Scanning tunneling microscope observations of the mirror region of silicate glass fracture surfaces

1994 ◽  
Vol 9 (2) ◽  
pp. 476-485 ◽  
Author(s):  
D.M. Kulawansa ◽  
L.C. Jensen ◽  
S.C. Langford ◽  
J.T. Dickinson ◽  
Yoshihisa Watanabe
Keyword(s):  
Scanning Tunneling Microscope ◽  
Soda Lime ◽  
Local Deformation ◽  
Fused Silica ◽  
Scanning Tunneling ◽  
Soda Lime Glass ◽  
Self Similarity ◽  
Tunneling Microscope ◽  
Fracture Surfaces ◽  
Mirror Region

We report scanning tunneling microscope images of gold-coated fracture surfaces of soda lime glass and fused silica in the mirror region. The scans show a variety of nanometer scale features that are attributed to fracture phenomena at this scale. We find considerable similarity to the structures observed in regions of extensive crack branching (e.g., “mist”). The density of these features increases as one progresses away from the crack origin toward the mirror-mist boundary. Comparisons are made between soda lime glass and fused silica, revealing differences in the local deformation behavior of these two materials. Self-similarity of the observed structures is probed by measurements of the fractal dimension, Df, of the surfaces created in soda lime glass near the mirror-mist boundary, where we observe 2.17 > Df > 2.40.

Scanning tunneling microscope observations of metallic glass fracture surfaces

1993 ◽  
Vol 8 (10) ◽  
pp. 2543-2553 ◽  
Author(s):  
D.M. Kulawansa ◽  
J.T. Dickinson ◽  
S.C. Langford ◽  
Yoshihisa Watanabe
Keyword(s):  
Fracture Surface ◽  
Metallic Glass ◽  
Metallic Glasses ◽  
Scanning Tunneling Microscope ◽  
Shear Bands ◽  
Scanning Tunneling ◽  
Tunneling Microscope ◽  
Fracture Surfaces ◽  
Glass Fracture ◽  
Shear Instabilities

We report scanning tunneling microscope observations of fracture surfaces formed during catastrophic crack growth in three metallic glasses: Ni56Cr18Si22B4, Co69Fe4Ni1Mo2B12Si12, and Fe78B13Si9. Macroscopically, the first two glasses fail along a slip band formed during loading and display a characteristic, μm-scale pattern of vein-like ridges; in contrast, Fe78B13Si9 displays little slip prior to fracture, and its fracture surface shows a μm-scale chevron pattern of steps. STM observations of fracture surfaces of all three materials show nm-scale grooves. The grooves in Co69Fe4Ni1Mo2B12Si12 are especially prominent and display stepped edges which we attribute to the intersection of shear bands with the surface. STM observations of the vein-like features on Ni56Cr18Si22B4 also show stepped edges. We attribute the vein features to the interaction of adjacent crack fingers in which the material between adjacent fingers fails in plane stress. The origin of the grooves is uncertain, but may be due to other shear instabilities along crack fingers.

Scanning tunneling microscope observations of polymer fracture surfaces

1992 ◽  
Vol 7 (5) ◽  
pp. 1292-1302 ◽  
Author(s):  
D.M. Kulawansa ◽  
S.C. Langford ◽  
J.T. Dickinson
Keyword(s):  
Crack Growth ◽  
Scanning Tunneling Microscope ◽  
Room Temperature ◽  
Slow Crack Growth ◽  
Liquid Nitrogen Temperature ◽  
Scanning Tunneling ◽  
Tunneling Microscope ◽  
Fracture Surfaces ◽  
Polymer Fracture ◽  
Double Torsion

Scanning tunneling microscope observations of gold-coated polymer fracture surfaces are reported. We compare nm-scale surface features of poly(methyl methacrylate) (PMMA) fractured under three different loading conditions: in tension at room temperature, in tension at liquid nitrogen temperature, and in the double torsion geometry at room temperature (slow crack growth). Fracture surfaces of polystyrene and polycarbonate loaded in tension at room temperature are also described. Each of these surfaces shows distinctive nm-scale features which we interpret in terms of the interaction between craze growth (fibril formation) and crack growth along the craze boundary. The resolution of these images is sufficient to greatly complement other fractographic studies.

Scanning tunneling microscopy of E. coli RNA polymerase deposited onto an Au substrate by an electrochemical process

1991 ◽  
Vol 49 ◽  
pp. 378-379
Author(s):  
Rebecca W. Keller ◽  
Carlos Bustamante ◽  
David Bear
Keyword(s):  
Scanning Tunneling Microscope ◽  
Biological Sample ◽  
Substrate Surface ◽  
Electrochemical Process ◽  
Atomic Resolution ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Tunneling Microscope ◽  
E Coli ◽  
Preparation Techniques

Under ideal conditions, the Scanning Tunneling Microscope (STM) can create atomic resolution images of different kinds of samples. The STM can also be operated in a variety of non-vacuum environments. Because of its potentially high resolution and flexibility of operation, it is now being applied to image biological systems. Several groups have communicated the imaging of double and single stranded DNA.However, reproducibility is still the main problem with most STM results on biological samples. One source of irreproducibility is unreliable sample preparation techniques. Traditional deposition methods used in electron microscopy, such as glow discharge and spreading techniques, do not appear to work with STM. It seems that these techniques do not fix the biological sample strongly enough to the substrate surface. There is now evidence that there are strong forces between the STM tip and the sample and, unless the sample is strongly bound to the surface, it can be swept aside by the tip.

STM of freeze-fracture replicas: Problems and promises

1993 ◽  
Vol 51 ◽  
pp. 68-69
Author(s):  
J. T. Woodward ◽  
J. A. N. Zasadzinski
Keyword(s):  
Scanning Tunneling Microscope ◽  
Organic Materials ◽  
Freeze Fracture ◽  
Atomic Resolution ◽  
Scanning Tunneling ◽  
Tunneling Microscope ◽  
Molecular Scale ◽  
Organic Surfaces ◽  
Metal Layers ◽  
Conductive Surfaces

The Scanning Tunneling Microscope (STM) offers exciting new ways of imaging surfaces of biological or organic materials with resolution to the sub-molecular scale. Rigid, conductive surfaces can readily be imaged with the STM with atomic resolution. Unfortunately, organic surfaces are neither sufficiently conductive or rigid enough to be examined directly with the STM. At present, nonconductive surfaces can be examined in two ways: 1) Using the AFM, which measures the deflection of a weak spring as it is dragged across the surface, or 2) coating or replicating non-conductive surfaces with metal layers so as to make them conductive, then imaging with the STM. However, we have found that the conventional freeze-fracture technique, while extremely useful for imaging bulk organic materials with STM, must be modified considerably for optimal use in the STM.

The atomic-force microscope and its future in biology

1993 ◽  
Vol 51 ◽  
pp. 704-705
Author(s):  
Jean-Paul Revel
Keyword(s):  
Silicon Nitride ◽  
Laser Beam ◽  
Atomic Force Microscope ◽  
Scanning Tunneling Microscope ◽  
Point Of View ◽  
Scanning Tunneling ◽  
Close Relative ◽  
Tunneling Microscope ◽  
Atomic Force ◽  
Sharp Point

The last few years have been marked by a series of remarkable developments in microscopy. Perhaps the most amazing of these is the growth of microscopies which use devices where the place of the lens has been taken by probes, which record information about the sample and display it in a spatial from the point of view of the context. From the point of view of the biologist one of the most promising of these microscopies without lenses is the scanned force microscope, aka atomic force microscope.This instrument was invented by Binnig, Quate and Gerber and is a close relative of the scanning tunneling microscope. Today's AFMs consist of a cantilever which bears a sharp point at its end. Often this is a silicon nitride pyramid, but there are many variations, the object of which is to make the tip sharper. A laser beam is directed at the back of the cantilever and is reflected into a split, or quadrant photodiode.

FIELD ION MICROSCOPE AND ATOM-PROBE STUDIES OF SCANNING TUNNELING MICROSCOPE TIPS

1988 ◽  
Vol 49 (C6) ◽  
pp. C6-55-C6-59 ◽  
Author(s):  
O. NISHIKAWA ◽  
K. HATTORI ◽  
F. KATSUKI ◽  
M. TOMITORI
Keyword(s):  
Scanning Tunneling Microscope ◽  
Atom Probe ◽  
Scanning Tunneling ◽  
Tunneling Microscope ◽  
Field Ion Microscope
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