagonal Boron Nitride ◽  
Dark Field ◽  
Zone Axis ◽  
Bright Field ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Annular Dark Field ◽  
Stem Image ◽  
Tilt Series

AbstractMultislice simulations in the transmission electron microscope (TEM) were used to examine changes in annular-dark-field scanning TEM (ADF-STEM) images, conventional bright-field TEM (BF-CTEM) images, and selected-area electron diffraction (SAED) patterns as atomically thin hexagonal boron nitride (h-BN) samples are tilted up to 500 mrad off of the [0001] zone axis. For monolayer h-BN the contrast of ADF-STEM images and SAED patterns does not change with tilt in this range, while the contrast of BF-CTEM images does change; h-BN multilayer contrast varies strongly with tilt for ADF-STEM imaging, BF-CTEM imaging, and SAED. These results indicate that tilt series analysis in ADF-STEM image mode or SAED mode should permit identification of h-BN monolayers from raw TEM data as well as from quantitative post-processing.

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