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 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.

scholarly journals A “Pushy” Microscope

1996 ◽  
Vol 4 (2) ◽  
pp. 3-4
Author(s):  
Stephen W. Carmichael
Keyword(s):  
Scanning Tunneling Microscope ◽  
Low Temperatures ◽  
Research Laboratory ◽  
Room Temperature ◽  
Scientific Research ◽  
Thermal Motion ◽  
Scanning Tunneling ◽  
Two Dimensional ◽  
Tunneling Microscope ◽  
Dimensional Surface

The process of ultra-miniaturization has been termed nanofabrication. It looks like the scanning tunneling microscope (STU) and related microscopes will be players in this technology of the future. One of the most recent contributions has been the demonstration that single molecules can be “pushed” across a surface with the STM. This remarkable achievement was demonstrated by Thomas Jung, Reto Schlittler, and James Gimzewski of the IBM Zurich Research Laboratory and Hao Tang and Christian Joachim of the National Center for Scientific Research in Toulouse, They were able to position intact individual molecules on a two-dimensional surface at room temperature by a controlled “pushing” action of the tip of a STM. Similar positioning feats have been done at low temperatures while thermal motion is limited.

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.

ROOM TEMPERATURE TUNNELING CHARACTERISTICS OF ULTRA-SMALL NORMAL JUNCTIONS

1992 ◽  
Vol 06 (05) ◽  
pp. 273-280 ◽  
Author(s):  
M.D. REEVE ◽  
O.G. SYMKO ◽  
R. LI
Keyword(s):  
Scanning Tunneling Microscope ◽  
Coulomb Blockade ◽  
Room Temperature ◽  
Tunnel Junctions ◽  
Electron Tunneling ◽  
Single Electron ◽  
Scanning Tunneling ◽  
Tunneling Microscope ◽  
Single Electron Tunneling ◽  
Coulomb Staircase

Tunneling studies between a Scanning Tunneling Microscope (STM)-controlled fine NbN tip and a NbN thin film show single electron tunneling characteristics at room temperature. The I-V curves display the Coulomb blockade and the Coulomb staircase caused by single electron charging of a series combination of two tunnel junctions. These room temperature observations indicate that it may be possible to operate single-electron-based devices in non-cryogenic regimes.

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