Behavior of Metastable Te Donor Concentrations in Q-Switched Ruby Laser Annealed GaAs

1980 ◽  
Vol 1 ◽  
Author(s):  
P. Pianetta ◽  
J. Amano ◽  
G. Woolhouse ◽  
C. A. Stolte
Keyword(s):  
Electron Microscopy ◽  
Activation Energy ◽  
Transmission Electron Microscopy ◽  
Ruby Laser ◽  
Structural Changes ◽  
The Other ◽  
Dislocation Loops ◽  
Transmission Electron ◽  
Half Angle ◽  
Laser Anneal

ABSTRACTThe thermal behavior of Te implanted, laser annealed GaAs was investigated by helium backscattering spectroscopy and transmission electron microscopy in order to correlate structural changes with the two stage reduction in the carrier concentration due to post laser anneal heating above 200°C. The activation energy for stage one which occurs in the range 200–400°C was determined to be approximately 1.3 eV. Post laser anneal heating at 450°C caused no observable structural changes. On the other hand, 850°C post laser anneal heating induced the formation of precipitates and dislocation loops as well as narrowing the channeling half-angle of Te by about 11%.

Ion Implant Activation and Redistribution in AlxGa1–xAs

1989 ◽  
Vol 157 ◽  
Author(s):  
S. J. Pearton ◽  
W. S. Hobson ◽  
A. E. Von Neida ◽  
N. M. Haegel ◽  
K. S. Jonesf ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Activation Energy ◽  
Transmission Electron Microscopy ◽  
Electrical Activity ◽  
Mole Fraction ◽  
Electrical Activation ◽  
Dislocation Loops ◽  
Rapid Annealing ◽  
Transmission Electron ◽  
Minimal Damage

ABSTRACTThe electrical activation characteristics of implanted Be, Mg, Si and S in AlxGa1–xAs (x = 0-1) were investigated as a function of ion dose for rapid annealing in the range 600-950°C. The apparent activation energy for electrical activity of these species increases with increasing AlAs mole fraction - for Be, the activation energy is 0.35eV for GaAs and 0.49eV for Al0.54Ga0.46 As. There is no evidence for pairing of Be and O in AlGaAs, in contrast to the situation for GaAs. Self-compensation is the predominant limiting mechanism for Si activation in AlGaAs as determined by the relative photoluminescence intensities of the SiGa-to-SiAs related transitions. No significant redistribution of implanted Si is observed for any AlAs mole fraction for rapid annealing (5 sec) up to 900°C, whereas S shows motion into the AlGaAs and no tendency to outdiffuse. By contrast, both Be and Mg display loss of the dopant to the surface, and little redistribution toward the bulk. Minimal damage is observed by transmission electron microscopy in as-implanted AlGaAs for Be or Si doses below the amorphization threshold. Upon annealing at the conditions for optimum activation, a high density of small dislocation loops is observed near the end of the ion range.

Embedding Procedure for Water Swollen Samples

1970 ◽  
Vol 28 ◽  
pp. 504-505
Author(s):  
Ann M. Thomas ◽  
Virginia Shemeley
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ion Exchange ◽  
Structural Changes ◽  
Cross Linking ◽  
Ion Exchange Resins ◽  
Transmission Electron ◽  
First Pass ◽  
Exchange Resins

Those samples which swell rapidly when exposed to water are, at best, difficult to section for transmission electron microscopy. Some materials literally burst out of the embedding block with the first pass by the knife, and even the most rapid cutting cycle produces sections of limited value. Many ion exchange resins swell in water; some undergo irreversible structural changes when dried. We developed our embedding procedure to handle this type of sample, but it should be applicable to many materials that present similar sectioning difficulties.The purpose of our embedding procedure is to build up a cross-linking network throughout the sample, while it is in a water swollen state. Our procedure was suggested to us by the work of Rosenberg, where he mentioned the formation of a tridimensional structure by the polymerization of the GMA biproduct, triglycol dimethacrylate.

Annealing Of Radiation Damage in Tungsten

1970 ◽  
Vol 28 ◽  
pp. 412-413
Author(s):  
Robert C. Rau ◽  
John Moteff
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Radiation Damage ◽  
Thermal Annealing ◽  
Neutron Fluence ◽  
Dislocation Loops ◽  
Defect Clusters ◽  
Polycrystalline Tungsten ◽  
Transmission Electron ◽  
Radiation Induced

Transmission electron microscopy has been used to study the thermal annealing of radiation induced defect clusters in polycrystalline tungsten. Specimens were taken from cylindrical tensile bars which had been irradiated to a fast (E > 1 MeV) neutron fluence of 4.2 × 1019 n/cm2 at 70°C, annealed for one hour at various temperatures in argon, and tensile tested at 240°C in helium. Foils from both the unstressed button heads and the reduced areas near the fracture were examined.Figure 1 shows typical microstructures in button head foils. In the unannealed condition, Fig. 1(a), a dispersion of fine dot clusters was present. Annealing at 435°C, Fig. 1(b), produced an apparent slight decrease in cluster concentration, but annealing at 740°C, Fig. 1(C), resulted in a noticeable densification of the clusters. Finally, annealing at 900°C and 1040°C, Figs. 1(d) and (e), caused a definite decrease in cluster concentration and led to the formation of resolvable dislocation loops.

Black-white contrast of dislocation loops

1978 ◽  
Vol 36 (1) ◽  
pp. 328-329
Author(s):  
J. J. Hren ◽  
W. D. Cooper ◽  
L. J. Sykes
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Dislocation Loops ◽  
Major Premise ◽  
Burgers Vector ◽  
Transmission Electron ◽  
Primary Means ◽  
Contrast Analysis ◽  
Dot Product ◽  
Imaging Conditions

Small dislocation loops observed by transmission electron microscopy exhibit a characteristic black-white strain contrast when observed under dynamical imaging conditions. In many cases, the topography and orientation of the image may be used to determine the nature of the loop crystallography. Two distinct but somewhat overlapping procedures have been developed for the contrast analysis and identification of small dislocation loops. One group of investigators has emphasized the use of the topography of the image as the principle tool for analysis. The major premise of this method is that the characteristic details of the image topography are dependent only on the magnitude of the dot product between the loop Burgers vector and the diffracting vector. This technique is commonly referred to as the (g•b) analysis. A second group of investigators has emphasized the use of the orientation of the direction of black-white contrast as the primary means of analysis.

scholarly journals Direct Characterization of the Relation between the Mechanical Response and Microstructure Evolution in Aluminum by Transmission Electron Microscopy In Situ Straining

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1431
Author(s):  
Seiichiro Ii ◽  
Takero Enami ◽  
Takahito Ohmura ◽  
Sadahiro Tsurekawa
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ion Beam ◽  
Elastic Behavior ◽  
Annealed Specimen ◽  
Displacement Curve ◽  
Dislocation Loops ◽  
Transmission Electron ◽  
Stress Drops

Transmission electron microscopy in situ straining experiments of Al single crystals with different initial lattice defect densities have been performed. The as-focused ion beam (FIB)-processed pillar sample contained a high density of prismatic dislocation loops with the <111> Burgers vector, while the post-annealed specimen had an almost defect-free microstructure. In both specimens, plastic deformation occurred with repetitive stress drops (∆σ). The stress drops were accompanied by certain dislocation motions, suggesting the dislocation avalanche phenomenon. ∆σ for the as-FIB Al pillar sample was smaller than that for the post-annealed Al sample. This can be considered to be because of the interaction of gliding dislocations with immobile prismatic dislocation loops introduced by the FIB. The reloading process after stress reduction was dominated by elastic behavior because the slope of the load–displacement curve for reloading was close to the Young’s modulus of Al. Microplasticity was observed during the load-recovery process, suggesting that microyielding and a dislocation avalanche repeatedly occurred, leading to intermittent plasticity as an elementary step of macroplastic deformation.

Ultrastructures of Epibiotic Suctorian, Tokophrya huangmeiensis 

Zootaxa ◽  
2018 ◽  
Vol 4521 (1) ◽  
pp. 145
Author(s):  
URFA BIN TAHIR ◽  
DENG QIONG ◽  
WANG ZHE ◽  
LI SEN ◽  
LIU YANG ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Light Microscopy ◽  
Structural Changes ◽  
Small Subunit ◽  
Free Living ◽  
Transmission Electron ◽  
Small Subunit Ribosomal Dna ◽  
Ribosomal Dna Sequence ◽  
Freshwater Ciliates

Tokophrya species are either free-living or facultative ectosymbiotic suctorians associated with copepods, isopods, mysids, decapods and amphipods. Tokophrya huangmeiensis in particular is found to be epizoic with the redclaw crayfish Cherax quadricarinatus Von Martens, 1868, which has been observed as part of an ongoing investigation of freshwater ciliates biodiversity in Huanggang, Hubei, China (Tahir et al. 2017). This first study on T. huangmeiensis based on morphological features using light microscopy and small subunit ribosomal DNA sequence (Tahir et al. 2017), suggested that more detailed descriptions on the physiological and structural changes of this species should be done. Thus, in this study, we looked at the ultrastructures of T. huangmeiensis using electron microscopy, including both scanning (SEM) and transmission electron microscopy (TEM). 

Sporophytes, megaspores, and massulae of Azolla stanleyi from the Paleocene Joffre Bridge locality, Alberta

1994 ◽  
Vol 72 (3) ◽  
pp. 301-308 ◽  
Author(s):  
Georgia L. Hoffman ◽  
Ruth A. Stockey
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Key Words ◽  
Red Deer ◽  
The Other ◽  
Evolutionary Trends ◽  
Reproductive Structures ◽  
Transmission Electron ◽  
New Material

Several hundred vegetative and fertile specimens of Azolla Lam. have been recovered from the Paleocene Paskapoo Formation at the Joffre Bridge locality (Middle Tiffanian (Ti3) age) near Red Deer, Alberta. The spore complexes closely resemble those of the Paleocene A. stanleyi Jain & Hall, and the vegetative material is referred to that species. The specimens are unusually complete in that the remains of the fragile sporophyte are preserved, commonly with reproductive structures in place. Plants reaching up to 2.25 cm in length consist of alternately branched rhizomes bearing alternate, imbricate, sessile leaves. Leaves are ovate with entire margins, papillate surfaces, and a single midvein. Reproductive structures have been examined using light, scanning, and transmission electron microscopy. This new material is compared with the other Paleocene species for which sporophytes are known and discussed in terms of evolutionary trends for the genus. The specimens suggest that most of the vegetative characteristics of modern Azolla species were established by the middle Paleocene. Key words: Azolla, Salviniaceae, megaspore, massula, ultrastructure, Paleocene.

Pollen morphology of Sabinaria magnifica (Cryosophileae, Coryphoideae, Arecaceae)

Phytotaxa ◽  
2015 ◽  
Vol 207 (1) ◽  
pp. 135 ◽  
Author(s):  
Giovanni Raul Bogota ◽  
Carina Hoorn ◽  
Wim Star ◽  
Rob Langelaan ◽  
Hannah Banks ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Light Microscopy ◽  
Pollen Morphology ◽  
Pollen Grains ◽  
The Other ◽  
Transmission Electron ◽  
Palm Species ◽  
Scanning Electron

Sabinaria magnifica is so far the only known species in the recently discovered tropical palm genus Sabinaria (Arecaceae). Here we present a complete description of the pollen morphology of this palm species based on light microscopy (LM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). We also made SEM-based comparisons of Sabinaria with other genera within the tribe Cryosophileae. Pollen grains of Sabinaria magnifica resemble the other genera in the heteropolar, slightly asymmetric monads, and the monosulcate and tectate exine with perforate surface. Nevertheless, there are some clear differences with Thrinax, Chelyocarpus and Cryosophila in terms of aperture and exine. S. magnifica differs from its closest relative, Itaya amicorum, in the exine structure. This study shows that a combination of microscope techniques is essential for the identification of different genera within the Cryosophileae and may also be a necessary when working with other palynologically less distinct palm genera. 

Conversion of platelets into dislocation loops and voidite formation in type IaB diamonds

1995 ◽  
Vol 449 (1936) ◽  
pp. 295-313 ◽  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Local Mode ◽  
Diamond Structure ◽  
Dislocation Loops ◽  
X Ray ◽  
Regular Type ◽  
Transmission Electron ◽  
Stable Conditions ◽  
The One

Type la natural diamonds have been heated in the temperature range of 2400-2700°C under stabilizing pressures. The specimens studied are mainly regular type IaB diamonds. Transmission electron microscopy studies of treated speci­mens show that platelets are converted to interstitial ½ a 0 <011> dislocation loops; voidites are also formed. When all the platelets have been converted, the ex­perimental features associated with them also disappear, i. e. the X-ray extra reflections (spikes), the B' local-mode absorption and the lattice absorption in the one-phonon region termed the D spectrum. It is discovered that when diamonds are heated under graphite-stable rather than diamond-stable conditions, the rate of conversion is considerably enhanced; for instance, at 2650°C there is an increase in the rate of about three orders of magnitude. This enhancement is considered to be due to the instability of the diamond structure itself and a reason for this enhancement is suggested.

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