Polarity-induced changes in the nanoindentation response of GaAs

2004 ◽  
Vol 19 (1) ◽  
pp. 131-136 ◽  
Author(s):  
E. Le Bourhis ◽  
G. Patriarche ◽  
L. Largeau ◽  
J.P. Rivière
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Plastic Zone ◽  
Room Temperature ◽  
Large Range ◽  
Load Range ◽  
Transmission Electron ◽  
Polar Surfaces ◽  
Induced Changes ◽  
Hardness Values

We studied the polarity-induced changes in the nanoindentation response of GaAs{111}. The nanoindentations were made under a large range of loads (Fmax between 0.2 mN and 50 mN) at room temperature on {111} faces of A (Ga) or B (As) character. The loading–unloading curves were compared first, with special attention addressed to pop-in events and hardness values (reported previously for microindentation). Transmission electron microscopy was used to observe the nanoindentation structures generated at the two polar surfaces. The size of the dense plastic zone generated around the indent site was found to increase linearly with √Fmax and similarly for both polar surfaces. The indentation rosettes possess a threefold symmetry with arms developed along the <110> directions parallel to the surface. Sizes were found to be very close for both polar surfaces and the entire load range. For an A-polar face, the rosette arms are constituted by two arms: a long arm (LA, α dislocations) and a short arm (β dislocations). At the B surface, only the LA (β dislocations) are formed. Furthermore, microtwinning was observed only for an A-polar face, similar to previous observations of anisotropic microtwinning at GaAs(001) surfaces.

Dislocations Produced by Indentation Deformation of HPVE GaN Films

2000 ◽  
Vol 622 ◽  
Author(s):  
M. H. Hong ◽  
P. Pirouz ◽  
P. M. Tavernier ◽  
D. R. Clarke
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Plastic Zone ◽  
Room Temperature ◽  
Prism Plane ◽  
Weak Beam ◽  
Transmission Electron ◽  
Hardness Tests ◽  
Increasing Temperature ◽  
Gan Film

ABSTRACTVickers hardness tests on {0001} and (1120) faces of a relatively thick GaN film grown on a (0001) sapphire substrate have been performed in the temperature range 25-1200°C. The microstructure of the plastic zone around the indentation sites has been investigated by transmission electron microscopy (TEM). At room temperature, the hardness was measured to be 12.3 GPa on the basal plane, and 11.1 GPa on the prism plane. The hardness decreases gradually with increasing temperature up to ∼800°C and then shows a plateau between ∼800 and ∼1050°C after which it decreases again above ∼1100°C. In contrast to the rather straight dislocations produced by room-temperature indentation of the (0001) face, the dislocations generated by indenting the (1120) face at room temperature were curved and in the shape of half-loops emanating from the indentation sites on the prism planes. Such dislocations were not dissociated within the resolution of weak-beam TEM.

Scanning and Transmission Electron Microscopy of Human Red Blood Cells

1969 ◽  
Vol 27 ◽  
pp. 44-45
Author(s):  
A.J. Tousimis ◽  
T.R. Padden
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Blood Cells ◽  
Room Temperature ◽  
Type Specimen ◽  
New Combination ◽  
Human Red Blood Cells ◽  
Transmission Electron ◽  
Microscope Slides ◽  
Scanning Electron

The size, shape and surface morphology of human erythrocytes (RBC) were examined by scanning electron microscopy (SEM), of the fixed material directly and by transmission electron microscopy (TEM) of surface replicas to compare the relative merits of these two observational procedures for this type specimen.A sample of human blood was fixed in glutaraldehyde and washed in distilled water by centrifugation. The washed RBC's were spread on freshly cleaved mica and on aluminum coated microscope slides and then air dried at room temperature. The SEM specimens were rotary coated with 150Å of 60:40- gold:palladium alloy in a vacuum evaporator using a new combination spinning and tilting device. The TEM specimens were preshadowed with platinum and then rotary coated with carbon in the same device. After stripping the RBC-Pt-C composite film, the RBC's were dissolved in 2.5N HNO3 followed by 0.2N NaOH leaving the preshadowed surface replicas showing positive topography.

Formation of Dislocation Channels in Neutron Irradiated Molybdenum

1972 ◽  
Vol 30 ◽  
pp. 672-673
Author(s):  
S. Mahajan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ambient Temperature ◽  
Room Temperature ◽  
Channel Formation ◽  
Early Stages ◽  
Transmission Electron ◽  
Three Stages ◽  
Two Stages ◽  
Polycrystalline Molybdenum

The evolution of dislocation channels in irradiated metals during deformation can be envisaged to occur in three stages: (i) formation of embryonic cluster free regions, (ii) growth of these regions into microscopically observable channels and (iii) termination of their growth due to the accumulation of dislocation damage. The first two stages are particularly intriguing, and we have attempted to follow the early stages of channel formation in polycrystalline molybdenum, irradiated to 5×1019 n. cm−2 (E > 1 Mev) at the reactor ambient temperature (∼ 60°C), using transmission electron microscopy. The irradiated samples were strained, at room temperature, up to the macroscopic yield point.Figure 1 illustrates the early stages of channel formation. The observations suggest that the cluster free regions, such as A, B and C, form in isolated packets, which could subsequently link-up to evolve a channel.

A crystallographic analysis of the CoSi/Si(111) interface using Transmission Electron Microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 574-575
Author(s):  
A.C. Daykin ◽  
C.J. Kiely ◽  
R.C. Pond ◽  
J.L. Batstone
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Defect Structure ◽  
Room Temperature ◽  
Theoretical Method ◽  
Crystallographic Analysis ◽  
Si Substrate ◽  
Transmission Electron ◽  
Theoretical Predictions

When CoSi2 is grown onto a Si(111) surface it can form in two distinct orientations. A-type CoSi2 has the same orientation as the Si substrate and B-type is rotated by 180° degrees about the [111] surface normal.One method of producing epitaxial CoSi2 is to deposit Co at room temperature and anneal to 650°C.If greater than 10Å of Co is deposited then both A and B-type CoSi2 form via a number of intermediate silicides .The literature suggests that the co-existence of A and B-type CoSi2 is in some way linked to these intermediate silicides analogous to the NiSi2/Si(111) system. The phase which forms prior to complete CoSi2 formation is CoSi. This paper is a crystallographic analysis of the CoSi2/Si(l11) bicrystal using a theoretical method developed by Pond. Transmission electron microscopy (TEM) has been used to verify the theoretical predictions and to characterise the defect structure at the interface.

Synthesis and TEM study of Ag–In–(Eu, Ce) ternary approximants

2009 ◽  
Vol 224 (1-2) ◽  
Author(s):  
Kazue Nishimoto ◽  
Miki Muraki ◽  
Ryuji Tamura
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Room Temperature ◽  
Transmission Electron

AbstractTernary Ag–In–(Eu, Ce) 1/1 approximants are synthesized and their structures are studied by transmission electron microscopy (TEM). For both the approximants, superlattice spots are clearly observed at room temperature, and the superstructures of the Ag–In–(Eu, Ce) approximants are found to be similar to those of Cd

Preparation of Straight and Orderly Polypyrrole Microrods through Soft Template Methods

2011 ◽  
Vol 306-307 ◽  
pp. 679-683
Author(s):  
Li Bo Sun ◽  
Yuan Chang Shi ◽  
Lin Ya Chu ◽  
Bing Chang Zhang ◽  
Jiu Rong Liu
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Cetyltrimethylammonium Bromide ◽  
Growth Process ◽  
Room Temperature ◽  
Oxidative Polymerization ◽  
Soft Template ◽  
Microemulsion System ◽  
Transmission Electron ◽  
The Impact

The straight and orderly microrods of polypyrrole(PPy) was synthesized in a microemulsion system consisted of cetyltrimethylammonium bromide(CTAB), n-pentanol, water and pyrrole by chemical oxidative polymerization, in which CTAB was used as soft templates and APS was used as the oxidant. Fourier-transform infrared spectroscopy (FTIR) was used to characterize the structure of the PPy microrods. Transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) was used to characterize the morphology of the samples. We discussed the impact of temperature, the adding way of the oxidant, the amount of cosurfactant n-pentanol to the morphology of PPy microrods. The results showed that straight and orderly PPy microrods with a diameter about 300nm and a length up to 20μm were synthesized when the temperature was kept at room temperature (25°C), the dropping time of APS was more than 1.5h, the ratio of CTAB to n-pentanol was 0.6:1, and the polymerization time was about 24h. We studied the growth process of PPy microrods by HTEM analysis. HTEM images revealed that the growth process of PPy changed from hollow microrods, semi-hollow microrods, and finally solid microrods.

Nanotwinned Surface on a Ternary Titanium Alloy with Increased Hardness Induced under Nanoindentations

2016 ◽  
Vol 874 ◽  
pp. 323-327
Author(s):  
Hong Xiu Zhou ◽  
Ming Lei Li ◽  
Neng Dong Duan ◽  
Bo Wang ◽  
Zhi Feng Shi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Surface Roughness ◽  
Titanium Alloy ◽  
Chemical Mechanical Polishing ◽  
Material Removal ◽  
Room Temperature ◽  
Chemical Reagents ◽  
Transmission Electron ◽  
High Temperature High Pressure

A nanotwinned surface is formed on a titanium alloy under nanoindentations. Prior to nanoindentation, blocks of a ternary titanium alloy are machined by chemical mechanical polishing. The surface roughness Ra and peak-to-valley values are 1.135 nm and 8.82 nm, respectively. The hardness in the indented surface is greatly increased, indicated from the load-displacement curves compared to the polished surfaces. Nanotwins are confirmed using transmission electron microscopy. The nanotwinned surface is uniformly generated by nanoindentations at room temperature, which is different from previous findings, in which high temperature, high pressure, or chemical reagents are usually used. The nanotwinned surface is produced by pure mechanical stress, neither material removal nor addition.

scholarly journals In situ environmental HRTEM discloses low temperature carbon soot oxidation by ceria–zirconia at the nanoscale

2019 ◽  
Vol 55 (27) ◽  
pp. 3876-3878 ◽  
Author(s):  
Eleonora Aneggi ◽  
Jordi Llorca ◽  
Alessandro Trovarelli ◽  
Mimoun Aouine ◽  
Philippe Vernoux
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Low Temperature ◽  
Room Temperature ◽  
Soot Oxidation ◽  
Environmental Transmission ◽  
Transmission Electron ◽  
Carbon Soot ◽  
Environmental Transmission Electron Microscopy

In situ environmental transmission electron microscopy discloses room temperature carbon soot oxidation by ceria–zirconia at the nanoscale.

Strengthening Mechanism and Thermal Stability of Spray Formed H13 Steel

2019 ◽  
Vol 295 ◽  
pp. 49-56
Author(s):  
Zhan Zhan Zhang ◽  
Wan Zhen Wang ◽  
Yun Bo Chen ◽  
Miao Hui Wang ◽  
Chang De Zhao ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thermal Stability ◽  
Transmission Electron Microscopy ◽  
Strengthening Mechanism ◽  
H13 Steel ◽  
Tempering Temperature ◽  
Transmission Electron ◽  
Tempering Treatment ◽  
Hardness Values ◽  
Thermal Stability Of

The aim of this work is to study the strengthening mechanism and thermal stability of spray formed H13 steel. The microstructure and hardness of spray formed H13 steels are investigated by electron microscopy, transmission electron microscopy and hardness measurementscanning. The calculated results demonstrate that tensile strength, impact energy and hardness values of sprayed-formed H13 steel are higher than that of as-cast H13 steel when the tempering temperature is 600 °C after quenched at 1050 °C. Compared with as-cast H13 steels, tempered spray-formed H13 steels possess supernal high-temperature temper resistant stability. The chemical composition of the carbides in spray-formed steels is V and Cr rich spherical carbides are hardly influenced by the tempering treatment.

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