Tip induced changes of atomic scale images of the vanadiumpentoxide surface

1996 ◽  
Vol 348 (3) ◽  
pp. 305-310 ◽  
Author(s):  
R.A. Goschke ◽  
K. Vey ◽  
M. Maier ◽  
U. Walter ◽  
E. Goering ◽  
...  
Keyword(s):  
2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Corey J. Cochrane ◽  
Jordana Blacksberg ◽  
Mark A. Anders ◽  
Patrick M. Lenahan

Abstract Magnetometers are essential for scientific investigation of planetary bodies and are therefore ubiquitous on missions in space. Fluxgate and optically pumped atomic gas based magnetometers are typically flown because of their proven performance, reliability, and ability to adhere to the strict requirements associated with space missions. However, their complexity, size, and cost prevent their applicability in smaller missions involving cubesats. Conventional solid-state based magnetometers pose a viable solution, though many are prone to radiation damage and plagued with temperature instabilities. In this work, we report on the development of a new self-calibrating, solid-state based magnetometer which measures magnetic field induced changes in current within a SiC pn junction caused by the interaction of external magnetic fields with the atomic scale defects intrinsic to the semiconductor. Unlike heritage designs, the magnetometer does not require inductive sensing elements, high frequency radio, and/or optical circuitry and can be made significantly more compact and lightweight, thus enabling missions leveraging swarms of cubesats capable of science returns not possible with a single large-scale satellite. Additionally, the robustness of the SiC semiconductor allows for operation in extreme conditions such as the hot Venusian surface and the high radiation environment of the Jovian system.


2015 ◽  
Vol 1094 ◽  
pp. 168-173
Author(s):  
Xiu E Ren ◽  
Jian Hui Zhang ◽  
Xiao Dan Lv ◽  
Qi Dan Chen

Preferential adsorption takes place at the step ledge between adjacent crystal faces, which usually serve as active sites for breaking chemical bonds. In this paper, we present a structural model to interpret the habit modification of single crystals in terms of the step geometries relationship between crystal faces. A new series of high index faces parallel to the ledge between adjacent facets can be explicitly determined from the presence of the symmetry operators in the space group. The relative stability of these new faces undergoes a faceting transition, driven by the adsorbate-induced changes of the step configuration. Combined with the chemical bond-geometric approach, our predictions accurately reproduce the tapering evolutions of KDP crystals in the present of metallic ions. The current work provides a new insight on how changes affecting elementary steps on one face are translated into the emergence of a new crystallographic face.


2021 ◽  
Author(s):  
Nidhin Thomas ◽  
Ashutosh Agrawal

We report evidence of lateral electric field-induced changes in the phase transition temperatures of lipid bilayers. Our atomic scale molecular dynamics simulations show that lateral electric field increases the melting temperature of DPPC, POPC and POPE bilayers. Remarkably, this shift in melting temperature is only induced by lateral electric field, and not normal electric field. This mechanism could provide new mechanistic insights into lipid-lipid and lipid-protein interactions in the presence of endogenous and exogenous electric fields.


2012 ◽  
Vol 3 (19) ◽  
pp. 2845-2850 ◽  
Author(s):  
Zhenxing Feng ◽  
Lei Cheng ◽  
Chang-Yong Kim ◽  
Jeffrey W. Elam ◽  
Zhan Zhang ◽  
...  

Author(s):  
E. Knapek ◽  
H. Formanek ◽  
G. Lefranc ◽  
I. Dietrich

A few years ago results on cryoprotection of L-valine were reported, where the values of the critical fluence De i.e, the electron exposure which decreases the intensity of the diffraction reflections by a factor e, amounted to the order of 2000 + 1000 e/nm2. In the meantime a discrepancy arose, since several groups published De values between 100 e/nm2 and 1200 e/nm2 /1 - 4/. This disagreement and particularly the wide spread of the results induced us to investigate more thoroughly the behaviour of organic crystals at very low temperatures during electron irradiation.For this purpose large L-valine crystals with homogenuous thickness were deposited on holey carbon films, thin carbon films or Au-coated holey carbon films. These specimens were cooled down to nearly liquid helium temperature in an electron microscope with a superconducting lens system and irradiated with 200 keU-electrons. The progress of radiation damage under different preparation conditions has been observed with series of electron diffraction patterns and direct images of extinction contours.


Author(s):  
Sarah A. Luse

In the mid-nineteenth century Virchow revolutionized pathology by introduction of the concept of “cellular pathology”. Today, a century later, this term has increasing significance in health and disease. We now are in the beginning of a new era in pathology, one which might well be termed “organelle pathology” or “subcellular pathology”. The impact of lysosomal diseases on clinical medicine exemplifies this role of pathology of organelles in elucidation of disease today.Another aspect of cell organelles of prime importance is their pathologic alteration by drugs, toxins, hormones and malnutrition. The sensitivity of cell organelles to minute alterations in their environment offers an accurate evaluation of the site of action of drugs in the study of both function and toxicity. Examples of mitochondrial lesions include the effect of DDD on the adrenal cortex, riboflavin deficiency on liver cells, elevated blood ammonia on the neuron and some 8-aminoquinolines on myocardium.


Author(s):  
H. Hashimoto ◽  
Y. Sugimoto ◽  
Y. Takai ◽  
H. Endoh

As was demonstrated by the present authors that atomic structure of simple crystal can be photographed by the conventional 100 kV electron microscope adjusted at “aberration free focus (AFF)” condition. In order to operate the microscope at AFF condition effectively, highly stabilized electron beams with small energy spread and small beam divergence are necessary. In the present observation, a 120 kV electron microscope with LaB6 electron gun was used. The most of the images were taken with the direct electron optical magnification of 1.3 million times and then magnified photographically.1. Twist boundary of ZnSFig. 1 is the image of wurtzite single crystal with twist boundary grown on the surface of zinc crystal by the reaction of sulphur vapour of 1540 Torr at 500°C. Crystal surface is parallel to (00.1) plane and electron beam is incident along the axis normal to the crystal surface. In the twist boundary there is a dislocation net work between two perfect crystals with a certain rotation angle.


Author(s):  
R. J. Wilson ◽  
D. D. Chambliss ◽  
S. Chiang ◽  
V. M. Hallmark

Scanning tunneling microscopy (STM) has been used for many atomic scale observations of metal and semiconductor surfaces. The fundamental principle of the microscope involves the tunneling of evanescent electrons through a 10Å gap between a sharp tip and a reasonably conductive sample at energies in the eV range. Lateral and vertical resolution are used to define the minimum detectable width and height of observed features. Theoretical analyses first discussed lateral resolution in idealized cases, and recent work includes more general considerations. In all cases it is concluded that lateral resolution in STM depends upon the spatial profile of electronic states of both the sample and tip at energies near the Fermi level. Vertical resolution is typically limited by mechanical and electronic noise.


Author(s):  
L. T. Germinario

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.


Author(s):  
Alexis T. Bell

Heterogeneous catalysts, used in industry for the production of fuels and chemicals, are microporous solids characterized by a high internal surface area. The catalyticly active sites may occur at the surface of the bulk solid or of small crystallites deposited on a porous support. An example of the former case would be a zeolite, and of the latter, a supported metal catalyst. Since the activity and selectivity of a catalyst are known to be a function of surface composition and structure, it is highly desirable to characterize catalyst surfaces with atomic scale resolution. Where the active phase is dispersed on a support, it is also important to know the dispersion of the deposited phase, as well as its structural and compositional uniformity, the latter characteristics being particularly important in the case of multicomponent catalysts. Knowledge of the pore size and shape is also important, since these can influence the transport of reactants and products through a catalyst and the dynamics of catalyst deactivation.


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